Small is BIG

Iodometric titration on paper device #PADs

2015-03-13T14:47:00.001-06:00

Titration technique is widely used in various analytical service providing and teaching laboratories. In this technique, a solution of known concentration is used to determine the concentration of an unknown sample. The currently used titration methods consume large volume of reagents and samples (hundreds of milliliter) and glassware like burette and pipettes.

Design of iodometric paper test card (source)

Titrations now can be carried out in a piece of paper modified with appropriate reagents. Professor Lieberman's group from University of Notre Dame recently has described an iodometric titration method in a paper card-published in Analytical Chemistry journal. Titration in the paper test card starts by applying a test solution to the test card in which multiple dried reagents have been stored separately. The reagents reconstitute and combine through a surface-tension enabled mixing (STEM) after the application of unknown solution. The end point of the titration is indicated by the appearance of blue complex of iodide and starch. The signal can also quantitated by using image-processing software.

Iodometric titration involves a redox reaction used to determine the amount of variety of analytes of interests. The authors used this method to quantitate the iodine present in common salt and also demonstrated the versatility of the titration device by quantifying beta-lactam antibiotics via an iodometric back-titration. In later example, the antibiotic was degraded in base to obtain a redox active thiol. The reaction mixture was then acidified and a known amount of excess triiodide is added to oxidize the thiol. Ureacted triiodide is back-titrated with thiosulfate.

 Unique feature of the iodometric test card is its ability to store multiple reagents separately for long time and allowing them to mix and react when desired.

 The paper titration technique would be very useful in developing countries and in remote locations-especially. It is cheap, easy to perform and requires small amount of reagents. Also, generates less waste. Authors described the stability of this test card (stored reagents) for ~20 days at temperature 40deg C. It is not clear if the results obtained at above conditions will be valid for more than 20 days and higher temperature combined with humidity. Lets consider a village in India. Some of the Indian villages see temperatures more than 40 deg C (easily 45) that combined with high percentage of humidity. Will the test card work in this location? Proper packaging can protect effect of humidity, however. If the test card is not manufactured at local level, then 20 days time frame is not enough. It will take months for the cards to be used in field.

This method has great scope to be introduced in to the classroom-teaching labs.

Will this new method replace traditional ways of doing iodometric titrations?

Acid-base titration on paper microfluidic device: will it replace traditional acid-base titration?

2015-01-25T17:56:00.002-07:00

u-PAD for acid-base titration (source)

Research in paper-based microfluidic analytical devices (u-PADs) has evolved very fast in past couple of years. Recently, scientists from Okayama University, Japan have reported a technique to carry out acid-base titrations in PADs and the work has been published in journal Analytical Chemistry.

The wax printed u-PADs consisted of ten reaction (acid-base reaction) and 10 detection reservoirs. The detection reservoirs were applied with a constant amount of phenolphthalein (indicator) and the reaction reservoirs were applied with various amount of a primary standard potassium hydrogen phthalate (KHPth). Only less than a microliter volume of the solutions were needed. The base (e.g., NaOH) was dropped onto the center reservoir of the device. As the base wicked towards the reaction reservoir, it then reacted with the acid and if any extra NaOH remained it then moved further and reached to the detection reservoir to produce a pink color. The number of detection reservoirs with no color change was used to determine the concentration of NaOH. The authors have tested this technique using other acids like nitric acid, hydrochloric acid, sulfuric acid, and acetic acid.

Acid-base titration is widely used in teaching chemistry and in variety of analytical services. The currently used titration methods involve large volume of reagents and samples; glassware (burette and pipettes).

The new u-PAD being used in field testing (source)

The new method takes only about a minute to complete the titration and is more advantageous than classical titration methods in terms of speed, portability, and disposability.

Eventhough the micro-titration device was shown to be stable for couple of days, it requires further improvements to make the device stable for longer time. The reagents stored in the PADs degrade with time. Therefore the reagents have to be applied at the time of use only. Also, temperature plays bad role for the stability of the PADs. Therefore not suitable for places with higher ambient temperature (e.g., summer time in India).

As PADs are cheap, this new titration technique may replace the traditional titrations, specially in developing countries. Teaching settings can immediately adopt the technique.

How does Google Contact Lens Work?

2014-07-16T10:30:00.001-06:00

A prototype Google Contact Lens as Glucose sensor [source]

The Google contact lens is coming to reality. Google and Novartis announced on Monday that they will work together to bring this new technology to the public. Google[x] of Google has developed this technology, unveiled at first in January, that is supposed to measure the levels of glucose in tear. If everything goes as planned, we will see prototype product for research and development reviews by 2015.

Cartoon showing lens components

The soft contact lens consists of a wireless chip and a miniaturized glucose sensor housed in between two layers of lens material. The lens also features a tiny antenna, capacitor, and controller. Data is relayed via wireless antenna that is thinner than human hair.The information gathered from the lens can move from the eye to a device such as a handheld monitor, where that data can be read and analysed.

This is how the lens looks like.

There is a tiny pinhole in the lens. Tear fluid is seeped into the sensor which measures the glucose level. The electronics lie outside of both the pupil and the iris so there is no damage to the eye. The miniaturized sensor is powered by a wireless device which will communicate data via the wireless technology radio frequency identification (RFID). This wireless non-contact technology uses radio-frequency electromagnetic fields to transfer data.

This method will be an easier, pain free, and non-invasive alternative to currently used methods that require prick fingers for droplets of blood. The new technology can give you reading every second. The developers of this technology are also planning to add small LED lights that could warn you when the glucose levels cross certain threshold level that are critically harmful.

Apps developed for this technology would make the measurements available to the wearer and their doctor.

Google will ensure that any data transferred from the lens cannot be manipulated.

How to make glass microfluidics device? chemical wet etching and room temperature bonding

2014-07-10T09:34:00.002-06:00

[First part of this post is here where I wrote step by step procedure for mask design and photolithography.]

After completing the photolithographic procedure, we use two different solutions for selectively removing chromium and glass from the channel network on the bottom substrate.

Chemical wet etching solutions. On left is BOE with temperature control
and on right is Chrom etchant. Middle one is DI water.

At first, chromium layer from channel network is removed by immersing the substrate plate into a Teflon coated jar containing chromium etchant solution for about 15 min. One should note that leaving substrate plate in this solution for long time (hours and hours-this happens when you forget to remove it) could eat away even the photoresist layer from the entire plate. We buy the chrome etchant from Transene Company, INC, MA, USA and according to manufacturer specification the solution contains ceric sulfate (5-10%), nitric acid (5-10%), sulfuric Acid (1-5%), water (~ 75%). The entire substrate is then washed with DI water and dried by blowing N₂ gas. At this point one can clearly see through the substrate in channel patterning region.

Cartoon depicting the removal of photoresist and chromium layer from channel pattern

After this step, we cut the substrate into individual chips (1" x 2") using a glass-cutter (altogether 8 chips from one 8” x 8” substrate). Then, put extra layer of photoresist, dry in oven (80 ^o C), take out from the oven, and let it cool.

The substrate plate-individual chip is then immersed into a 1:10 buffered oxide etchant (BOE) solution bought from Transene Company, INC, MA, USA. According to the company specifications, this solution contains a mixture of hydrofluoric (HF) (1-25%), ammonium fluoride (NH₄F) (2-40%), distilled water. Hydrofluoric acid is a hazardous chemical, therefore must be handled with extra precaution. The BOE solution is continuously stirred at the rate of 120 rpm using a magnetic stirrer and the temperature is set at 55 ^oC. The substrate plate is removed from the BOE solution at a certain interval of time ~10-15 min (depending on the etching rate of BOE and channel depth desire), washed with DI water, and is dried with N₂. With our settings, etching rate is ~0.5 micron per minute.

However, this rate can be manipulated based on your need.

Cartoon showing the substrate plate after removing glass material.
Remember the glass etching is in all direction (not like in this cartoon)

The depth of the channel is measured using a XP series stylus profiler (Ambios Technology, CA, USA). This step is repeated until one gets desired channel depth.

Profiler

Once desired channel depth is obtained, ~1 mm diameter access holes were punched at the channel terminals using a microabrasive power blasting system (Vaniman) by blowing sand particles from back side of the substrate. The miroabrasive system utilizes mechanical erosion on the substrate by bombarding with high-kinetic energy sand particles and results in conically shaped holes. This step is followed by removing the photoresist and chromium layer on remaining parts of the bottom substrate by using acetone and chromium etchant, respectively.

Sandblaster

Bonding two glass plates: The etched channels in the bottom substrate were sealed using cover plate. The two plates (bottom substrate and cover plate) were cleaned and brought together in a beaker containing DI water for bonding. They were removed from the beaker together with a tweezer, water was removed by gently pressing the plates with hand in paper towel, and then put under couple of heavy books for ~2 hrs. Then the bonded chip was kept in an oven at 80 ^oC for ~1hrs to strengthen the bonding between two glass plates. Bonding is a crucial step to create closed fluidic microchip networks.

The bonding strength between two surfaces is proportional to the density of individual chemical bonds established between the two plates. Our bonding method is simple and does not require clean room facilities, programmed high-temperature furnaces, pressurized water sources, and adhesives. The bonding process can be completed in ~3 hrs. One of the most important factors affecting successful bonding of planner glass chips is the cleanliness of the bonding surfaces of glass substrates. Unsuccessful bonding events are often associated with solid particles or organic material remaining on the glass surfaces, for example, dust, residual photoresist, chromium or glass particles etc., prior to bonding. Some other critical factors for glass bonding are flatness of the glass plates and chip area.

Can Google glass test HIV and prostate cancer? #newtechnology

2014-05-05T02:08:00.001-06:00

Google Glass taking image of RDT
@ACSNANO

A Google Glass-based platform has been shown to detect human immunodeficiency virus (HIV) and prostate-specific antigen (PSA). Since its limited availability to public, Google Glass has been used for variety of applications.

The GoogleGlass is famous for a voice-controllable hands-free computing system that can perform imaging and video-recording tasks. In addition, various wireless technologies including Bluetooth and Wi-Fi are available in it. It can access internet and determine location information via global positioning systems (GPS) and/or triangulation through cellular service provider towers.

Google Glass @ACSNANO

The details of recently demonstrated Google Glass-based rapid diagnostic test (RDT) reader platform has been published in American Chemical Society journal ACSNANO by a group of scientists from University of California, LA, USA. This platform was used in lateral flow immunochromatographic assays that are important in biomedical diagnostic tests.

Without using any external optical hardware, the custom-written Glass application can take images of one or more RDTs labeled with QR codes in the lateral flow assay stripes developed for particular analytes using the built-in camera of the Glass. It then digitally transmits the images to a remote server for processing. The RDTs to be imaged can be either held in the user's hand or laid flat on a surface during imaging process. These digital test images are automatically processed to create a quantitative diagnostic result, which is then returned to the Google Glass user and stored with the RDT image and other related information on a central server providing review of diagnostics results via a world map through geo-tagged data.

This wearable computational platform like Google Glass allows for rapid hands-free imaging and processing of any number of RDTs. Such platforms would be very useful for disease and medical condition testing and monitoring in remote locations like places in Nepal, disaster relief areas, or quarantine zones especially in resource limited settings. Once this new application is fully optimized, it has a reasonably good potential for epidemiology and mobile-health applications. It may also be used in providing real-time spatiotemporal tracking of various diseases and personal medical conditions through a rapid hands-free and high-throughput imaging interface.

How to make glass microfluidic device? mask design and photolithography

2014-02-15T04:14:00.001-07:00

During my PhD at the University of Wyoming, I may have made ~400-500 microfluidic devices all from glass substrate. My PhD laboratory uses borosilicate based substrate/cover plate to make the chips for variety of applications such as immunoassay development, separation experiments, fuel cell units. Glass is one of the oldest materials in microfluidic field and has certain advantages (see below) over other materials that are being used in this field of research.

Inertness to many chemicals
Optical transparency
Low fluorescence
High resistance to mechanical stress
Well established surface modification procedures

Below are the steps taken for the fabrication of glass microfluidic device: starting from designing the channel network using CADopia software to bonding the glass plates. I will take you through each of these steps.

1. Mask design: We create a channel design using CAPopia drawing software. I had never used any drawing softwares before and found this one easy to use. Once the design is complete, we send it out to a printing company (Fineline Imaging, Colorado) to get the mask.

Mask with channel design

2. Photolithographic procedure: Once the photo-mask arrives from the printing company, we perform basic photo-lithography procedure to transfer the channel pattern design onto the glass substrate. We buy borosilicate glass substrate (Telic, CA, USA) which is 4” x 4” in dimension and 1.65 mm thick. One side of this glass substrate is coated with a layer of chromium and photoresist on top of each other. Both chromium and photoresist layers are about 100-200 nm in thickness. The photoresist coated on the substrate is polymer based positive photoresist which is sensitive to UV radiation. Therefore the box containing the substrate plates must be opened only in dark room.

In photolithography room turn on the UV light source before at least 15 min you plan to shine it to the substrate plate. We use a custom made box where one can place photo-mask on top of substrate plate. This assembly is then gently pressed by putting a glass plate on top of it. The whole thing is inside a box in which a shutter can be opened when ready to expose to UV radiation.

Typically we expose the substrate to the UV radiation for ~ 30-45sec. During this step the polymer of photoresist breaks down and is removed by soaking the substrate in a photo-developing solution (MF-319, Rohm and Haas) for ~ 5 min. The substrate is then washed with deionized (DI) water (DirectQ Water Purification System, Millipore) and dried by blowing N2 gas. After this washing step, one can clearly see the channel pattern on the glass substrate.

click HERE for second part of this post

ELISA with 100 fold improvement in detection limit & 100 fold less sample volume

2014-01-30T17:04:00.002-07:00

My first paper on microfluidic work has been published in Analitica Chimica Acta. This was the first project I worked on for my PhD work (actually the very first one didn't work. That was my advisor's crazy idea he wanted me to give a try. We abandoned that later on).

In this article, we have demonstrated a novel approach to enhancing the sensitivity of enzyme-linked immunosorbent assays (ELISA) through pre-concentration of the enzyme reaction product (resorufin/4- methylumbelliferone) in free solution.

Highly sensitive analytical techniques are required to estimate small amounts of disease markers (e.g., antibodies/antigens) in bodily fluids in order to detect the onset of dangerous diseases like cancers at their early stages. Here is the abstract of this paper.

The reported pre-concentration was accomplished by transporting the resorufin/4-methylumbelliferone molecules produced in the ELISA process towards a high ionic- strength buffer stream in a microfluidic channel while applying a voltage drop across this merging region. A sharp change in the electric field around the junction of the two liquid streams was observed to abruptly slow down the negatively charged resorufin/4-methylumbelliferone species leading to the reported pre- concentration effect based on the field amplified stacking (FAS) technique. It has been shown that the resulting enhancement in the detectability of the enzyme reaction product significantly improves the signal-to-noise ratio in the system thereby reducing the smallest detectable analyte concentration in the ELISA method. Applying the above-described approach, we were able to detect mouse anti-BSA and human TNF-a at concentrations nearly 60-fold smaller than that possible on commercial microwell plates. For the human TNF-a sample, this improvement in assay sensitivity corresponded to a limit of detec- tion (LOD) of 0.102 pg mL−1 using the FAS based microfluidic ELISA method as compared to 7.03 pg mL−1 obtained with the traditional microwell plate based approach. Moreover, because our ELISAs were per- formed in micrometer sized channels, they required sample volumes about two orders of magnitude smaller than that consumed in the latter case (1 uL versus 100 uL).

Microfluidic Approaches to Improving Enzyme-Linked Immunosorbent Assays

2013-12-07T15:25:00.000-07:00

This was the title of my PhD dissertation work. I successfully defended it on Tuesday. Now it feels really great!!! Just to give you some idea about my dissertation work, below is the general description of it. Details of the research work can be found in the dissertation which will be available online soon and in upcoming publications as journal articles.

Enzyme-linked immunosorbent assay (ELISA) is arguably one of the most practiced techniques used for reliable quantitation of biological analytes in complex sample matrices. The advantages of ELISA arise mainly from the specific interaction between an antigen and its corresponding antibody, and the signal amplification due to an enzyme reaction that produces multitude of detectable species per binding event of the target molecule to the assay surface. The conventional methods of performing ELISA are predominantly based on polystyrene microtiter plates that require relatively large amounts (~100 µL) of expensive and/or precious samples or reagents. This volume may not be large itself but it becomes an issue when one has to deal with expensive reagents and limited amount of sample. For example, analysis of multiple biomarkers from the content of a single cell. There is a need to miniaturize these ELISA methods. Moreover, the limited ability of this assay format to measure biomarker concentrations (e.g., antigens/antibodies) circulating in bodily fluids restricts its use in the detection of several fatal diseases (e.g., cancers) at an early stage. Therefore, there is a need to improve the minimum analyte concentration detectable (limit of detection) by these techniques. In addition to this insufficient assay sensitivity, the microtiter plate version of ELISA requires that the enzyme substrate undergoes a change in its spectral signature during the enzyme reaction necessitating that its fluorophore be acted upon by the enzyme-label. This constraint, in turn, limits the number of possible enzyme-substrate couples available for use in the ELISA method.

In my dissertation work, these major limitations of conventional ELISA methods have been addressed to broaden their utility in biomedical applications. The sample/reagent volume requirement of microtiter plate based ELISA has been reduced by simultaneously miniaturizing this assay and enhancing its multiplexing capabilities using the microfluidic platform. In an effort to improve the limit of detection, we have developed a pre-concentration ELISA method based on field amplified stacking of enzyme reaction product molecules in the ELISA micro-channel using two buffers of different ionic strengths.

In addition, we have demonstrated an ELISA method for the first time in which the enzyme substrate does not need to undergo a change in its spectral properties to allow its distinction from the enzyme reaction product in the assay chamber. We have accomplished this goal by synthesizing a rhodamine B based substrate molecule for the alkaline phosphatase enzyme-label, and then applying it to measuring the concentration of human TNF-α in a microfluidic device.

Lastly, a microfluidic method for simultaneous pre-concentration of cationic and anionic chemical species is described in my dissertation. This method is again based on the field amplified sample stacking process, and has been realized by injecting a relatively large plug of a sample prepared in a low-conductivity buffer into a microfluidic channel.

new trends in the application of paper based analytical devices

2013-09-26T15:43:00.000-06:00

Recently, I went to ACS Fall 2013 National meeting in Indianapolis. I presented two talks. My first talk was about a new microfluidic based ELISA (enzyme linked immunosorbent assay) method for measuring very low concentrations of protein markers and it was in a session called "portable instrumentation for chemical analysis". My second talk was about a new kind of enzyme substrate for ELISA applications and was in a session called "capillary and microfluidic platforms for bioanalytical measurements". Both sessions were under analytical chemistry division.

As I am more interested in paper based devices these days, I attended talks on low cost analytical devices primarily based on paper. Some talks by professors/students and more posters. I believe the research presented there will be seen more and more in future. Let me point out some of them.

1. paper based devices to monitor low quality pharmaceuticals and iodizing agents in salt.

PBAD used for testing pharmaceuticals. source: ACS

Professor Marya Lieberman and her group from the university of Notre Dame have developed paper based testing devices based on simple colorimetric chemistry. These devices are used to detect low quality pharmaceuticals, iodizing agents in salt etc. They have used these devices in really a low resource settings like in Kenya, Haiti, Iraq, India etc. The idea is that these devices can be sent out to every house/village to test whether the medicine (commonly used) contain what they are supposed to contain. In developing countries this is a very big problem. Prof Toni Barstis's group from Saint Mary's college is also working on paper based colorimetric devices that distinguishes between genuine and low quality anti-malaria ACT (artemisinin combination therapy) medications. The same group has also focused on identifying counterfeit drugs for river blindness.

2. paper based devices for detecting microorganism like bacteria, fungi etc.

One group in Canada are developing paper based culture devices for bacteria. Professor Carey's group from Taiwan are working on single step colorimetric sensing of human pathogenic bacteria in blood. Their paper device has an array of several dyes (proprietary) that give a signal when reacted from different metabolic by-products of bacteria. This produces kind of finger print to identify bacteria. When successful, this technique could come to market for regular bacteria assays. click here to see their recent publication. Similar to the work by Dr. Carey's group, a group from the University of Illinois at Urbana-Champaign have worked on differentiation and identification of pathogenic fungi based on colorimetric sensor array that reacts with the volatile organic compounds produced from fungi.

Prof Lu from Georgia Institute of Technology receives Anal Chem young innovator award 2013

2013-07-27T10:42:00.001-06:00

Prof Lu,
photo: Lu group website

Analytical Chemistry Young Innovator Award for 2013 is given to Prof. Hang Lu. She completed her MS and PhD in chemical engineering from MIT. Currently, she is a professor in the School of Chemical and Biomolecular Engineering, Georgia Institute of Technology.

Her group is working at the interface of engineering and biology to address questions in neuroscience, cell biology, and biotechnology.

According to announcement, this award is sponsored by Analytical Chemistry and the Chemical and Biological Microsystems Society (CBMS) and the award will be presented to the receipient at the Miniaturized Systems for Chemistry and Life Sciences (microTAS) conference, October 27-31, 2013 in Freiburg, Germany. Prof Lu was awarded for fundamental understanding and exploitation of fluid-, particle, cell, and organism-behavior at the micro scale and using micro-scale analytical chemical engineering for advances in neurogenetics, cell biology, and biotechnology.

Lu Fluidics Group

Congratulations Prof Lu.

no-instrument measurement in paper-based device

2013-05-04T13:54:00.002-06:00

Paper-based devices (PBDs) have emerged as a new class of inexpensive devices with potential use in medical diagnostics, environmental applications etc. They are not only inexpensive but also proven to be sensitive, quantitative, and reliable in many applications.

The colorimetric detection is one of the popular methods of quantitation of analytes in PBDs. Color developing reagents are used on the micro-reaction chambers on paper. The color developing reagent then reacts with the analyte of interest when the later is applied specifically and quantitatively. Simple and widely available instrumentations like a office scanner or a camera (could be a mobile phone camera) are used to capture the color which is then quantitated by measuring the signal using image processing software. If you don't have camera and/ or image processing software, don't worry. Scientists from Colorado State University have developed even a simpler method to quantitate analytes. This interesting work has recently been published in Lab on a Chip Journal.

The new technique relies on the length of the color developed. They call this as a simple distance-based detection. You just need a ruler to quantitate the analyte concentration: no camera, no scanner, no software.

How does this work?

First of all create a paper-based device. In their work, they have used wax printing to make PBDs. Their design has a straight channel, like a thermometer. There is one circular reservoir at one end. This reservoir is used for sample addition and/or transfer of analyte to the detection zone (long conduit).

Colorimetric detection reagents are deposited along the flow channel. They tested two different methods for this purpose: spray application or pipetting. Once the reagents are dry, the device is ready to use.

Sample solution in water is then added to the sample reservoir which flows into the detection/flow channel. The analyte reacts with reagent and develops color. Once all of the analyte is consumed, the color development stops. Analyte quantification is then done by measuring the length of the colored region in the detection zone by a ruler.

Authors of this paper have demonstrated their technique by measuring three different analytes: nickel, reduced glutathion, and glucose.

This new measurement technique is claimed to be accurate and sensitive compared to conventional methods.

In this figure, you can see that higher the concentration of analyte-the longer is the color developed region in detection zone.

shallow region on microchannel for better separation

2013-03-30T11:25:00.000-06:00

CZE technique, introduced in the 1960s, is used to separate charged analytes under the influence of an electric field. Charged analytes are separated on the basis of their size to charge ratio. Some of the applications of CZE include separation of DNA (e.g, in DNA fingerprinting), separation of proteins, analysis of basic drugs and related substances in pharmaceutical analysis etc.

Researchers from University of Wyoming have demonstrated that "shallow region" in a microfluidic separation duct enhances the resolving power of capillary zone electrophoresis (CZE). They have shown a 8 fold increase in resolving power while separating a mixture of amino acids utilizing this technique.

Simple microfluidic device to have better separation in CZE
as described by Xia and dutta (copied from Anal Chem)

In their recent article published in Analytical Chemistry, Prof Dutta and his student Ling used pressure driven back flow (counter flow to electroosmotic flow in the microchannel) to achieve their goal of high resolution CZE. This back flow was produced by a ~0.5 um deep shallow region. When electric field is applied on the separation channel, a mismatch in electroosmotic flow generates pressure driven back flow. Even though this back flow introduces some band broadening, overall increase in resolving power was better than a device without shallow region.

Authors claim to have following advantages in their device:

1. This device omits the use of an external pump for pressure generation simplifying its fabrication and operation;

2. It can readily be integrated into any detection and/or downstream analysis method; and

3. It is suitable for further miniaturization of the CZE technique to the submicrometer length scale.

link of article dx.doi.org/10.1021/ac302530y

Analyte preconcentration results in detecting lower concentrations of cancer marker

2013-03-27T21:50:00.003-06:00

It is important to detect lower concentrations of disease (like various cancers) markers in human bodily fluids reliably. The ability to detect lower analyte concentration would allow us to identify the onset of diseases in their early stages and start treatment process.

In an effort to make a device that could measure lower concentrations of protein, researchers of Dutta group at the University of Wyoming have developed a microfluidic device in which the analyte protein molecules are preconcentrated infront of membrane inside the channel. Enzyme Linked Immunosorbent Assay (ELISA) was performed on the same channel and the signal generated from the enzyme reaction was increased by a factor of 200.

In their current work reported, they have shown a reduction in the smallest detectable concentration of the tumor marker CA 199-9 and Blue tongue Viral antibody by over 2 orders of magnitude compared to immunoassays without preconcentration. This led to the improvement in the lowest analyte concentration detectable (LOD) by a factor of 20. Their device only required ~5 uL analyte and other solutions to complete the assay in contrast to conventional microtiter plate based assayed (~100uL).

There are several methods to amplify the ELISA signal and some of them involve preconcentration of enzyme reaction product (e.g resorufin) molecules. Dutta groups new method is unique in terms of preconcentrating target analyte-proteins. They used photopolymerized semipermeable membrane fabricated inside bonded glass microchip for preconcentrating analytes.

Details of this work has been published recently in Analytical Chemistry journal.

Laminar Flow in Microfluidics Devices

2013-02-08T22:04:00.000-07:00

Prof Kirby from Cornell University now has started producing videos of his class. Currently he directs the Micro/Nanofluidics Laboratory in the Sibley School of Mechanical and Aerospace Engineering. His research focuses on microbioanalytical devices, nanofiber textiles, nanoscale fluid mechanics, microparticle processing etc. He has also published books on micro- and nanoscale fluid mechanics from Cambridge University press.

In this post, I have put together his class videos on patterning microchannels using laminar flow. Laminar flow is a flow where liquid flows in parallel layers. In micro-channels this kind of flow is found (against turbulant flow in macroscale e.g., in rivers) so that two or more different solutions can flow in the same channel with mixing (only mixing by diffusion). This property of fluid in micro/nano domain can be exploited to pattern these systems. Prof Kirby teaches the theoritical basics of this phenomenon with examples/applications.

In the last video, he discusses about the Low-Re-High-Pe limit constraints for laminar flow patterning in microfluidics.

Affordable diagnostic tests for health problems

2013-01-17T13:18:00.003-07:00

JUST A DROP: This paper-based test, which costs less than $0.10, could help health care providers in developing countries monitor for liver toxicity associated with HIV and TB treatments.COURTESY OF DIAGNOSTICS FOR ALLPaper based devices getting popularity.

Human immunodeficiency virus (HIV) and tuberculosis (TB) are two of the leading killers in the world, taking an estimated 1.7 million and 1.4 million lives each year, respectively. The worldwide distribution of medications to treat these diseases has been a boon to global health, but some of those drugs can cause liver toxicity, so patients taking them need routine liver monitoring.

In developed countries, that’s simply a matter of visiting the doctor’s office and having blood drawn. With a whiz in an electric centrifuge and a quick pass through an automated machine to detect liver metabolites, the results are in. But in developing countries such as Botswana and South Africa—areas plagued by HIV and TB infections—such tests are virtually nonexistent. And there are no alternatives. “In a resource-limited setting, monitoring isn’t happening at all,” says Nira Pollock, associate director of the Infectious Diseases Diagnostic Laboratory at Boston Children’s Hospital. In some cases, undetected liver damage can lead to organ failure and death.

Three years ago, Pollock joined forces with a local Massachusetts biotech company called Diagnostics For All (DFA) to develop a paper-based method for diagnosing liver damage that uses just a droplet of blood. The test was unveiled in September 2012: a square of paper the size of a postage stamp that costs less than $0.10 and measures liver damage with 90 percent accuracy in just 15 minutes (Sci Transl Med, 4:152ra129, 2012). DFA is now analyzing field-test data from 600 patients taking HIV and TB medications in Vietnam, and hopes to apply for regulatory approval in Europe and the United States within the next 1–2 years, says Jason Rolland, senior director of research at the company.

The test has the potential to reduce deaths associated with liver damage in the developing world, and is just one of a handful of new products aimed at bringing affordable, easy-to-use diagnostics to low-resource settings. DFA is using its technology, which takes advantage of the natural wicking ability of paper, to create cheap paper-based assays for preeclampsia and anemia in pregnant women, bacterial contamination of cow’s milk, nutrient deficiency in children, and more—all for pennies per test. Other companies are taking advantage of the near ubiquity of mobile devices, developing a smartphone eye exam, a flashlight that measures diabetes risk, and a tablet app that monitors both heart health and water sanitation.

To increase access to health care in the developing world, “we need a fundamentally different class of diagnostic devices—ones that are robust enough to be used in the field and simple enough to be used by midlevel professionals,” says Sailesh Chutani, president and CEO of Mobisante, a Washington State-based biotech that sells a smartphone-based ultrasound system. “I predict we’ll see more and more of this style of device. It is the only way to get a handle on the global health situation.”

The greatest need

Low-cost, point-of-care diagnostic tests are not new. Today there is a range of simple, rapid HIV assays available, including those that can detect HIV antibodies in whole-blood specimens (no blood processing required), as well as rapid diagnostic tests for malaria that produce results in only 15–20 minutes and require no laboratory or even electricity. In the 10 years since these tests became widely used, they have transformed the management of HIV and malaria worldwide. They have also fueled an industry aimed at making similar low-cost diagnostics for other health burdens in the developing world, including the winner of The Scientist’s 2011 Top 10 Innovations contest—a $10 holographic microscope designed for use in remote locations.

“Not all innovation needs rocket science,” Margaret Chan, director-general of the World Health Organization (WHO), said at the opening session of the 2012 Pacific Health Summit in London. “Given the world’s most pressing health problems, the true genius of innovation these days resides in simplicity.”

GOING DIGITAL: This smartphone ultrasound system is one of a growing number of diagnostic devices that take advantage of near ubiquitous mobile technology.COURTESY OF MOBISANTETraditional tuberculosis testing, for example, includes X-rays and blood tests, both of which are resource and training intensive. The simplest TB diagnostic currently on the market is a sputum smear test, which uses visual detection of TB in a sample of coughed-up mucus. An accurate diagnosis still requires a microscope and trained personnel to identify the bacterium, however. As a result, millions of individuals around the world have undetected, and therefore untreated, TB infections. And the WHO estimates that every untreated individual will spread the bacterium to 10–15 people each year.

Global BioDiagnostics Corp., a Texas-based start-up founded in 2009, is one company pursuing a TB solution, based on research funded by a Bill & Melinda Gates Foundation grant. Recently, Global BioDiagnostics’ founders at Stanford University and Texas A&M Health Science Center demonstrated the ability to detect a minute amount of TB—fewer than 10 bacteria in a sputum sample—using an engineered molecule that fluoresces when cleaved by a TB enzyme called BlaC (Nature Chem, 4:802-09, 2012). Global BioDiagnostics is now moving that proof-of-concept experiment into a full prototype test, which will require “no complex processing steps, no handling or pipetting sputum,” according to President and CEO Michael Norman. A $2,000 fluorescent reader will be required to measure the results, but each TB test is estimated to cost just $5 or less.

Other companies are turning to a new plague of the developing world—chronic diseases. “There is a huge upturn in chronic diseases—epidemics in diabetes, cardiovascular disease, and even cancer—that are now overtaking traditional global health diseases such as malaria,” says Bernhard Weigl, principal investigator at the PATH Center for Point-of-Care Diagnostics for Global Health.

To address this concern, PATH, a nonprofit global health organization that has already developed numerous low-cost diagnostics, is now evaluating two diabetes diagnostics: a quick strip test to diagnose gestational diabetes and a noninvasive diabetes-risk screening procedure. Diagnosing gestational diabetes traditionally requires 8 hours of fasting, a blood draw, and at least two doctor visits for pregnant women. PATH hopes to replace that ordeal with a quick-and-easy strip test that costs less than $3 and requires just a drop of blood. And a second test, under development by Netherlands-based DiagnOptics and New Mexico-based VeraLight, can assess diabetes risk by simply shining a light on a person’s forearm. PATH is currently testing the machine—which records fluorescence emitted from proteins in the skin, indicating the level of sugar in the blood—in clinical trials in India. Weigl hopes the assay will encourage at-risk individuals to take appropriate action to prevent the disease and will cost less than the common diabetes blood test, which runs about $65 per test at a doctor’s office.

“It’s the functional equivalent of a blood-pressure cuff for diabetes,” says Weigl. “Now we can screen large numbers of people relatively cheaply without any invasive procedure.”

There’s an app for that

To keep costs low, some companies are turning to mobile device technology that is becoming ubiquitous the world over. Washington State-based Mobisante, for example, opted to use a smartphone as the backbone for its handheld ultrasound system, which performs scans at a range of frequencies that allows evaluation of many types of tissue. The device, which costs $7,500 including the phone and ultrasound wand, was used in Joplin, Missouri, to help diagnose injuries of the victims of the 2011 tornado and has been used at the Everest Base Camp to screen individuals for pulmonary edema. Last year, the system became the first smartphone-based diagnostic device approved by the US Food and Drug Administration, and the company is currently building partnerships to move it into developing countries, says CEO Chutani.

Another smartphone-based diagnostic that could soon hit the market is a pocket optometrist. Massachusetts-based EyeNetra has developed a $2 plastic lens attachment that snaps onto a smartphone screen and a mobile phone app that gives simple instructions for measuring nearsightedness, farsightedness, and astigmatism. This portable eye exam, which emerged from the Massachusetts Institute of Technology’s Media Lab, could help as many as 2.4 billion people worldwide who need glasses but do not have them, says Vitor Pamplona, cofounder and chief technical officer of EyeNetra.

Also in an effort to keep costs down, diagnostic companies are working to develop tools that can be used directly by patients, bypassing the trip to the doctor’s office. EyeNetra’s device, for example, comes with a simple tutorial and connects to a network service, so that a patient can self-administer the vision test and send results straight to an eyeglass store or ophthalmologist. Similarly, Mobisante’s smartphone ultrasound device connects to wireless networks in order to save images in the cloud and e-mail them directly to a doctor. And DFA hopes its liver toxicity test will someday be a home test, allowing patients to apply a drop of their own blood to the paper diagnostic, snap a picture of it, and send the picture to their physician.

THE DOCTOR IS IN: The Swasthya Slate health tablet provides multiple diagnostics and decision support systems for frontline health workers in India.COURTESY OF UTSAV SHARMAAt the Public Health Foundation of India, health systems engineer Kanav Kahol and colleagues are even hoping that their easy-to-use diagnostic tool, the Swasthya (meaning “health” in Hindi) Slate, will boost the local economy. The Slate is a book-size machine that wirelessly communicates with an Android tablet and includes a bag of plug-and-play sensors that measure blood pressure and levels of blood sugar and hemoglobin, conduct electrocardiography (EKG) tests, and assess water quality. The $350 Slate, including the mobile tablet, is already in use by health-care workers in several southern Indian states. The ultimate goal, says Kahol, is to distribute the device to mobile health assistants, who pay just half the cost while the government picks up the rest of the tab. “Then these guys have a self-employment model, where they can offer these services from home to home for a small fee,” says Kahol.

A worldwide solution

While low-cost diagnostics could revolutionize health care in the developing world, there is one major hurdle to bringing these products to market—money. While the products themselves are cheap, development isn’t. “The problem is almost always funding,” says PATH’s Weigl.

In order to fund a product, some companies look to first sell their device in North America and Europe. The same traits that make a diagnostic appropriate for the developing world—low cost, portability, ease of use— also make it attractive to developed markets. Mobisante, for example, has sold its portable ultrasound device to community clinics and large hospitals in the United States. “Our initial goal was to focus purely on emerging markets. But we realized is that is hard to do, so we found some niches here to get us started,” says Chutani.

EyeNetra also expects to cultivate a market in the developed world. “There is a clear need in the developing world for eye-care diagnostics, but in the developed world, the device also solves a comfort problem for people who don’t want to go to the eye doctor,” notes Pamplona. “We are going to make sure that we target both situations.”

Even a simple technology such as the DFA liver test could be used in developed countries as a way to conserve resources, says Pollock. Of course, “the first priority is the resource-limited setting,” she emphasizes. “We want all people to now have access to the same standard of care as people in a resource-rich setting.”

From The Scientist

The Nano Song with puppets

2012-10-30T11:36:00.003-06:00

Watch this fun video about nano-material/technology. A nano song with puppets dancing and explaining the fundamentals of nano-science. "The Nano Song" is a collaborative effort by a group of researchers from University of California, Berkeley including Patrick Bennett, David Carlton, Molly Felz, Nola Klemfuss, Glory Liu, Ryan Miyakawa, Stacey Wallace, and Angelica Zen, and was the winner of both the Critics' Choice and People's Choice awards.

The Nano Song from nanomonster on Vimeo.

Lab on a Chip: United States of America

2012-09-25T15:00:00.001-06:00

I know it is too long, but it will give you some perspective on lab on chip technology.
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This United States of America themed issue of Lab on a Chip presents an overview of work at the leading edge of microsystems engineering in the USA today. The issue is partly based on work presented in a symposium on ‘‘Microfluidics and Medicine: Accelerating the flow from lab to clinic’’ that was sponsored by the Wyss Institute for Biologically Inspired Engineering at Harvard University and convened in Boston, Massachusetts in May 2011. The focus of this symposium was on research and technology development at the leading edge of the microfluidics field that promises to have a transformative impact on medicine and clinical care. However, this issue covers more ground and includes fundamental articles that describe new microsystem components, fabrication methods and microassays for single molecules, single cells and complex living tissues and embryos, as well as microdevices designed to meet a variety of medical challenges in areas ranging from cancer diagnostics to organ-on-chip replacements for animal testing in drug development.

An Emerging Theme. It is difficult to identify a single, most important theme from a meeting designed to provide a broad overview of advances in a field. Nonetheless, one obvious area of rapid development to emerge from these papers concerns the use of microfluidic systems—in combination with cells—to provide new approaches to the solution of important problems in biomedical analysis. This theme is at least in part an effort to answer a question that has become increasingly important for microfluidics, that is: what does it, uniquely, bring to science and technology? What can microfluidics do, and for which there is a compelling, large-scale application, that no other technique can? The papers, and discussions surrounding them, suggest rapidly growing interest in the ability of microfluidic systems to enable manipulation of mammalian cells in ‘‘life-like’’ circumstances.The growth of this interest in fusing microfluidics with mammalian cell culture—and especially in cell culture involving human cells—has several roots, of which two are based in the pharmaceutical industry. i) Decreasing the probability of failure of drug candidates in clinical trials. The pharmaceutical industry, globally, has (to express the problem in an understated way) encountered ‘‘growing difficulties’’ in evaluating toxicity and efficacy using its present techniques. A part of the difficulty—and perhaps much of it—has to do with the very incompletely understood differences between humans and animal models for humans (mice, rats, dogs, pigs, and so on). A human patient is not a large mouse, and drugs that seem to be safe and effective in animals are not necessarily equally so in humans. By this analysis, expanded testing of drug candidates for intended use in humans, using human cells and tissues—although also certainly not able to predict outcomes completely in intact humans, and certainly not to predict outcome across the broad phenotypic and genetic range of humans—would provide one additional and particularly relevant type of information to use in selecting against compounds that are likely to fail in human clinical trials.Microfluidic systems of some design will probably be required for these types of studies, since primary human cells will always be expensive and in short supply, and since certain processes important in tissues (for example, ensuring that delivery of nutrients from medium to the cells is not limited by mass transport) require small systems. ii) Patient-specific Medicine. A second, growing awareness in the pharmaceutical industry is that the range of human response to xenobiotics can be very broad, and developing economical, timely ways of testing the response of individual humans, or members of particular genetic subpopulations, to pharmaceuticals has the potential to increase the safety and efficacy of drugs. This type of bioassay will, again, often require microfluidic systems, since tissue samples willfrequently—if not always—be small: the tissue available from a needle biopsy of a tumor or from circulating tumor cells isolated from a patient’s blood are simple examples.

The blending of microfluidic systems, cell biology, tissue engineering and organ physiology suggests a new direction for microfluidic technology: away from complex systems of valves, channels, and microscale incubation chambers, and toward systems of sufficient simplicity to be useable with the great technical complexity required to grow, dose, and analyze cells and tissues. Microfluidics (as a field, and by the nature of the individuals who have worked in it) has tended, implicitly, to model itself on integrated circuits, and to assume that ‘‘more complexity is more capability.’’ In fact, the right model may be the opposite: ‘‘The simpler (when combined with complex biology) the better.’’ A movement toward simplicity of microsystem design and compatibility with complex biology would be a new one for the field: that is, toward technology guided by biomedical science, rather than technology grown from physical science.At the same time, as microengineers find themselves selecting living cells as system components, they need to learn the design principles that govern how cells become organized and function within living tissues, as well as how tissues join together to form functional organs. Combination of different types of cells and linkage of different tissues and micro-organs to study whole organism physiology will require new types of pumps, channels and sensors—ones that are designed with physiological relevance and simplicity of operation constantly in mind. In addition to maintaining cell viability and permitting real-time analysis of mammalian cells, another important advantage of microsystems engineering is that our methods enable us to fabricate microdevices with precise geometry, topography, mechanics, chemistry and flow dynamics on the same scale as that which determines cell organization with living tissues. Recentadvances in using microtechnologies to build organ-on-chip microsystems that reconstitute tissue–tissue interfaces and to recapitulate organ-level functions in vitro demonstrate the potential value that this approach offers as an alternative to conventional cell-based systems for validation of drug candidates, as well as for toxicity screening of chemicals, cosmetics and toxins.

The final issue that was addressed in the meeting, and in this issue, centers on the many obstacles that still need to be overcome when it comes to translation and commercialization of microfluidics technologies for high-value medical applications. When it comes to commercializing a microsystems technology, the reality in the trenches is far worse than what we see from our optimistic perspectives at the lab bench at universities and research institutes around the world. As researchers, we strive to push the envelope, to incorporate as many ‘bells and whistles’ as possible, and, very simply, to impress, without regard to materials, robustness, scale-up or cost.When trying to commercialize a technology, the major technical focus is on rigidifying the design, selecting cost-effective materials optimized for the specific application, finalizing processes and procedures, and developing scalable manufacturing— basically, this represents starting from scratch. More importantly, technical advances are meaningless if they are not driven by a commercialization plan led by an entrepreneur who is focused on a single, high value application that is best suited to the technology at hand. In the past, academics worked at the bench in isolation, and hoped that someday if technical success was demonstrated, an entrepreneur or corporate partner would drop from the sky and make their vision into a reality. This model has not worked. It’s time for all of us to think of the long-term challenges that must be overcome for our inventions to have an impact on the world, and to redesign how we carry out research at the bench to ensure that these microtechnologies take the shortest path to success.

Donald E. Ingber and George M. Whitesides

Lab on a Chip EDITORIAL, 2012
http://gmwgroup.harvard.edu/pubs/pdf/1148.pdf

Paper Devices research Moving Forward

2012-08-20T17:33:00.000-06:00

University of Notre Dame chemistry professor Marya Lieberman and graduate student Abigail Weaver spent a week in June in Eldoret, Kenya, going from office to office in a regional hospital meeting people involved with pharmaceutical purchasing.

In hospitals like the one they visited, vigilant purchasing agents have to be on the lookout for counterfeit pharmaceuticals, but they often lack appropriate equipment to assess drug authenticity. Lieberman and Weaver develop paper-based microfluidic devices that can do such tests.

Hospitals like the one in Kenya “don’t have lab space,” Lieberman says. “There’s not even space to set up a suitcase lab.” In that type of environment, paper-based instruments can come in very handy. “We would whip out our paper devices and do tests right there on their desktops,” she says.

Lieberman ticks off the reasons people want to use paper devices. “They’re cheap, transportable, disposable, cheap.” She pauses for a beat. “Have I mentioned that they’re cheap?”

Lieberman is just one of a growing number of scientists who are turning to paper as a platform for microfluidic analytical devices. She and others were attracted to the field after reading George H. Whitesides’ first paper on the topic, published inAngewandte Chemie in 2007 (DOI: 10.1002/anie.200603817).

A varied cast of scientists is pushing the field forward, some by developing and improving paper-based microfluidic devices and others by using the devices for specific assays. The desire to run point-of-care medical diagnostic tests in limited-resource settings drives much of the work in this area.

For example, Paul Yager, a bioengineering professor at the University of Washington, Seattle, was already trying to develop low-cost diagnostics when he heard about paper-based devices. At the time, he was working on a project funded by the Gates Foundation to develop permanent instruments with disposable cartridges. The Bill & Melinda Gates Foundation would fly its grant recipients to annual meetings in locations where such devices might actually be used.

“They would take us out to real situations, real clinics, real population centers in the developing world—places that I frankly hadn’t been to before,” Yager says. “You’d get to chat about things like their actual budgets and the real issues and the most pressing problems. After five years of exposure to that, I reached the conclusion that the cost per test had to be way, way down, below what I still think the cost per test is going to be with the kind of technology that was being developed with a permanent instrument.”

But cost was only part of the problem, Yager adds. “Permanent instruments are a pain to use in the developing world. If you’re lucky, they sit someplace and stay plugged in. If you’re not lucky, they break or wander off, and you lose your ability to run them. It’s not easy to get a service call and, depending on where you are, not all that easy” to pack an instrument and have a shipper like FedEx pick it up for off-site servicing.

With paper-based devices, such worries disappear. Paper-based devices often don’t require power supplies. Many of them can be read by eye or with a camera phone—a common tool in the developing world.

Lieberman’s group and teams at other academic institutions with which they collaborate—led by Patrick J. Flynn and Holly V. Goodson from the University of Notre Dame and Toni L. O. Barstis from Saint Mary’s College, in Notre Dame, Ind.—develop chemical tests for counterfeit pharmaceuticals.

“We’re trying to put together libraries of color tests and get them all to play nicely with each other,” Lieberman says. “We’re also making a smart material, where information on how to add the reagents is stored in the paper matrix and the test output can be read like a color bar code.”

For pharmaceutical identification, each device has several lanes that detect certain functional groups, such as primary amines or phenols, in an active pharmaceutical ingredient. Lieberman also looks for approved or unauthorized excipients (inert ingredients). Color changes in the various lanes indicate the presence of particular components.

“These are chemical tests, so you have to be careful in interpreting them,” she says, noting that the tests are not yet sufficiently quantitative. The main bar to quantitation has been the difficulty of developing a reliable method of dosing. For ease of use, “we made a decision not to grind up tablets and make volumetric solutions,” Lieberman says. Instead, she and her coworkers simply swipe pills across the graterlike sampling region of the device.

They are working on the grater to make the device more quantitative. Nonetheless, the device is quantitative enough that during a workshop in Kenya it was able to reliably distinguish pure amoxicillin from amoxicillin that had been cut 50/50 with maize meal.

The current iteration of the test has 12 lanes, a sufficient number to identify the four frontline tuberculosis medications individually or in combination tablets of two or four drugs. The 12 lanes can be used to detect all four drugs individually, all seven possible binary combinations, and the quaternary combination.

In the medical diagnostics area, a device to perform liver function tests from the nonprofit corporation Diagnostics for All (DFA), based in Cambridge, Mass., is closer than any other paper-based device to working in the real world. The company holds an exclusive license to a number of patents from the Whitesides lab.

The test measures the levels of two liver enzymes—aspartate aminotransferase and alanine aminotransferase—and provides a colorimetric readout, says Una Ryan, DFA’s chief executive officer. By comparing the readout with a color guide, medical personnel can categorize the test results as normal, worrisome, or requiring immediate action.

DFA’s contribution has been to take academic ideas and turn them into real products, Ryan says. Most important, she adds, is that the tests are reliable and reproducible.

“It doesn’t matter how cheap something is. People won’t use it if it’s not reliable,” she says. “In the developing world, people don’t use diagnostics more often because they’re too expensive and not reliable.”

The devices currently made by DFA are stable for at least a year in high-temperature, high-humidity environments, Ryan says. The devices are now being tested at a Harvard University-affiliated AIDS hospital in Ho Chi Minh City, Vietnam. The hospital has a high incidence of hepatitis as well as AIDS, meaning that there is a substantial patient population with compromised liver function, making it possible to study whether the device measures what it’s supposed to measure. A 700-patient trial is ongoing.

DFA has developed a semiautomated process for manufacturing the devices, but the biggest hurdle to widespread use is what Ryan calls “the last mile”—distribution. Organizations like DFA can work easily with national or regional governments, but getting devices to people who work in rural communities “requires a lot of skill and good relationships,” she says.

DFA’s liver function test has not yet received regulatory approval. Most countries in the regions DFA is targeting accept both U.S. and European regulatory approvals. DFA will first apply for the CE mark, which denotes compliance with European regulatory standards. After that, it might also seek approval through the U.S. Food & Drug Administration’s 510(k) regulatory process for medical devices.

A growing number of academic researchers are working on ways to extend the capabilities and improve the assembly of paper devices. For instance, Scott T. Phillips and coworkers at Pennsylvania State University have incorporated fluidic batteries directly into paper-based microfluidic devices (Lab Chip, DOI: 10.1039/c2lc40126f).

In many conventional detection methods, like fluorescence assays, you need a source of power, Phillips says. “In really resource-limited environments, button batteries may be too expensive or have disposal hazards. We’re asking the question: Can we generate the power directly” in a paper-based device?

Phillips and his coworkers are helping answer this question by making multilayer batteries with electrolytes, electrodes, salt bridges, and conductive connections. Using AgNO₃ and AlCl₃ electrolytes, they constructed galvanic cells that can be connected in series or parallel and that produce enough current to power a light-emitting diode.

Phillips’ group recently devised a way to simplify the assembly of multilayer paper-based devices. Rather than alternate paper and tape layers, as is commonly done in the construction of such devices, Phillips and coworkers use spray adhesive to stick the layers together (Lab Chip, DOI: 10.1039/c2lc40331e). “The quantity of glue we are using to put two pieces of paper together is sufficiently small that it doesn’t seem to affect the wicking or wetting properties of the paper,” Phillips says. And the process is rapid enough that a single researcher can assemble hundreds of devices within an hour, he says.

Another group uses origami—Japanese paper folding—to craft multilayer paper-based devices from single pieces of paper. When Hong Liu, a graduate student in Richard M. Crooks’s group at the University of Texas, Austin, who grew up in China, first saw multilayer paper-based devices, they reminded him of origami objects he had assembled in childhood art classes.

Crooks’s group incorporates electrochemical detection into its devices by screen-printing electrodes on single pieces of paper and then using origami to fold them into multilayer operational units. Current devices have carbon electrodes, but he and his coworkers are developing devices with gold electrodes to make it easier to immobilize probe molecules on the devices.

They plan to use the origami devices for assays that test immunization status—for example, to identify children who have been immunized, even if their immunization card has been lost.

[+]Enlarge

LIVER TEST

These paper devices measure levels of the liver enzymes aspartate aminotransferase and alanine aminotransferase as well as positive and negative controls. Each device is 1 square inch.

Credit: Diagnostics For All

Not everybody wants to use multiple layers of paper in their paper-based device. Yager is trying to develop devices that perform multistep reactions using single pieces of paper. “I’m a monopapyrist,” he says. “I’d like all my devices to have one continuous strip of paper, no matter what the shape is.”

The challenge with using only one piece of paper is how to get all the reagents to the right place at the right time. Control of fluid flow is a critical part of that process. In conventional microfluidic devices, pumps control fluid flow. With paper, the fluid naturally wicks through the device. “One of the great things about paper is you get to throw away the pumps,” Yager says. But “the paper material has to be very uniform to do the kinds of things we’re trying to do. We’re trying to program fluid flow rates and arrival times using paper.”

The goal of all that flow control is getting the sample and reagents to a desired spot on a device. “Everything ultimately has to come to the place where I’ll make a measurement,” Yager says. “The whole question is how do I get that spot to change in a pattern and intensity that relates to how much stuff was there.”

Yager and coworkers recently used two-dimensional paper networks to detect a malaria antigen (Anal. Chem., DOI:10.1021/ac300689s). And they are currently working on an isothermal method for nucleic acid amplification on a paper device. To design such devices, they first figure out how to make each individual step work on separate pieces of paper and then connect those “subroutines” on a single piece of paper. “We’ve developed a tool kit of paper processes,” he says.

Many paper devices are laminated, both to hold them together and to keep out contaminants. But lamination can require extra steps to incorporate sample inlets. Andres W. Martinez and coworkers at California Polytechnic State University, San Luis Obispo, have developed a way to use printing instead of lamination to enclose and protect devices (Anal. Chem., DOI:10.1021/ac202837s).

They pattern channels on paper devices using a wax printer, add any reagents needed for the assay, and then run the paper through a standard laser printer. The toner, which is thermally bonded to the paper, encloses and protects the resulting device, making it easier to handle and operate.

Martinez’ experiments suggest that the toner coating is gas permeable, with some water vapor escaping. However, liquid water doesn’t permeate barriers consisting of at least four layers of toner. Martinez believes the toner-sealing method’s optimal use will not be more large-scale manufacturing but instead allowing small labs to carry out rapid prototyping of paper-based devices.

Most specialists of paper-based devices are working on medical tests, and initially Charles Henry, a chemistry professor at Colorado State University, was no exception. In collaboration with researchers at Chulalongkorn University, in Bangkok, he developed a paper device for metabolic disease detection that used electrochemical detection instead of the colorimetric methods favored by most people. Now Henry is instead developing paper-based exposure monitors for occupational health applications.

Among the devices his group has designed are paper-based systems that measure oxidative stress caused by atmospheric aerosols. During this summer’s Colorado wildfires, firefighters wore such paper devices to measure their exposure to oxidative stress from the fires.

His group has also developed paper devices to measure metal particles in occupational settings. The researchers collect metals on filters, punch out disks from the filters, and put those disks on paper devices where the metals are digested with acid and transported to detection reservoirs by the addition of water. The reservoirs contain reagents needed for the colorimetric detection of various metals.

Detection sensitivity has been a challenge, Henry says. In early experiments, an iron-phenanthroline complex formed in the test would develop a ring around the outer edge of the detection reservoir. “We always saw the same color,” Henry says, making it impossible to distinguish different amounts of metal particles. He and his coworkers have dealt with such problems by modifying the paper to make the tests more discriminating.

The number of potential applications of paper-based devices is growing. “I think of this as the next frontier of microfluidics,” Henry says. “When people started off in microfluidics, they said, ‘Here are 10 things you can do with it.’ Those 10 things became 100, and it really grew from there. The same thing is true of paper devices. More and more people are going to see unique applications. The field will continue to grow until it fills underserved niches as an analytical tool or a medical tool.”

Anal Chem Young Innovator Award 2012 to Microfluidic/nanofluidic Prof Herr

2012-07-12T17:33:00.001-06:00

Prof. Amy E. Herr of the UC, Berkeley is the recipient of the Analytical Chemistry 2012 Young Innovator Award. This award is sponsored by Analytical Chemistry and the Chemical and Biological Microsystems Society (CBMS). It recognizes the contributions of an individual who has demonstrated "exceptional technical advancement and innovation in the field of micro- or nanofluidics in his or her early career".

Past Recipients:

2011, Aaron Wheeler, University of Toronto
2010, Daniel Chiu, University of Washington (UW)
2009, Jongyoon Han, Massachusetts Institute of Technology (MIT)
2008, Joel Voldman, Massachusetts Institute of Technology (MIT)

Microfluidics for STD diagnostics in the developing world #SamualSia

2012-05-29T19:37:00.001-06:00

Dr. Samuel Sia, Professor of Biomedical Engineering at Columbia University, talking on poin of care diagnostic devices for detecting disease markers during Cla2010 Conference on Global Health Diagnostics "GHDx Innovations Summit: Translating Ideas into Impact".

Point-of-Care Diagnostics for the Developed and Developing World #paper microfluidics

2012-05-14T15:56:00.000-06:00

In this video, Paul Yager, Professor of Bioengineering, University of Washington talks about the paper based diagnostic devices for different types of assays. These devices are cheap, easy to fabricate, don't require instrumentation, very useful in developing world.

Instruments/equipments in a microfluidic laboratory

2012-05-08T09:38:00.000-06:00

I am presenting the instruments/facilities that we use in our microfluidic/nanofluidics instrumentation laboratory. We primarily fabricate glass based microfluidic devices ourselves and use them for different biological applications.

1. We have a basic photolithography setup that includes a dark room, UV light source and developing solution.

2. Then we perform wet chemical etching to make channel networks on the substrate glass plate using BOE (buffered oxide etchant) which is an appropriate mixture of HF and NH4F.

Chemical wet etching setup

The BOE solution is heated to certain temp to fasten the etching rate and stirred continuously to have uniform etching. The solution on the right is Chromium etchant which removes chromium layer from the substrate plate.

3. Sand blaster is used to make holes to have access to the channels. It uses 25-50 micron sand particles which are bombarded on the surface of glass substrate. It makes holes of ~1mm diameter.

Sand blaster to make holes

4. This small microscope is sometimes used to visualize the channels during chip fabrication process.

Microscope

5. Ovens: We have two ovens. Both of them are used for drying purpose and for high temperature bonding of glass plates (right one).

6. Refrigerators: We have two refrigerators. One shown below is set for 4 deg C and also has a -20 deg C freezer. We use this for storing our biological samples (proteins, reagents). The other one (not shown here) maintains a temp of -76 deg C. This is used to use those samples which require very low temp.

7. Centrifuge, UV lamp, and sonicator

8. Profiler: This is used to measure the depth of micro/nano channels. It measure upto nanometer level.

9. Fluorescence microscopes: We have four fluorescence microscopes. They are equipped with highly sensitive camera or PMT detectors. Using these microscope we study different phenomena occurring inside microchannels. These microscopes are also equipped with high voltage power supply devices.

10. Metal evaporator: We use this device to make electrodes in the microcip. It evaporates metal (we use chromium and gold, regularly) on the chip surface in a vacuum chamber.

11. Black boxes: We have four of such black boxes which have laser induced fluorescence, high voltage power supply and are controlled using PC.

-Basant

www.bgiri.com

Simple Blood Typing in Paper device

2012-05-01T09:36:00.000-06:00

For anyone who has ever wondered what their blood type is, a new paper-based device will literally write the answer, providing an inexpensive and unambiguous way to determine blood type (Angew. Chem. Int. Ed., DOI:10.1002/anie.201201822).

The presence or absence of certain antigens on red blood cells determines a person’s blood type. Specific antibodies will react with these antigens and make the red blood cells clump. Researchers led by Wei Shen, of Australia’s Monash University, use an ink-jet printer to apply these antibodies in the shapes of letters A, B, and X as well as a vertical line onto postage-stamp-sized pieces of paper towel. O and rhesus-negative blood types don’t have antigens that react with these antibodies, so the researchers preprint an O in the same spot as the X and a horizontal line intersecting the vertical line on the paper in red waterproof ink.

Place a few drops of blood on the paper, wash it with saline, and in under a minute,the blood type appears in text. For example, if the blood type is A-positive, antigens will react with printed A antibody to produce a clump of red blood cells in the shape of the letter A and with antibody in the vertical line to form a + sign. The antigens will also cause a red X to form over the preprinted O. For O-negative blood, no reaction with the antibodies would occur, and the preprinted paper would simply read O above a – sign.

Shen got the idea after seeing the film adaptation of J. K. Rowling’s book “Harry Potter and the Chamber of Secrets,” in which the characters query a diary that responds in writing. Shen realized technology he had previously helped develop could be modified to respond in writing to the question: What’s my blood type?

“The ability to form letters that directly report blood type makes it possible for nonexperts to interpret the results rapidly, which is of particular importance in rapid-response scenarios,” comments John D. Brennan, an expert in bioanalytical chemistry at McMaster University in Ontario. “This method also shows the advantage of implementing simple ink-jet printers to produce paper assays rather than conventional lateral flow printers, which produce only lines.”

Scanning Electron Microscope Videos: Learn SEM

2011-12-20T17:33:00.000-07:00

The scanning electron microscope is used to image the surface of a conducting sample by scanning it with a high energy beam of electrons. Some SEMs have additional software enhancements than enable them to focus the beam on a photomask for E-beam lithography or are equipped for focused ion beam (FIB) milling.

Microfluidics and nanofluidics have lots of applications that require SEM. This post contains a good collection of videos explaining basics of SEM and how to use the instrument.

There are total of six videos.

Part 1.

Part 2.

Part 3.

Part 4.

Part 5.

Part 6.

Laminar Flow in Paper Microfluidics

2011-07-20T17:33:00.000-06:00

These days I am more into paper microfluidics. I am hoping to work on these devices in future. These devices will have more values in developing countries which lack resources. Here, I post a video from youtube. The video shows a controlled flow of reagent in 2D paper networks.