Fabrication of Paper-Based Fluidic Devices (microPADs)  
A simple microPAD patterned by wax printing

MicroPADs (short for microfluidic paper-based analytical device) are a relatively new class of fluidic devices made out of paper patterned into hydrophilic channels, which wick fluids, bounded by hydrophobic barriers, which contain the fluids within the channels. Dr. Martinez fabricated the world's first microPAD in 2006, while pursuing his PhD under the direction of George Whitesides at Harvard University. MicroPADs have since gained wide attention for applications in point-of-care diagnostic devices for use in resource-limited settings (i.e., remote areas with no electricity, running water or trained medical personnel). The technology for fabricating microPADs is constantly evolving, and we continually work to improve our fabrication techniques in order to simplify the fabrication process and add capabilities to the devices. Our group's first project focused on the fabrication of fully-enclosed microPADs by printing a layer of toner on the top and bottom of the devices using a laser printer. The toner protects the channels from contamination, increases the wicking rates of the channels and facilitates operation of the device. You can find our current methods under "Methods."

Paper-Based Diagnotic Devices  

A fully enclosed microPAD after detecting glucose (center) and alkaline phosphatase (right). The test zone on the left was a negative control.

The primary application of microPADs is as platforms for low-cost point-of-care diagnostic devices. We work on integrating known colorimetric assays with our devices and optimizing the performance of the assay on the paper-based platform. We are also developing one-step immunoassays that can be performed on cellulose instead of nitrocellulose.

MicroPADs as Tools for Research and Teaching  
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Aside from being useful as point-of-care diagnostic devices, microPADs are excellent tools for basic reasearch and for teaching. The low-cost and low reagent requirements of microPADs makes them well-suited for use in laboratory classrooms and in research laboratories where cost may be a major consideration. We are developing experiments for an undergradate curriculum, which will expose students to common techinques, such as ELISA, in addition to fabrication of the devices.

Sythesis of Uremic Toxins (p-cresyl sulfate)  
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We are collaborating with Professor Timothy Meyer at Stanford University on this project. We syntehsize sulfated uremic toxins, these are toxic compounds that accumulate in patients with kidney failure, and send the material to the Meyer lab to be used as reference material for calibrating their measurments of these compounds in human samples and also for performing in vitro experiments to model the clearance of these compounds by dialysis.


© 2012 A. W. Martinez. All rights reserved