hiltonh00 - Integrated Elastomer Fluidic Lab-on-a-chip...

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Integrated Elastomer Fluidic Lab-on-a-chip – Surface Patterning and DNA Diagnostics Hou-Pu Chou * , Marc A. Unger + , Axel Scherer *+ , and Stephen R. Quake + Departments of Electrical Engineering * and Applied Physics + , Caltech, Pasadena, CA 91125, USA ABSTRACT We recently developed a method of multilayer fabrication for elastomeric devices, which we used to fabricate monolithic active valves and pumps. Here we describe efforts to use these pumps and valves in an integrated DNA diagnostic chip and show results of a key component, surface patterning, with two different kind of surface chemistries by using similar elastomeric channel devices. Flow control, reagent metering, in-line mixing and loop circulations are also demonstrated. INTRODUCTION Several techniques are currently being developed towards the goal of an integrated fluidic lab-on-a-chip [1-6] . Among these, monolithic microvalves and micropumps made from silicone elastomer [5] have great potential because of their simplicity, robustness, easy fabrication and low cost. Here, we describe some new results and extensions to our previous work as part of our ultimate goal of creating an integrated DNA diagnostic chip. We are interested in using microfabricated chips to measure gene expression and detect the presence of pathogenic DNA. DNA expression arrays have proved to be a useful tool in studying gene expression in a variety of organisms, including yeast, worm, mouse and human [7] . The sensitivity of such arrays is limited in part by the diffusion of target DNA to the probes that are anchored on the surface [8] . A better approach is to use microfluidic devices in order to pump solutions of target DNA over a set of anchored probes in order to ensure that all of the target DNA is exposed to each of the probes. This would provide increased sensitivity as well as decreasing the amount of time needed for hybridization. Chips with high sensitivity would also be useful for measuring single cell gene expression. This higher sensitivity may eliminate the need for PCR in many cases of pathogen detection and therefore make it possible to do multiple disease diagnosis with one integrated lab-on-a-chip. Making such chips requires a number of important technological advances in the current state of the art of microfluidics. First, one needs to be able to fabricate microfluidic devices in a way that is compatible with the delicate surface chemistry required to anchor or synthesize DNA probes on a chip. Second, one must be able to effect the desired patterning or surface chemistry. Third, one must be able to manipulate small amounts of material and perform the necessary biochemical reactions on chip. Finally, one needs to be able to pump the targets over the probes. The first two issues we have addressed by using "soft
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hiltonh00 - Integrated Elastomer Fluidic Lab-on-a-chip...

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