Integrated Elastomer Fluidic Lab-on-a-chip –
Surface Patterning and DNA Diagnostics
, Marc A. Unger
, Axel Scherer
, and Stephen R. Quake
Departments of Electrical Engineering
and Applied Physics
Pasadena, CA 91125, USA
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.
circulations are also demonstrated.
Several techniques are currently being developed towards the
goal of an integrated fluidic lab-on-a-chip
. Among these,
monolithic microvalves and micropumps made from silicone
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
. The sensitivity of such arrays is limited in
part by the diffusion of target DNA to the probes that are anchored
on the surface
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.
technological advances in the current state of the art of
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
The first two issues we have addressed by using "soft