| Abstract
| - Digital microfluidics is a fluid manipulation technique inwhich discrete droplets are actuated on patterned arraysof electrodes. Although there is great enthusiasm for theapplication of this technique to chemical and biologicalassays, development has been hindered by the requirement of clean room fabrication facilities. Here, we presenta new fabrication scheme, relying on microcontact printing(μCP), an inexpensive technique that does not requireclean room facilities. In μCP, an elastomeric poly(dimethylsiloxane) stamp is used to deposit patterns of self-assembled monolayers onto a substrate. We report threedifferent μCP-based fabrication techniques: (1) selectiveetching of gold-on-glass substrates; (2) direct printing ofa suspension of palladium colloids; and (3) indirecttrapping of gold colloids from suspension. In method 1,etched gold electrodes are used for droplet actuation; inmethods 2 and 3, colloid patterns are used to seedelectroless deposition of copper. We demonstrate, for thefirst time, that digital microfluidic devices can be formedby μCP and are capable of the full range of digitalmicrofluidics operations: dispensing, merging, motion,and splitting. Devices formed by the most robust of thenew techniques were comparable in performance todevices formed by conventional methods, at a fraction ofthe fabrication time. These new techniques for digitalmicrofluidics device fabrication have the potential tofacilitate expansion of this technology to any researchgroup, even those without access to conventional microfabrication tools and facilities.
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