Fabrication, derivatization, and applications of plastic microfluidic devices

Abstract

Control of the polymer surface chemistry is a crucial aspect in the development of plastic microfluidic devices. When commercially available plastic substrates are used to fabricate microchannels, differences in the electroosmotic flow (EOF) from plastic to plastic can be very high. Therefore, we have used polyelectrolyte multilayers (PEMs) to alter the surface of microchannels fabricated in plastics. The PEMs are easily fabricated and provide a means for controlling the flow direction and the electroosmotic mobility in the channels. Optimal modification of the microchannel surfaces was obtained by coating the channels with alternating layers of poly(allylamine hydrochloride) and poly(styrene sulfonate). The efficacy of the surface modification has been evaluated by measuring the electroosmotic flow mobility. When microchannels prepared in different polymer substrates were modified with PEMs, they demonstrated very similar electroosmotic mobilities. The PEMs have also been used to immobilize chemically selective molecules in the microchannels. In addition, relatively complex flow patterns, with simple arrangements of applied voltages, have been realized by derivatization of different arms of a single device with oppositely charged polyelectrolytes. Flow in opposite directions in the same channel is also possible; a positively derivatized plastic substrate with a negatively charged lid was used to achieve topbottom opposite flows.