Electroosmotic properties of microfluidic channels composed of poly(dimethylsiloxane)

Microfluidic devices fabricated from polymers exhibit great potential in bi ological analyses. Poly(dimethylsiloxane) (PDMS) has shown promise as a sub strate for rapid prototyping of devices. Despite this, disagreement exists in the literature as to the ability of PDMS to support electroosmotic (EO) flow and the stability of that flow over time. We demonstrate that in low i onic strength solutions near neutral in pH, oxidized PDMS had a four-fold g reater EO mobility (mu (eo)) compared to native PDMS. The greater mu (eo) w as maintained irrespective of whether glass or PDMS was used as a support f orming one side of the channel, This enhanced mu (eo) was preserved as long as the channels were filled with an aqueous solution. Upon exposure of the channels to air, the mobility decreased by a factor of two with a half-lif e of 9 h. The EO properties of the air-exposed, oxidized PDMS were regenera ted by exposure to strong base. High ionic strength, neutral in pH buffers compatible with living eukaryotic cells diminished the EO flow in the oxidi zed PDMS devices to a much greater extent than in the native PDMS devices. For analyses utilizing intact and living cells, oxidation of PDMS may not b e an effective strategy to substantially increase the mu (eo). (C) 2001 Els evier Science B.V. All rights reserved.