A long-term, stable hydrophilic poly(dimethylsiloxane) coating for capillary-based pumping

Hydrophilic surfaces are highly desirable for transporting liquids within microchannels. However, creating stable hydrophilic surfaces on poly(dimethylsiloxane) (PDMS) is a challenging feat. We present a straightforward method for generating stable hydrophilic coatings in which poly(ethylene glycol) (PEG) is bonded to PDMS through a 3-step fabrication process. The resulting surfaces are rendered hydrophilic having a contact angle of 17° ± 2°. Additionally, this coating exhibits long-term stability maintaining a contact angle <22° for at least 47 days. Various PEG-coated PDMS microchannels were fabricated for flow characterization studies and for demonstrating the effectiveness of this technique for on-chip fluidic processing.