Rapid Prototyping of Microfluidic Systems in Poly(dimethylsiloxane)

TLDR

This paper presents a rapid (<24 h) procedure for designing and fabricating microfluidic systems in PDMS. The method uses a CAD‑designed channel layout printed as a high‑resolution transparency mask for photolithographic master fabrication, PDMS casting, oxygen‑plasma oxidation of both the replica and a flat slab, and subsequent irreversible bonding to create sealed devices. Oxidized PDMS surfaces bond irreversibly to each other and to common substrates, produce negatively charged channels that support electroosmotic pumping, and enable capillary‑electrophoresis separations with resolution comparable to fused‑silica capillaries.

Abstract

This paper describes a procedure that makes it possible to design and fabricate (including sealing) microfluidic systems in an elastomeric material [Formula: see text] poly(dimethylsiloxane) (PDMS) [Formula: see text] in less than 24 h. A network of microfluidic channels (with width >20 μm) is designed in a CAD program. This design is converted into a transparency by a high-resolution printer; this transparency is used as a mask in photolithography to create a master in positive relief photoresist. PDMS cast against the master yields a polymeric replica containing a network of channels. The surface of this replica, and that of a flat slab of PDMS, are oxidized in an oxygen plasma. These oxidized surfaces seal tightly and irreversibly when brought into conformal contact. Oxidized PDMS also seals irreversibly to other materials used in microfluidic systems, such as glass, silicon, silicon oxide, and oxidized polystyrene; a number of substrates for devices are, therefore, practical options. Oxidation of the PDMS has the additional advantage that it yields channels whose walls are negatively charged when in contact with neutral and basic aqueous solutions; these channels support electroosmotic pumping and can be filled easily with liquids with high surface energies (especially water). The performance of microfluidic systems prepared using this rapid prototyping technique has been evaluated by fabricating a miniaturized capillary electrophoresis system. Amino acids, charge ladders of positively and negatively charged proteins, and DNA fragments were separated in aqueous solutions with this system with resolution comparable to that obtained using fused silica capillaries.