On-ratio PDMS bonding for multilayer microfluidic device fabrication

Integrated elastomeric valves, also referred to as Quake valves, enable precise control and manipulation of fluid within microfluidic devices. Fabrication of such valves requires bonding of multiple layers of the silicone polymer polydimethylsiloxane (PDMS). The conventional method for PDMS-PDMS bonding is to use varied ratios of base to crosslinking agent between layers, typically 20:1 and 5:1. This bonding technique, known as 'off-ratio bonding', provides strong, effective PDMS-PDMS bonding for multi-layer soft-lithography, but it can yield adverse PDMS material properties and can be wasteful of PDMS. Here we demonstrate the effectiveness of 'on-ratio' PDMS bonding, in which both layers use a 10:1 base-to-crosslinker ratio, for multilayer soft lithography. We show the efficacy of this technique among common variants of PDMS: Sylgard 184, RTV 615, and Sylgard 182.