Bonding of Polydimethylsiloxane Microfluidics to Silicon-Based Sensors

We investigate bonding polydimethylsiloxane (PDMS) to silicon using a thin (∼2 μm) intermediate adhesive layer stamped onto a PDMS piece prior to bonding. In particular, we compare as adhesive layers Sylgard 184 and 182 curing agents and a UV curable adhesive (NOA 75). We examine the effect of both curing temperature and duration on curing agent bond strength. Bond strengths for the different adhesives are determined by measuring the average burst pressure at a PDMS-silicon interface using a PDMS test design. We find that Sylgard 184 curing agent gives the highest bond strength with burst pressure of 700 kPa or more for curing at either 60°C for 3 h, 70°C for 30 min, or 90°C for 20 min. Curing at room temperature takes substantially more time with an average burst pressure of 433 and 555 kPa for curing times of 16 and 27 h, respectively. In comparison, Sylgard 182 curing agent takes 32 h at room temperature to achieve a burst pressure of 289 kPa, while NOA 75 with a 50°C 12 h post-UV exposure bake yields a burst pressure of 125 kPa.