Pluronics f 127 solution

To generate a PDMS basal membrane, PDMS prepolymer was spin-coated onto 100 mm petri dish covers at 500 rpm for 30 sec followed by curing at 70°C for 40 hr. The resultant PDMS basal membrane had a thickness of 200 – 300 μm. In parallel, the thin PDMS layer holding the PDMS micropost array was gently peeled off from the coverslip, flipped, and brought into conformal contact with a PDMS pad before the backside of the PDMS layer was treated with air plasma. The thin PDMS layer holding the PDMS micropost array was then bonded to the PDMS basal membrane via plasma-assisted PDMS-PDMS bonding to generate the final SμPA. The SμPA was submerged sequentially in 100% ethanol (10 sec), 70% ethanol (10 sec), 30% ethanol (10 sec), DI water (10 sec), and 0.2% w/v Pluronics® F-127 solution (Sigma-Aldrich; 1 hr), before rinsed three times with DI water. Functionalized SμPA could be stored in phosphate-buffered saline (PBS; Invitrogen) solution for up to one week before use.