Microfluidic designs were sent to a cleanroom for master mold fabrication (Stanford Microfluidics Foundry, Stanford, California). Mold fabrication was done using standard SU-8 photolithography.17,18,20 Upon obtaining the mold, microfluidic chambers were cast using Sylgard 184 silicone. First, 100 g of Sylgard 184 silicone elastomeric base was mixed with 10 g of Sylgard 184 silicone elastomeric curing agent (Dow Corning, Midland, Michigan). The mixture was then placed into a vacuum desiccator to remove air bubbles. In a different vacuum desiccator, 2 mL of trichloromethylsilane was evaporated onto the master mold wafers for 20 min (Sigma-Aldrich, Saint Louis, Missouri). The elastomer mixture was poured onto the mold and left to cure on a hotplate at 80ºC for 20 min. After being cured, the elastomer was removed from the master mold and trimmed into individual chambers. A 20-gauge blunt-tipped needle (0.603-mm inner diameter, 0.908-mm outer diameter) (McMaster Carr, Elmhust, Illinois) was used to create input and output holes for the two inlets and shared outlet. The microfluidic chambers were subsequently mounted onto cover glasses (Thermo Fisher Scientific, Waltham, Massachusetts).