PDMS-based microfluidic devices using commoditized PCBs as masters with no specialized equipment required

Designed printed circuit boards (PCBs) are alternative substrates for master mold construction of microfluidic devices. However, the rough supportive material molds rough replicas and causes difficulty in device sealing. To overcome this difficulty, a copper layer is used to generate a smooth surface. Some other researchers have used thermoplastic elastomers, which are typically much easier to bond, instead of the general polymer polydimethysiloxane (PDMS). This study presents an extremely simple approach for fabricating PDMS-based microfluidic devices using PCBs as masters. Unlike those reported in the previous studies, commoditized PCBs fabricated at a common PCB manufactory were directly used as the master molds. Two layers of semi-cured silicone of a distinct base to curing agent ratios were bonded together by additional curing. Efficient bonding was accomplished and avoided insufficient adhesion due to the rough surfaces of the PDMS replicas. Highly monodisperse droplets with polydispersity values smaller than 1% were stably formed using the easy fabricated devices. Essential operations in droplet microfluidics were reliably conducted in the PDMS-based devices. Moreover, the droplets were orderly sorted by the microstructures in the fabricated multi-height devices. The fabrication process provided a simple, convenient and reliable approach to prepare the general polymer PDMS-based microfluidic devices with a minimal requirement for equipment.