A paper-based microfluidic switch activated by surface acoustic waves

A microfluidic switch is indispensable for a programmable paper-based microfluidic device. A new paper-based microfluidic switch, which could be activated by surface acoustic wave (SAW), was presented. The presented microfluidic switch was consisted of a PDMS micro-shelf and a three-fold paper channel. The PDMS micro-shelf was mounted on a (XY)/128° LiNbO₃ substrate, on which a pair of interdigital transducers (IDTs) with 27.5 MHz working frequency and two reflectors were fabricated. The folded paper channel was fixed on the PDMS micro-shelf using PDMS micro-wedges. When a RF signal with 27.5MHz frequency was applied to the IDTs, two SAWs were generated. And the microfluid on the piezoelectric substrate was transported to the folded paper channel by SAWs. Then, the folded angles of the folded paper channel were increased so that the folded paper channel could connect with two paper-based microchannels waiting for connection to implement the function `on´ of the switch. Red dye solution microfluid has been successfully used to demonstrate the switch function. The work is valuable for a programmable paper-based microfluidic device.