A soft-polymer piezoelectric bimorph cantilever-actuated peristaltic micropump.

A peristaltic micropump was fabricated and characterized. The micropump was fabricated using soft lithography, and actuated using piezoelectric bimorph cantilevers. The micropump channel was formed by bonding two layers of PDMS, mixed at 5:1 and 30:1 ratios. The channel was fabricated in the 5:1 layer using replica molding (REM), where a very simple and inexpensive template was made by straddling a 75 microm wire over a glass substrate, followed by covering and smoothing over the wire with a piece of aluminium foil. Not only was this template inexpensive and extremely simple to fabricate, it also created a rounded cross-sectional geometry which is favorable for complete valve shutoff. The cantilevers were driven at Vp=+/-90 V with amplified square wave signals generated by a virtual function generator created in LabVIEW. Connections to the micropump were made by placing capillary tubes in the channel, and then sealed between the two layers of PDMS. Machined aluminium clamps were adhered to the tips of the cantilevers with general purpose adhesive. These clamps allowed for aluminium valves, with finely machined tips of dimensions 3 mm by 200 microm, to be held firmly in place. The variables characterized for this micropump were flow rate, maximum attainable backpressure, free cantilever deflection, valve shutoff, and valve leakage. Three actuation patterns with phase differences of 60, 90, and 120 degrees were compared for flow rate and maximum backpressure. It was determined that the 120 degrees signal outperformed the 60 degrees and 90 degrees signals for both maximum flowrate and maximum attainable backpressure. The maximum and minimum flowrates demonstrated by the micropump were 289 nL min(-1) and 53 nL min(-1), respectively. The maximum backpressure attained was 35 300 Pa. It was also demonstrated that the valves fully closed the channels upon actuation, with minimal observed leakage.