Modular, dual-tone piezoelectric micropump driver for low-cost, portable droplet generation

Piezoelectric micropumps are commonly used in microfluidics and specifically droplet generation. However, flow control poses technical challenges due to the pump’s pulsatility. We previously demonstrated a portable system (CogniFlow-Drop) for proportional-integral-derivative (PID) controlled droplet generation in a highly responsive manner with commercial piezoelectric micropumps that could generate droplets of adjustable size with a coefficient of variability (CV%) broadly between 5-10%. However, we noted the importance of control resolution and the shape of the driving waveform, as well as a general lack of compact piezoelectric drivers on the market, which have on-board waveform generators and were capable of finer waveform control. Thus, in this work, a low-cost compact, broad-use piezoelectric micropump driver is presented and characterized in use on the CogniFlow-Drop platform. The designed driver features an on-board waveform source, using two frequency-adjustable analog oscillators. The primary and secondary oscillations are summed to offer an option for a dual-tone pump-driving waveform. The design includes two voltage controlled differential amplifiers which can be adjusted externally to scale the secondary waveform and the sum of the two. Integrating two of the custom drivers into CogniFlow-Drop, the preliminary results showed overall improvements in droplet size CV%, bringing the average below 5%.