A thermally shielded acoustofluidic device for robust particle focusing

Temperature control is crucial when handling biological particles. In acoustofluidics, temperature regulation is also critical since its fluctuations induce resonance shifts that deteriorates the acoustophoretic performance. In this work, we present a novel simple design that thermally decouples a microfluidic chip from the piezoelectric actuator through a thin copper sheet, allowing precise temperature control of the chip. By automating our experimental setup, we obtained precise multiparameter control and characterization of the device, which allows studying how the effects of flowrate, input power, voltage, temperature and frequency affect the acoustic focusing performance. We show that constant power is the preferred electrical excitation method to minimize temperature fluctuations within a broad frequency range. We investigated the performance of the device at different set temperatures and found heat-induced resonance shifts and performance degradation close to physiological temperature. Our work confirms that the design enables precise temperature control, which is essential for robust performance, especially at high input power to the piezoelectric transducer. This work lays the basis for future optimized acoustofluidic devices able to focus particles reproducibly and efficiently at high throughput.