Towards efficient surface acoustic wave (SAW)-based microfluidic actuators

Abstract

The applicability of surface acoustic wave (SAW) based actuators was demonstrated for a variety of microfluidic tasks, including fluid mixing, particle separation, localized heating or fluid atomization. But as traditionally the main field of application lies in high-frequency telecommunication, SAW devices are only marginally optimized for microfluidics, especially in respect to an energy efficient operation. In lab setups incorporating SAW-based microfluidic actuators, insufficient energy efficiency resulting e.g. from interdigital transducers (IDTs) with inadequate electrical impedance, absorption of SAW power in vessel walls or maladjusted wavelengths, is often simply counteracted by an increase of the output power of the signal source. For the operation of portable or highly integrated devices, though, or for devices with high power needs, energy efficiency is crucial. Additionally, an inefficient mode of operation can result in severe device degradation.In order to extend the performance of SAW actuators, we discuss different approaches regarding the optimization of their power efficiency and provide selected experimental results, highlighting the importance of the governing power loss effects. Depending on the intended microfluidic task, several of the demonstrated optimization strategies can be combined and – as will be shown – considerable improvements in the device performance can be achieved.