Analysis of heat generation and transfer in droplet-based acoustofluidic by considering the attenuation effect

The droplet-based acoustic microfluidic system has recently demonstrated excellent performance and application potential in biological micro/nanoparticle manipulation, chemical synthesis, and materials science. However, in those applications with obvious temperature response, the heat generation of droplets under the action of surface acoustic waves (SAW) is ignored usually, which highlights the need to analyze the process of SAW heating droplets to guide temperature control. Here, based on the system with relative acoustic field bias arrangement, the influence of SAW attenuation on the distribution of heat sources was studied by constructing a coupled model of heat source heating and fluid heat transfer. The role of SAW attenuation effect on the initial stage of droplet heat generation was analyzed through experiments and simulations, and the mechanism of local heat sources on droplet heat generation was clarified. The temperature field of droplets was determined by the local heat source caused by SAW attenuation and the convective heat transfer generated by the acoustic streaming effect. The correspondence between input power and temperature field was also analyzed, to clarify the scheme for adjusting droplet temperature. This work clarifies the temperature control mechanism of this acoustic systems and enables applications such as biochemical reactions or DNA (deoxyribonucleic acid) amplification.