A rapid and controllable acoustothermal microheater using thin film surface acoustic waves

Temperature control within a microreactor is critical for biochemical and biomedical applications. Recently acoustothermal heating using surface acoustic wave (SAW) devices made of bulk LiNbO3 substrates have been demonstrated. However, these are generally fragile and difficult to be integrated into a single lab-on-a-chip. In this paper, we propose a rapid and controllable acoustothermal microheater using AlN/Si thin film SAWs. The device's acoustothermal heating characteristics have been investigated and are superior to other types of thin film SAW devices (e.g., ZnO/Al and ZnO/Si). The dynamic heating processes of the AlN/Si SAW device for both the sessile droplet and liquid within a polydimethylsiloxane (PDMS) microchamber were characterized. Results show that for the sessile droplet heating, the temperature at a high RF power is unstable due to significant droplet deformation and vibration, whereas for the liquid within the microchamber, the temperature can be precisely controlled by the input power with good stability and repeatability. In addition, an improved temperature uniformity using the standing SAW heating was demonstrated as compared to that of the travelling SAWs. Our work shows that the AlN/Si thin film SAWs have a great potential for applications in microfluidic heating such as accelerating biochemical reactions and DNA amplification. (C) 2020 Elsevier B.V. All rights reserved.

在微反应器中，温度控制对生化和生物医学应用至关重要。最近，利用由块状铌酸锂（LiNbO₃）衬底制成的表面声波（SAW）器件进行声热加热已得到验证。然而，这些器件通常易碎，且难以集成到单个芯片实验室中。在本文中，我们提出了一种使用氮化铝/硅（AlN/Si）薄膜表面声波器件的快速且可控的声热微加热器。对该器件的声热加热特性进行了研究，其性能优于其他类型的薄膜表面声波器件（例如，氧化锌/铝（ZnO/Al）和氧化锌/硅（ZnO/Si））。对氮化铝/硅表面声波器件在固定液滴以及聚二甲基硅氧烷（PDMS）微腔室内液体的动态加热过程进行了表征。结果表明，对于固定液滴加热，由于液滴显著变形和振动，在高射频功率下温度不稳定；而对于微腔室内的液体，温度可通过输入功率精确控制，具有良好的稳定性和重复性。此外，与行波表面声波相比，驻波表面声波加热的温度均匀性得到了改善。我们的工作表明，氮化铝/硅薄膜表面声波在微流体加热应用中具有很大潜力，例如加速生化反应和DNA扩增。（C）2020爱思唯尔有限公司。保留所有权利。