Numerical and experimental investigations of interdigital transducer configurations for efficient droplet streaming and jetting induced by surface acoustic waves

Research output: Contribution to journalArticlepeer-review


  • Mehdi H. Biroun
  • Mohammad Rahmati
  • Mehdi Jangi
  • Baixin Chen
  • Yong Qing Fu

Colleges, School and Institutes

External organisations

  • Northumbria University Newcastle
  • Heriot-Watt University


Surface acoustic wave (SAW) based technologies have recently been explored for various sensing and microfluidic applications, and numerous experimental studies and numerical modelling of SAW streaming and liquid-solid interactions have been performed. However, the large deformation of droplet interface actuated by SAWs has not been widely explored, mainly due to the complex physics of SAW-droplet interactions and interfacial phenomena. In this paper, a computational interface tracking method is developed based on the couple level set the volume of fluid (CLSVOF) approach to simulate the interactions between liquid and acoustic waves and deformation of the liquid-air surface. A dynamic contact angle boundary condition is developed and validated by experimental results to simulate the three-phase contact line dynamics. The modified CLSVOF method is then used to study the droplet jetting and internal streaming behaviours by analyzing the energy terms within the liquid medium. Furthermore, by applying the numerical model, effects of configurations and positions of two interdigital transducers (IDTs) on droplet actuation have been investigated to achieve efficient mixing, separation, and jetting. Results show that two perfectly aligned IDTs are optimal for mixing applications. In contrast, two offset IDTs are optimal for concentration and separation applications. The maximum jetting velocity and minimum jetting time are achieved by using a pair of aligned IDTs, whereas by using the two offset IDTs, effective liquid mixing and jetting are observed which can be used in bioprinting applications.

Bibliographic note

Funding Information: This work was financially supported by the UK Engineering, and Physical Sciences Research Council (EPSRC) grants EP/P018998/1, and Special Interests Group of Acoustofluidics under the EPSRC-funded UK Fluidic Network (EP/N032861/1). Publisher Copyright: © 2020


Original languageEnglish
Article number103545
Number of pages11
JournalInternational Journal of Multiphase Flow
Early online date18 Dec 2020
Publication statusPublished - Mar 2021


  • Surface acoustic wave, Droplet jetting, Acoustic streaming, CLSVOF, Interdigital transducer