By focussing two opposing surface acoustic waves to a point on the substrate directly beneath a liquid drop, it is possible to concentrate the leakage of acoustic energy into the drop such that sufficient inertial stresses are generated within the drop to overcome the capillary stress resulting in the deformation of its drop interface into a coherent cylindrical liquid column. The jet that eventuates remarkably persists over several centimetres in length despite originating from a millimetre order diameter drop without requiring any nozzles or orifices. Eventually, the elongated jet suffers from the classical Rayleigh-Plateau instability through which the liquid column becomes unstable to axisymmetric perturbations and consequently breaks up into one or more droplets.
- MK Tan, JR Friend, LY Yeo. Interfacial Jetting Phenomena Induced by Focused Surface Vibrations. Phys Rev Lett 103, 024501 (2009).
- PK Bhattacharjee, AG McDonnell, R Prabhakar, LY Yeo, J Friend. Extensional Flow of Low-Viscosity Fluids in Capillary Bridges Formed by Pulsed Surface Acoustic Wave Jetting. N J Phys 13, 023005 (2011).
- AG McDonnell, TC Gopesh, J Lo, M O’Bryan, LY Yeo, JR Friend, R Prabhakar. Motility Induced Changes in Viscosity of Suspensions of Swimming Microbes in Extensional Flows. Soft Matter 11, 4658–4668 (2015).
- AG McDonnell, NN Jason, LY Yeo, JR Friend, W Cheng, R Prabhakar. Extensional Viscosity of Copper Nanowire Suspensions in an Aqueous Polymer Solution. Soft Matter 11, 8076–8082 (2015).
- JO Castro, SR Ramesan, AR Rezk, LY Yeo. Continuous Tuneable Droplet Ejection via Pulsed Surface Acoustic Wave Jetting. Soft Matter 14, 5721–5727 (2018) Article coverart selected as journal front cover; Correction: pp 5937–5938].
- JO Castro, SR Ramesan, HD Dang, AR Rezk, LY Yeo. Acoustopipetting: Tuneable Nanoliter Sample Dispensing Using Surface Acoustic Waves. Anal Chem 91, 5621–5628 (2019).