Research at MNRL


Surface Acoustic Wave Microfluidics

Surface acoustic waves (SAWs) are nanometre order electroelastic analogues of earthquake waves that propagate along the surface of a piezoelectric substrate. Due to the fluid-structural coupling between the undulations along the substrate surface and the fluid above the substrate, substantial acoustic energy is transferred into the fluid, which can then be exploited to drive a wide range of microfluidic phenomena. Our research has resulted in the discovery of a wide range of new phenomena and we seek to elucidate fundamental theories that underpin the physicochemical mechanisms responsible for these observations. The localisation of the energy of the SAW in a small region of the substrate produces extremely large surface accelerations (several millions of g’s) allows us to drive extremely fast microfluidics, at least one to two orders of magnitude faster than currently available electrokinetic devices. Strategies for ultrafast microchannel pumping, drop transport, microcentrifugation, particle sorting and concentration, jetting and atomisation are currently being developed for a wide range of biomicrofluidic applications including drug delivery, point-of-care medical diagnostics, biosensors and high throughput drug screening. 

More on SAW microfluidics


Research Overview

Research at the Micro/Nanophysics Research Laboratory (MNRL) revolves around investigating the fundamental physicochemical hydrodynamics associated with electrically and acoustically driven microfluidic transport using a host of advanced visualisation and characterisation equipment as well as analytical, semi-analytical and fully numerical techniques. In addition, we also seek to apply these fundamental studies to novel ways for actuating and manipulating both fluids and particles in microscale and nanoscale devices for various biomicrofluidic applications such as drug delivery, high-throughput drug screening, biosensor technology, robotic surgery and other lab-on-a-chip type applications. Some of our research projects are listed below.

Electrokinetically-Driven Microfluidics

Our work on electrokinetics primarily deals with that involving interfaces. We have pioneered the development of a high frequency (> 10 kHz) alternating current (AC) electrospray technique as well as a novel microcentrifugation technique driven by electrohydrodynamic air thrust (ionic wind). The former, which generates micron order electroneutral aerosol droplets, distinct from its direct current (DC) counterpart, has tremendous implications for drug delivery. Moreover, we have also shown its potential for the drug encapsulation in biodegradable polymeric particles for controlled release drug delivery as well as for the synthesis of polymeric fibers. The latter has been demonstrated as an efficient mechanism for driving intense micro-mixing as well as particle concentration (such as the separation of red blood cells from plasma). We have also developed theoretical and numerical models to describe electrowetting phenomena, which constitutes a highly controllable method for the transport of fluids in microfluidic devices using electric fields.

Interfacial Flows, Liquid-Liquid Dispersions & Nanodroplets

Numerical techniques are employed to investigate the dynamics of thin liquid films under the influence of Marangoni (surface tension gradients) and thermocapillary (thermal gradients) stresses in the context of wetting and dewetting in coating flows as well as the drainage of the interstitial liquid trapped between two coalescing drops in an immiscible liquid medium. We show that the latter process has implications on the control of phase inversion of liquid-liquid dispersions or emulsions. 

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