Biosensing at Drop Scale Assisted by Electrowetting at Moderate Frequency

AbstractThis paper addresses surface ageing of a functionalized substrate in digital microfluidics. A model system based on bovine serum albumin (BSA)-laden sessile drop is selected. AC ElectroWetting-On-Dielectrics (EWOD), increasingly used in digital micro-systems for medical assays, is implemented in coplanar configuration. The small frequency re- quired by EWOD actuation (f =100 - 1000Hz) enables shape oscillations of the latter sessile drop and internal streaming. As demonstrated from dynamic contact angle (DCA) imaging, adsorption of BSA at the solid substrate is promoted un- der EWOD, as also shown from the time-dependent solid-liquid surface pressure. For an oscillating mode, n = 6, our numerical simulations show that corner eddies located near the oscillating contact line yield an efficient molecular re- newal. In this way, oscillating EWOD could be used purposely as a tool to speed up label-free detection from DCA measurements