Droplet IO : programmable droplets for human-material interaction

Abstract

In this thesis, I propose aqueous droplets as a form of programmable material that can computationally transform its physical properties. Liquid matter can undergo physical transformation through interfacial forces and surface tension. I introduce a system called DropletIO to regulate interfacial forces through a programmable electric field. The system can actuate and sense macro-scale (micro-liter to milli-liter) droplets on arbitrary planar and curved surfaces. The system can precisely move, merge, split, and change shape of droplets and thus enables a range of applications with human interactivity, information displays, parallelized programmable chemistry and dynamically tunable optics. DropletIO system uses electrowetting on dielectric (EWOD) to manipulate droplets. EWOD is a physical phenomenon where a polar droplet on a dielectric surface is attracted to a charged electrode. I constructed EWOD arrays with integrated actuation and sensing on inexpensive printed circuit boards that can scale to arbitrarily large areas and different form factors. Additionally, in this thesis I discuss how semiconductor device scaling applies to electrowetting for smaller volume droplets and hence miniaturized programmable lab-on-a-chip. Droplet based microfluidics is extensively used in biology and chemistry. In this thesis I describe two novel fluid manipulation mechanism for microfluidics. First, I show an approach for splitting aqueous droplets on an open digital microfluidic platform and thus a system capable of performing a complete set of microfluidic operations on an open surface. Second, I demonstrate how electrowetting platforms can handle large volume fluids, and hence enable a new direction in programmable fluid handling called digital millifluidics.