Chapter 4: Digital Microfluidics

Electromechanically driven fluid displacement over solid surfaces has significant advantages over bulk flow regimes, particularly when the fluid volume is in the form of a droplet. Voltage-induced interfacial surface tension alterations at the unbound surface of a droplet increase the droplets' wettability over a hydrophobic surface. This phenomenon is known as electrowetting (EW). Concurrently, the electrical force acting on the droplet volume produces a mechanical force that drives motion. The theories behind droplet motion are covered along with salient limiting factors that need to be considered as theory deviates from observation. Generation of digitised droplets on microarray architectures, referred to as digital microfluidics (DMF), provides confined microenvironments for a range of chemical, biochemical, biological and screening processes to be conducted in volumes ranging from pL to nL. With multiplexing of tasks and automation of processes being developed for full on-chip functionalities, the development of novel architectures and routing strategies for contamination avoidance will be explored along with system demonstrations for sector specific application.