FUNDAMENTALS
Digital Microfluidics and Electrowetting (EWOD)
Digital microfluidics moves individual droplets around a grid of electrodes — splitting, merging and mixing them on demand, with no channels or pumps. The key trick is electrowetting. Here is how it works.
What is digital microfluidics?
Digital microfluidics is distinct from channel ("continuous-flow") microfluidics. Instead of fluid in fixed channels, discrete droplets sit on an array of electrodes and are moved by switching voltages — fully programmable, a bit like addressing pixels on a screen.
Electrowetting on dielectric (EWOD)
The actuation mechanism is electrowetting on dielectric. Applying a voltage to an electrode changes the apparent wettability of the surface beneath a droplet, so the droplet spreads toward the energised electrode. By sequencing voltages across the array, droplets can be transported, split, merged and mixed.
Why it is powerful
- Protocols are reconfigured in software — no fixed channels to redesign.
- Each droplet is an independent reaction vessel.
- Low reagent consumption, good for automated sample prep and assays.
Trade-offs
EWOD needs patterned electrodes and control electronics, and droplet evaporation and biofouling have to be managed. Throughput and use cases differ from continuous-flow droplet microfluidics.
Digital vs continuous-flow microfluidics
Digital microfluidics individually addresses droplets on electrodes; continuous-flow microfluidics moves streams and droplets through channels (often with pumps). They suit different problems — digital for flexible, low-volume automation; continuous-flow for high-throughput, steady processes.
Frequently asked questions
What is digital microfluidics?
A technique that moves discrete droplets across an array of electrodes by switching voltages, allowing programmable transport, splitting, merging and mixing without channels or pumps.
What is EWOD?
Electrowetting on dielectric — applying a voltage changes the wettability under a droplet so it moves toward the energised electrode, the actuation mechanism behind digital microfluidics.
How is digital microfluidics different from droplet microfluidics?
Digital microfluidics addresses individual droplets on electrodes; droplet (continuous-flow) microfluidics generates and flows droplets through channels. They differ in control, throughput and applications.
What are the limitations of EWOD?
It requires patterned electrodes and control electronics, and droplet evaporation and surface biofouling must be managed.
Programmable droplets
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