Particle directed dual-fluid flow driven by electrowetting for controllable multiway light valves

High efficiency and position controllable multiway light valves are achieved by electrowetting-driven and magnetic particle (MP)-directed oil film dewetting in microscale spaces. The non-transparent oil phase can be attracted to oleophilic MPs and repelled from hydrophilic MPs to adjust the oil film distribution in a microwell (valve area). Thus, in an oil-water dual-fluidic system, the dewetting and breakup point of an oil film can be modulated when driven by electrowetting. By introducing a MP, both the switching speed and opening ratio of a light valve (microwell) are increased, and the time of both starting to open and reaching the maximum opening ratio is reduced. Oleophilic MPs with larger size show better controllability than hydrophilic MPs with smaller size. A 16-way spatial valve is achieved by magnetically moving one MP in a single microwell. Such a phenomenon is also demonstrated on a large area device with high-density microwells, suggesting high potential for optical valves or display applic...