Bistable Liquid Shutter Operated by DEW Actuation for Multifunctional Miniature Cameras

To overcome the limitations of conventional mechanical optical elements, liquid-based optical devices such as a lens, prism, iris, and shutter have been proposed and studied since the 2000s. Among these liquid-based devices, various liquid shutter concepts have been presented to attenuate or block incident light in optical switching and imaging systems. To expand application of liquid shutters, more research still is needed on systemic design and validation under various conditions. This paper presents liquid shutter operated by dielectrowetting actuation for high-performance and multifunctional camera modules. The opening and closing of the liquid shutter are achieved by controlling the position of an opaque droplet in a microfluidic channel with a dielectrowetting actuator. First, we designed a dielectrowetting actuator for droplet manipulation and a barrier structure for defining a boundary of the manipulation. Second, a prototype sample was fabricated through a wafer-level process. To realize bistable operation where an electrical power is consumed only during opening and closing operations, barrier structures made of dry film resist were fabricated with different shapes and dimensions, considering Laplace pressure. Third, we investigated the characteristics of the fabricated liquid shutter in terms of optical performance, threshold voltage, and operation speed. Finally, the liquid shutter devices were evaluated under in a vibration environment to evaluate operation stability.