Bistable liquid shutter operated by DEW actuation for multifunctional miniature cameras

Abstract 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 broaden the application of liquid shutters, further exploration of diverse designs optimized from a microfluidic perspective is required to ensure stable performance under vibrational environment. This paper presents a novel bistable 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 developed a dielectrowetting actuator for droplet manipulation and a barrier structure for defining a boundary of the manipulation. To achieve bistable operation of where electrical power is only consumed during the opening and closing operations, barrier structures were designed in consideration of Laplace pressure. Second, a liquid shutter device was fabricated through photolithography, thin film deposition, liquid injection, assembly, and packaging. Especially, dry film resists (DFRs) were used to construct the designed barrier structures of various shapes (solid and dotted patterned barriers) and thicknesses (60, 90, and 120 μ m) within the microfluidic channel, providing different Laplace pressures. Third, we investigated a liquid crystal as the subject of dielectrowetting actuation and as a light absorber. Next, the response and operational stability of the fabricated liquid shutter device were evaluated by adjusting the design specification, driving signal, and vibrational condition. The proposed liquid shutter features a compact design (∼180 μ m in channel height) for miniaturization and operates with low power consumption. These results are expected to contribute to the design of future liquid shutters and similar liquid-based optical devices for multifunctional camera modules with reliable performance.