Microfluidic design and fabrication of wafer-scale varifocal liquid lens

摘要

Microfluidic design and fabrication was developed for wafer-scale varifocal liquid lens which is slim less than 0.9mm. The liquid-filled varifocal lens has advanced functions such as auto macro and focusing to obtain a high quality of image. This varifocal lens is similar to human eye and it consists of main Si frame which has penetrated inner hole, upside-bonded PDMS (polydimethylsiloxane) elastomer membrane, downside-bonded glass plate and optical fluid confined by these structures. Si frame, which has a circular hole for tunable lens chamber, several holes for actuator chamber and micro-fluidic channels between chambers, is fabricated using thin Si wafer and microelectromechanical system (MEMS) processes. When optical fluid is filled the internal cavity by conventional injection, void trapping which degrades optical performance or filling impossibility happens because of high aspect ratio between lens diameter and thickness for slim liquid lens. To prevent these problems, we developed wafer-based microfabrications of seal line dispensing, accurate dropping of optical fluid, pressing & bonding process in vacuum and UV sealant curing. Afterward, electro-active polymer actuators, which push the optical fluid to change the lens shape, was attached on the PDMS membrane of liquid lens wafer and sawing process of 9.4mm*9.0mm chip size followed. Finally, the varifocal liquid lens which is slim less than 0.6mm thickness (0.9mm included actuators), tunable more than 20diopter changes of refractive power, guaranteed reliability of 300,000 repetitions and suitable for mass production, was realized.