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.