Dr. Seungtae Choi Profile

Dr. Seungtae Choi

at Samsung Advanced Institute of Technology

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Proceedings Article | 22 August 2009 Paper

Microfluidic design and fabrication of wafer-scale varifocal liquid lens

Jeong-Yub Lee, Seung-Tae Choi, Seung-Wan Lee, Woonbae Kim

Proceedings Volume 7426, 742603 (2009) https://doi.org/10.1117/12.825064

KEYWORDS: Liquids, Liquid lenses, Microfluidics, Silicon, Actuators, Semiconducting wafers, Wafer-level optics, Lens design, Oxygen, Electroactive polymers

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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.

Proceedings Article | 24 February 2009 Paper

Liquid-filled varifocal lens on a chip

Seung Tae Choi, Jeong Yub Lee, Jong Oh Kwon, Seungwan Lee, Woonbae Kim

Proceedings Volume 7208, 72080P (2009) https://doi.org/10.1117/12.811401

KEYWORDS: Actuators, Microfluidics, Polymers, Polymeric actuators, Electroactive polymers, Semiconducting wafers, Multilayers, Opacity, Silicon, Wafer-level optics

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In this study we developed a liquid-filled varifocal lens operated by electroactive polymer actuators. A silicon wafer was structured with micromachining processes to have four microfluidic chambers and a circular hole working as an aperture. The structured silicon wafer (opaque frame) was bonded to a glass wafer (transparent frame), and thus microfluidic channels were formed between them. Top surface of the main frame was covered with a transparent elastomer membrane, and the internal volume confined by the membrane and the two frames was filled with optical fluid. In order to operate this varifocal lens system, multilayered P(VDF-TrFE-CFE) [poly(vinylidene fluoride-trifluoroethylene-clorofluoroethylene)] polymer actuators were also developed, which show relaxor ferroelectric behavior, and thus produce large electrostrictive strain. When an electric field is applied, the multilayered P(VDF-TrFE-CFE) polymer actuators push the optical fluid so that the elastomer membrane together with the internal fluid changes their shape, which alters the light path of the varifocal lens. The original shape of the elastomer membrane is restored by the elastic recovery of the P(VDF-TrFE-CFE) actuators when an applied electric field is removed. We observed that with the applied voltage of 40 V the varifocal lens changes the optical power of more than 30 diopters within 20 ms. Optical analysis showed that the deformation shape of the optical membrane can be successfully used to design phone camera modules with auto-focus function.

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