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Ren, Hongwen,Xu, Su,Wu, Shin-Tson Royal Society of Chemistry 2013 Lab on a chip Vol.13 No.1
<P>We report a dielectrically actuated liquid crystal (LC) pump. A small volume of LC forms a pillar-like droplet in a cylindrical hole which partially touches the bottom substrate with embedded interdigitated electrodes. By applying a voltage, the LC droplet can be largely stretched along the electrode direction by the generated dielectric force, which in turn exerts a pressure to displace a small volume of fluid on the opposite side of the chamber. Once the voltage is removed, the LC droplet returns to its initial state. The LC droplet with such a reciprocating movement behaves like a pump. In this work, the actuation mechanism of the LC pump is presented and the performance evaluated experimentally. Our LC pump has the following advantages: simple structure, easy fabrication, compact size, high precision, low power consumption, and relatively fast response time. It is promising for applications in lens actuators, biotechnology, drug delivery, and other lab-on-a-chip devices.</P>
A Liquid Lens Driven by Bubble Actuator
Lichun Ren,Ran Hee Lee,Hye Ryung Park,Hongwen Ren,Changwoon Nah,Il-Sou Yoo IEEE 2013 Journal of microelectromechanical systems Vol.22 No.5
<P>We report an adaptive-focus lens using two immiscible liquids. The two liquids have a spherical interface and their border is confined by an iris diaphragm (ID). Using a bubble actuator to vary the aperture of the ID, the surface profile of the two liquid is changed, which in turn leads to a tunable focal length. In this paper, the liquid lens structure is depicted and the operation mechanism of the bubble actuator is introduced. For the liquid lens, the refractive index (n<SUB>1</SUB>) of the convex liquid is smaller than that of the concave (or surrounded) liquid (n<SUB>2</SUB>, n<SUB>2</SUB>-n<SUB>1</SUB> ~ 0.2), so the lens is a diverging lens. As the aperture of the diaphragm is changed from ~ 5 to ~ 7.5 mm by the actuator, the focal length (f) of the lens could be tuned in the range of -168 mm ≤ f ≤ -55 mm. For the bubble actuator, it has the advantages of voltage control, large actuation pressure, reasonable speed, and low power consumption. Driven by the bubble actuator, our liquid lens can present a large aperture change, reasonable dynamic response, and precise focus control.</P>
Electrically actuated liquid iris.
Xu, Miao,Ren, Hongwen,Lin, Yi-Hsin Optical Society of America 2015 Optics letters Vol.40 No.5
<P>We report an adaptive iris using dielectric liquids and a radial-interdigitated electrode. A black liquid is confined by a circular gasket with a donut shape. The surrounding of the black liquid is filled with an immiscible liquid. In the relaxing state, the black liquid obtains the largest clear aperture. By applying a voltage, the surface of the black liquid is stretched by the generated dielectric force, resulting in a reduction of its aperture. For the demonstrated iris, the diameter of the aperture can be changed from 4.7??mm to 1.2??mm when the voltage is applied from 0 to 70??V(rms). The aperture ratio is 94%. Owing to the radial-interdigitated electrode, the aperture size of the iris can be effectively switched with a reasonably fast response time. The optical switch is polarization-insensitive. The potential applications of our iris are light shutters, optical attenuators, biomimicry, and wearable devices.</P>
Polymer Network Liquid Crystal (PNLC) Lenticular Microlens Array With No Surface Treatment
Wang, Xiahui,Ren, Hongwen,Wang, Qionghua IEEE 2016 Journal of display technology Vol.12 No.8
<P>A polymer network liquid crystal (PNLC) lenticular microlens array with no surface treatment is prepared. Before polymerization, the LC and diacrylate monomers are reoriented with gradient refractive index distribution by a fringing field. After polymerization, the oriented LC is stabilized by the polymer network. The prepared PNLC lenticular microlens array is optically anisotropic. Without surface treatment, the device fabrication is simplified, and it can present almost the same optical performance as the PNLC lenticular microlens with surface treatment. Integrating with a 90 twisted-nematic LC cell, the PNLC lenticular microlens array can be switched between a focusing state and non-focusing state. Such a PNLC lenticular microlens array has potential application in switchable 2D/3D displays.</P>
Optical properties of poly(vinyl chloride)‐gel‐based microlens arrays
Zhou, Zuowei,Ren, Hongwen John Wiley Sons, Inc. 2019 Journal of applied polymer science Vol.136 No.10
<P><B>ABSTRACT</B></P><P>We use a poly(vinyl chloride) (PVC) gel and an electrode to fabricate adaptive microlens arrays (MLAs). The electrode has a zoned‐array pattern. By applying a direct current voltage to the electrode, the PVC gel on each zoned electrode exhibited the character of a lens. The imaging of the MLA can be analyzed using either an optical microscope or a beam profiler or both. The topography of the PVC gel can be measured using an optical surface profiler. Compared to the imaging and focusing, the topographic map can discover additional information about the performances of the MLA. For example, the focal length of each lens in the MLA can be calculated precisely, and the aberration of the MLA can also be evaluated. Results show that the surface profile is an important factor for characterizing the performance of PVC‐gel‐based MLA. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. <B>2019</B>, <I>136</I>, 47407.</P>