Design and fabrication of an electrohydrodynamically actuated microlens with areal density modulated electrodes

Abstract

In this paper, we introduce an electrode design for electrohydrodynamically actuated liquid microlenses. The effective electrode areal density radially increases which results in centering of the liquid tunable microlens with a planar device structure. A model was developed to demonstrate the centering mechanism of the liquid microlens. 3D electrostatic simulation was conducted and validity of the idea was examined. A simple fabrication process was developed that uses a surface modified SU-8 as the insulator. The focal length of the microlens was measured to vary from 10.1 mm to 5.8 mm as the voltage varied from zero to 100 V.

Double-Sided Design of Electrodes Driving Tunable Dielectrophoretic Miniature Lens

“…Similar to SU-8 2002, the adhesion of SU-8 50 to glass was improved by ramped baking. As the final step for the bottom substrate, a surface treatment was performed inside a plasma chamber with sulfur hexafluoride (SF 6 ) to make the SU-8 surface more hydrophobic [12]. …”

“…In the second category, the lens profile can be reshaped through various mechanisms with or without an elastic membrane. Some examples of actuation are fluidic (pneumatic) pressure [7], thermal [8], stimuli-responsive hydrogel [1], [9], ferrofluidic piston [10], acoustic waves [11], electrowetting [12]–[14], and dielectrophoretic (DEP) [15]–[17]. The electrowetting and the dielectric mechanisms are sometimes referred to as electrohydrodynamic actuations.…”

A Liquid Optical Phase Shifter With an Embedded Electrowetting Actuator

“…Furthermore, on the bottom substrate, a plurality of interdigitated electrodes are defined and covered by an SU8 insulating layer. When a voltage is applied to the interdigitated electrodes, water, being used as conductive liquid “A”, is pulled into the channel via electrowetting [9]. Hence the silicone oil that is used as the liquid “B” is pushed inward.…”

Fabrication and Actuation of an Electrowetting Droplet Array on a Flexible Substrate

“…Each electrowetting cell in the array is composed of areal density modulated electrodes (shown in Figure 1 ) which we previously demonstrated provided good electrowetting actuation [ 14 ], but which have now been patterned on a flexible PDMS substrate. The electrodes are insulated by a dielectric layer with a patterned hydrophobic region over the electrodes as well as a PDMS ring to create a well which contains the two immiscible liquids actuated by the electrowetting.…”

“…As voltage is applied across the underlying areal density modulated electrodes, the liquids in the electrowetting cell will shift to minimize the potential energy of the system, since minimizing the potential energy is equivalent to maximizing the capacitance of the system according to Equation (1): where is the potential energy of the system, is the charge, and is the capacitance. By design, the potential energy can only be at a minimum when the silicone oil droplet is centered over the areal density modulated electrodes [ 14 ]. As the voltage across the underlying electrodes is increased, the conductive water, which functions as a floating electrode, is attracted down toward the electrodes to minimize the energy in the system by minimizing the distance between itself and the underlying electrodes.…”