Abstract
This work designed a new tilt manipulation stage based on the electrowetting-on-dielectric (EWOD) principle as the actuating mechanism and investigated the performance of that stage. The stage was fabricated using a universal MEMS (Micro-Electro-Mechanical System) fabrication method. In the previously demonstrated form of this device, the tilt stage consisted of a top plate that functions as a mirror, a bottom plate that was designed for changing the shape of water droplets, and supporters that were fixed between the top and bottom plate. That device was actuated by a voltage applied to the bottom plate, resulting in a static electric force actuating the shape change in the droplets by moving the top plate in the vertical direction. Previous experimental results indicated that that device can tilt at up to ±1.8°, with a resolution of 7 μm in displacement and 0.05° in angle. By selecting the best combination of the dielectric layer, the tilt angle was maximized. The new device, fabricated using a common and straightforward fabrication method, avoids deflection of the top plate and grounding in the bottom plate. Because of the limit of Teflon and other MEMS materials, this device has a tilt angle in the range of 3.2-3.5° according to the experimental data for friction and the EWOD device limit, which is close to 1.8°. This paper also describe the investigation of the effects of various parameters, e.g., various dielectric materials, thicknesses, and droplet type and volume, on the performance of the stage. The results indicate that the apparent frictions coefficient of the solid-liquid interface may remain constant, i.e., the friction force is proportional to the normal support force and the apparent frictions coefficient.
Highlights
With the development of micro-fabrication techniques, precise control and manipulation of micro, nano- or even pico-liter volumes have become the core features of a lab-on-a-chip system
If droplets are intended to move, they should overcome the resistance from solid surface. It can be inferred from the above results that the apparent frictions coefficient of the solid-liquid interface remains constant, i.e., the friction force is proportional to the normal support force and the apparent frictions coefficient
To observe whether the square wave and voltage are exerted on the electrodes of the EWOD device, 8 yellow LEDs are connected in series with the PIC, and 8 red LEDs are connected in series with the field-effect transistors (FETs) output
Summary
Preston D J19 designed and fabricated a similar device that used a unique technology to form a super hydrophobic surface, functionalizing the CuO with a monolayer of trichloro(1H,1H,2H,2H-perfluorooctyl)silane They patterned the super-hydrophobic surface using an end mill with a diameter of approximately 1.5 mm. (These technologies are uncommon in MEMS.) the device featured a small angle change of only 1◦ and a low resolution of 10 μm It is previously conducted a friction test experiment.[32] That experiment used EWOD as actuation and a steel spring as a sensor to measure the friction. The relationship between the contact angles and the voltages with different dielectric materials, thickness, and droplet type and volume was investigated. This new device is fabricated using a common and straightforward fabrication method. The device avoids deflection of the top plate by grounding in the bottom plate, which may cause a large angle error
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