Design and fabrication of compound varifocal lens driven by polydimethylsiloxane film elastic deformation

A compound varifocal lens based on electromagnetic drive technology is designed and fabricated, where the polydimethylsiloxane(PDMS) film acts as a driving component, while the PDMS biconvex lens and the plane-concave lens form a coaxial compound lens system. The plane-concave lens equipped with driving coils is installed directly above the PDMS lens surrounded by the annular magnet. When different currents are applied, the annular magnet moves up and down, driving the PDMS film to undergo elastic deformation, and then resulting in longitudinal movement of the PDMS lens. The position change of the PDMS lens changes the focal length of the compound lens system. To verify the feasibility and practicability of this design, a prototype of our compound lens system is fabricated in experiment. Our proposed compound lens shows that its zoom ability reaches 9.28 mm when the current ranges from -0.20 A to 0.21 A.

Mechanism of contact angle saturation and an energy-based model for electrowetting

Electrowetting,as a well-known approach to increasing droplet wettability on a solid surface by electrical bias,has broad applications.However,it is limited by contact angle saturation at large voltage.Although several debated hypotheses have been proposed to describe it,the physical origin of contact angle saturation still remains obscure.In this work,the physical factors responsible for the onset of contact angle saturation are explored,and the correlated theoretical models are established to characterize electrowetting behavior.Combination of the proper 3-phase system employed succeeds in dropping the saturating contact angle below 25？,and validates that the contact angle saturation is not a result of devicerelated imperfection.

Contact angle hysteresis in electrowetting on dielectric

Contact angle hysteresis(CAH) is one of the significant physical phenomena in electrowetting on dielectric(EWOD).In this work, a theoretical model is proposed to characterize electrowetting evolution on substrates with CAH, and the relationship among apparent contact angle, potential, and some other parameters is quantified. And this theory is also validated experimentally. The results indicate that our theory and equation based on energy balance succeed in describing the electrowetting response of potential with significant contact angle hysteresis. The CAH in EWOD, ranging from 0° to about 20° in electrowetting cycle, increases with the increase of voltage and climbs up to about 20° when voltage is increased to about 38 V, and then decreases to zero with the further increase of voltage.

Simulation of beam steering control in arrayed liquid prisms system based on electrowetting-on-dielectric

In this paper,an arrayed liquid prisms system based on electrowetting-on-dielectric(EWOD)is proposed to modulate the three-dimensional beam steering control.The relationships between beam steering control range,electrowetting contact angle,and liquid refractive index are derived.COMSOL is employed to demonstrate the beam steering control properties of the electrowetting-based arrayed liquid prisms when bias voltages are applied.The influence of contact angle,liquid refractive index,and interval between adjacent prisms are discussed.The results show that the beam steering control performance of the system will be greatly improved,and the range of beam steering angle is−20°to 20°by selecting optimum combinations of liquids and rational interval between adjacent prisms.The arrayed liquid prisms system can succeed to achieve continuous control of beam steering in a conical region with an apex angle of 40°,and the vertex of the circular cone is located at the 15.02 mm in the z-axis.The proposed system will promote the development of non-mechanical beam steering technology and have a wide range of applications.

Electrowetting-driven droplet shrinkage with tunable focus property

In this paper, a non-conductive droplet driven by electrowetting(EW) with planar electrode in surrounding fluid is studied. COMSOL is employed to simulate the evolution of droplet shrinkage and the relative experimental setup is established to monitor the evolution of contact angle and height at different voltages. The droplet contracts inward and the corresponding contact angle/height increase when voltage increases. When the voltage ranges from 50 V to 140 V, the variation of the relative contact angles and height reach up to 118.78° and 3.194 mm, respectively. The system of silicon oil and surrounding liquid propylene glycol(PG) acts as a positive lens, whose focal length varies from 87.153 mm to 42.963 mm.