Control of an electrowetting-based beam deflector

Abstract

We experimentally demonstrate the feasibility of a small, low-power beam deflector based on electrowetting. The beam deflector deflects light by refraction at the flat interface (meniscus) between two immiscible and density-matched liquids, namely, a nonpolar oil mixture and an aqueous salt solution. The liquids are contained in a square pyramidal frustum with electrode-covered faces. The electrodes can be separately driven by voltage sources in order to control the contact angle between the meniscus and the frustum faces. By controlling the voltage on all four electrodes, a flat meniscus is obtained that can be tilted independently in two perpendicular directions. We present a capacitance-based feedback driving scheme and demonstrate that it can be used for accurate control of the meniscus shape and tilt. Independent, continuous, and accurate beam steering through an angle of ±6° was achieved on two deflection axes.

Simultaneous beam steering and shaping using a single-interface optofluidic component

“…36 The former is addressed using measured contact angle curves while the influence of the latter is reduced to some degree by the applied AC voltage and could be reduced further by incorporating wetting feedback. 37,38 Material inconsistencies, such as fluid density mismatch, local differences in wetting characteristics or simply manufacturing and assembly tolerances negatively impact the scanning accuracy but can be compensated by performing calibration. 39 The scanning speed depends on the liquid properties that are identical to the ones used in the 16-electrode device.…”

A Study of Dip-Coatable, High-Capacitance Ion Gel Dielectrics for 3D EWOD Device Fabrication

“…This lab-on-a-wristband (LOW) concept highlights the potential of 3D EWOD technology for point-of-care (POC) applications. Another example of the 3D EWOD devices popularly studied in recent years is the liquid prism that enables spatial beam steering [ 18 , 19 , 20 , 21 , 22 , 23 ]. EWOD-driven liquid prism technology has been used in diverse applications including sunlight beam steering for solar energy harvesting [ 24 , 25 , 26 ] and optical beam control to achieve a Fresnel lens [ 23 ].…”

“… Experimental demonstrations of beam steering with the dip-coatable 3D liquid prisms. ( A ) The top images show the beam deflection using a single prism; ( a ) At ϕ = −25°, the beam steering was achieved as large as β = −8.82°; ( b ) At ϕ = 0°, a laser beam passes perpendicularly through the interface; ( c ) Similarly, we can achieve beam steering of β = 8.40° at φ = 24° (reprinted from the Reference [ 20 ] with the permission). ( B ) The bottom images present arrayed liquid prims that enable 3D focal tuning by controlling arrayed prisms; ( a ) When all steering angles are zero, β a1 = β a2 = β a3 = 0°, the Fresnel lens does not perform as a concentrating element (i.e., f a = ∞); ( b ) When the outer prisms are modulated such that the steering is β b1 = −3.2°, β b3 = 3.3° and β b2 remains at 0°, the beams converge and the lens is then said to have a focal length at ƒ b ≈ 525 mm; ( c ) Further manipulation at higher angles of β c1 = −6.2°, β c2 = 0°, and β c3 = 6.4° allows the focal point to reduce from ƒ b ≈ 525 mm to ƒ c ≈ 263 mm; ( d ) By controlling the arrayed prisms ( β d1 = −7.3°, β d2 = −4.0°, and β d3 = 0°) non-symmetrically, spatial focal tuning has been achieved in both longitudinal and lateral directions at ƒ d ≈ 444 mm and ƒ lat = 30 mm (reprinted from [ 21 ] with the permission).…”

Electrowetting actuated liquid prism with large steering angle based on additional gravitational effects

“…However, the reported liquid prism has small aperture size (about hundreds of microns). A beam deflector based on electrowetting is proposed, which has the merits of big size and large tilt angle (~30°). However, the steering angle is 12° (−6° to +6°) and it still can be improved.…”