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Design and fabrication of tri-liquid bifrustum–cylinder electrowetting lens

Year: 2026
Type: article
Abstract: Electrowetting adaptive focal-tunable lenses have attracted extensive attention in micro-optics owing to facile fabrication and fast response, and extending their focal length tuning range remains a critical challenge. This paper proposes and fabricates a tri-liquid bifrustum-cylinder electrowetting lens (TL-BEL). The lens adopts a symmetric bifrustum-cylinder cavity filled with three immiscible liquid layers, including two outer conductive liquids and one intermediate insulating liquid. The structure forms two liquid-liquid interfaces, whose curvatures can be separately modulated via two independent electrodes based on the electrowetting effect. Compared with conventional dual-liquid cylindrical electrowetting lenses, the TL-BEL achieves two distinct improvements. First, the extra tunable liquid-liquid interface provides an additional degree of freedom to extend the overall focal length tuning range. Second, the inclined cavity wall enables directional modulation of optical power. Specifically, a positive cone angle of the frustum enhances negative focal length tuning, while a negative cone angle enhances the positive regulation. This mechanism is verified by theoretical derivation and numerical simulation. A TL-BEL prototype with a 24° cone angle is fabricated and tested, which exhibits good reversibility and repeatability under driving voltages ranging from 0 V to 80 V. By adjusting the applied voltages, continuous focal length tuning ranging from -95.59 mm to -20.73 mm can be achieved, which agrees well with the numerical simulations. Benefiting from the compact tri-liquid architecture and directional focal tunability, the proposed lens is promising for applications in various miniature imaging systems.
DOI: 10.1364/oe.616103
Language: English
Open Access status: gold
Estimated APC paid: $2,270
OpenAlex ID: W7221723445
FWCI:
Cites: 28
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Related to: 10