Abstract
Compact and entirely soft optics with tunable and adaptive properties drive the development of life‐like soft robotic systems. Yet, existing approaches are either slow, require rigid components, or use high operating voltages of several kilovolts. Here, soft focus‐tunable lenses are introduced, which operate at practical voltages, cover a high range of adjustable focal lengths, and feature response times in the milliseconds range. The nature‐inspired design comprises a liquid‐filled elastomeric lens membrane, which is inflated by zipping electroactive polymers to tune the focal length. An analytic description of the tunable lens supports optimized designs and accurate prediction of the lens characteristics. Focal length changes between 22 and 550 mm (numerical aperture 0.14–0.005) within 260 ms, equal in performance to human eyes, are demonstrated for a lens with 3 mm aperture radius, while applying voltages below 500 V. The presented model, design rules, and fabrication methods address central challenges of soft electrostatic actuators and optical systems, and pave the way toward autonomous bio‐inspired robots and machines.
Highlights
Compact and entirely soft optics with tunable and adaptive properties drive of an optical system with a single tunable lens represents a frugal approach with verthe development of life-like soft robotic systems
Lenses tuned by dielectric elastomer actuators (DEAs) overcome all these limitations, as they operate at high speeds, are electrically driven and soft.[1,13,14,15]
We introduce broadly applicable design rules, analytical models, and fabrication methods for soft tunable lenses based on zipping electroactive polymers (ZEAP) actuators operating at practical voltages
Summary
As the lens performance depends on various design parameters such as membrane thickness and actuator dimensions, we modeled the lenses analytically and numerically to predict the focus versus voltage characteristics. The connection of lens membrane and base keeps the membrane in a fixed position and allows homogenous inflation (and pressure) by the dielectric fluid Omitting this connection can lead to directional inflation of the membrane, which is beneficial for other applications that involve touch, such as buttons or brail displays.[21] Heat-sealing the electrodes in regular steps along the edge of the electrodes introduces specific starting points for zipping to improve the zipping homogeneity (we use this for all our lenses) and partially reduces the threshold voltage (Figure S3, Supporting Information). Our approach represents a major step towards low-voltage electroactive actuators, applicable to tunable optics, soft machines and robotics
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