Varifocal liquid microlens in scaffold microstructures under electrothermal actuation

Liquid microlens (LML) has attracted wide attention due to their miniaturization, uniformities and easy integration in adaptive optical systems. However, optical aberration and simple varifocal imaging are still critical challenges for the broader application of LML. Inspired by the easy deformation of droplets trapped by micropillars, LML in scaffold microstructures are proposed. In this paper, we present a simple, low-cost and effective approach to fabricate LML in scaffold microstructures. Our LML consists of glycerol droplets trapped in hydrophobic NOA71 scaffold microstructures, which are imprinted onto an ITO glass substrate to enable electrothermal control of the LML imaging characteristics. The electrothermal control allows changing the shape of the LML spherical surface, thus making it possible to tune their focus, decrease their imaging aberration, and improve their imaging definition. The electrothermal actuator is obtained by applying a DC power with a voltage of 8.4 V and a current of 0.39 A onto the ITO glass. It is found that the imaging aberration of LML reduced by 6 times of initial state and the imaging definition of LML increased by 2.8 times of initial state on the DC power for 2 min. Thus, the LML in scaffold microstructures demonstrates the potential of the adjustable imaging performance in the development of integrated dynamical tunable optical devices.