Investigation on liquid medium integration for piezoelectric MEMS tunable liquid lenses

In this paper, the design, fabrication and evaluation of a novel piezoelectric MEMS varifocal liquid lens are presented. The device consists of a thin film PZT actuator integrated with a liquid lens, featuring a new design with a modified disk-shaped actuator that enhances the overall displacement range. The primary innovation lies in simplifying the assembly process between the liquid/soft lens and the piezoelectric actuator, eliminating the need for vacuum bonding. Two types of liquid/soft lens materials, ionic gel and silicone oil, were investigated in different integration configurations to find the most suitable method. Analytical calculations and FEM simulations were conducted to optimize the actuator's maximum displacement, which in turn maximizes the change in the device's focal length. The developed actuator achieved around 15 µm of static displacement under a 40 V DC applied voltage, which matched well with simulation results. The shifting of the focus was clearly observed through a microscope, with the focal length estimated to change from infinity to about 31.6 mm at 35 V DC.