Facile and Scalable Fabrication of Micro-Dome Structure Array Based on Liquid Metal and its Application for High-Performance Flexible Pressure Sensors

Artificial somatosensory systems in humanoid robots are essential to building physical interactions with objects and environments. Specifically, bioinspired sensors mimicking dome-like wrinkled structures underneath the epidermis play an important role in achieving high sensitivity and wide-range pressure detection. This study introduces a novel fabrication technique to create a high-resolution and high-density micro-dome structure array based on liquid metal by utilizing hybrid lithography (photolithography-soft lithography) and the selective wetting characteristic of the liquid metal. The micro-dome structures based on liquid metal can be scaled from sub-um to mm and formed over 70,000 patterns in a 1 area with a diameter of 10 with 10 spacing. The fabricated micro-dome structure arrays were utilized to create deformable and micro-dome-structured pressure-sensitive layers for flexible capacitive pressure sensors. The pressure sensing performance of the fabricated pressure sensors with different diameters and spacing of the dome structures was conducted and verified through simulations and experiments. The design parameters with larger spacing and smaller diameters showed high sensitivity in a small pressure range <10 kPa. Furthermore, the flexible pressure sensors maintained consistent performance under repetitive mechanical testing. The proposed fabrication technique allows the creation of multiscale micropatterns designed to meet specific performance requirements, such as sensor size, sensitivity, and sensing range. The proposed fabrication technique is expected to be applied to tailored pressure sensors requiring various performance levels.