Design and fabrication of a DLP-printed flexible wearable strain sensor based on solvent-free photopolymerizable resin

The rapid progress in robotics and materials science has driven the innovation of flexible sensors, leading to important developments in wearable technology. These smart sensors, capable of detecting mechanical stimuli such as pressure, deformation, humidity, temperature, and light, find many powerful applications in health, medicine, sports, soft robotics, prosthetics, and human-machine interaction. Here, this thesis explores the design, fabrication, and characterization of a flexible strain sensor based on DLP solvent-free acrylate resin with ion conductivity given by lithium chloride. Utilizing a 3D printing DLP process, various sensor configurations were produced and tested to evaluate their mechanical and electrical response. The sensible layer, electrodes, and shells were studied to determine the optimal setup. The device demonstrated good mechanical properties, as well as good electrical properties (gauge factor about 1.8) and stability when subjected to cyclic tensile tests and durability tests. The applicability of this device was evaluated through detecting different signals of the human body. The results demonstrated that the performance of these sensors could be a promising starting point for the development of stable, conductive, low-cost, and easily manufactured devices. The findings suggest that these innovative sensors can bridge the gap between rigid electronics and soft human tissues.