3D Printing of Spherical Crown Friction Electric Self-powered Compressive Strain Sensing Structure and Its Application

This study designs a spherical crown self-powered compressive strain sensing structure to meet the demand for flexible wearable devices capable of compressive strain sensing. Nylon cloth and silicone serve as positive and negative friction materials, respectively, based on the principle of frictional electricity generation of the Triboelectric Nanogenerator (TENG). The design strategy is utilized to achieve variable compression in the friction contact area by employing heterogeneous silicone materials. The principle of self-powered compressive strain sensing is elucidated. Three different mass ratios of printing ink composition materials are developed. The multi-nozzle silicone direct writing 3D printing technology is employed to fabricate this self-powered compressive strain sensing structure. The microscopic morphology of the spherical crown friction structure section is analyzed using a scanning electron microscope. The impact of spherical crown size and compressive strain on the output electrical performance of the sensing structure is investigated through a specially developed compressive motion experimental device. The experimental results indicated that the output signal of the maximum compressive strain increases with the height of the supporting spherical crown. Moreover, the open-circuit voltage, short-circuit transferred charge, and short-circuit current all positively correlate with the compressive strain. As the compressive strain increases from 7% to 35%, the peak open-circuit voltage escalates from 5.3 V to 22.2 V. Concurrently, the sensing structure exhibits robust durability and stability. Ultimately, a self-powered sensing insole utilizing the spherical crown compressive strain sensing structure is designed, demonstrating effective application in monitoring gait and plantar pressure distribution. This study offers novel insights and approaches for the design and production of multi-material wearable flexible self-powered compressive strain sensing structures.