Structurally Designed Hydrogel-based Pressure Sensors for Wearable Sensing

In this paper, 3D printing is utilized to create a hydrogel with a gradient hierarchical structure, which is employed in the assembly of flexible pressure sensors. Conductive hydrogel with 3D printing function enriches the selection and structural design of traditional sensing layers. To boost sensor performance, a hierarchical microstructure has been adopted, achieving dual improvements in sensitivity and sensing range. Additionally, gradient structures within the hydrogel further enhance sensitivity across a wide pressure range. Specifically, the capacitive pressure sensor exhibits sensitivity approximately 9 times higher (0.043 kPa ^-1 ) than conventional hydrogel-based sensors with planar structure (0.0048 kPa ^-1 ). The linear pressure range with high sensitivity expands roughly threefold to approximately ~338 kPa, which is equally effective for resistive pressure sensors. Furthermore, when the hydrogel-based sensor is encapsulated in polydimethylsiloxane (PDMS), it shows excellent rapid responsiveness and stability during 1000 compression/release cycles at ~800 kPa. This resilience makes it suitable for various applications, including monitoring human joint movements, capturing facial expressions, and detecting weak pulse vibrations. In summary, the structured hydrogel has significant potential for future flexible electronic applications.