No abstract

Flexible pressure sensors have attracted significant attention owing to their broad applicability in wearable electronics and human–machine interfaces. However, it is still challenging to simultaneously achieve a broad sensing range and high linearity. Here, we present a reversed lattice structure (RLS) piezoresistive sensor obtained through a layer-level engineered additive infill structure via conventional fused deposition modeling three-dimensional (3D) printing. The optimized RLS piezoresistive sensor attained a pressure sensing range (0.03–1630 kPa) with high linearity (coefficient of determination, R 2 = 0.998) and sensitivity (1.26 kPa–1) due to the structurally enhanced compressibility and spontaneous transition of dominant sensing mechanism of the sensor. It also exhibited great mechanical/electrical durability and a rapid response/recovery time (170/70 ms). This remarkable performance enables the detection of various human motions over a broad spectrum, from pulse detection to human walking. Finally, a wearable electronic glove was developed to analyze the pressure distribution in various situations, thereby demonstrating its applicability in multipurpose wearable electronics.

This study presents capacitive-type inclinometers composed of flexible polymer pillars and dome-shaped roof frames that were manufactured using the three-dimensional (3D) printing method. Polylactic acid (PLA) filaments and acrylonitrile butadiene styrene (ABS) filaments were printed by the fused deposition modeling type 3D printer to fabricate the dome-shaped roof frames and the polymer curing molds, respectively. The operating principle of the inclinometer was to detect the change in capacitance between the helix-shaped electrode coiled around the polymer pillar and the built-in electrode in the roof frame. When the inclinometer was tilted, the polymer pillar was bent, and the physical distance between each electrode was changed with respect to the tilt angle and direction. Therefore, the tilt angles and directions were simultaneously estimated by distinguishing the capacitance and peak capacitance, respectively. The results of the experiments revealed that the inclinometer using the polymer pillar that was electrically connected to a standard weight and the roof frame with a roof angle of 45 • exhibited a higher sensitivity (1.391 pF at a tilt angle of 40 • ) compared to those using roof angles of 90 • and 135 • . This study supports the use of 3D printing technology for the facile manufacturing of inclinometers that can detect tilt angles and directions simultaneously, which is not achievable with conventional inclinometers.INDEX TERMS 3D printing, inclinometer, capacitive, polymer, rapid prototyping.