Tailoring Piezoresistive Behavior of Compressive Strain Sensors by 3D-Printed Structure and Filler Dispersity

Flexible strain sensors are in high demand for wearable devices and smart healthcare applications. However, compressive strain sensors receive less attention than stretchable counterparts due to their limited sensitivity under compression. Emerging 3D printing technology enables precise control over cellular structures, offering a promising approach to enhance their sensing performance. This study investigates the effects of carbon nanotube (CNT) content, dispersion, and printed structural parameters on 3D-printed polydimethylsiloxane (PDMS)/CNT compressive sensors. Sensors fabricated with 3 wt% CNT ink, prepared via two-roll milling, exhibit a positive resistance change rate under compression, improving sensitivity. The resistance change rate further increases as the printed line spacing decreases and the number of layers increases. Significant variations in sensing behavior, such as resistance increase or decrease under strain, are observed and explained through a unified structural change model. The cyclability of sensors exhibiting different resistance responses is compared, demonstrating the reliability of the optimized sensors for human motion monitoring and spatial force detection. This work deepens the understanding of the piezoresistive behavior of 3D-printed compressive sensors and provides valuable guidance for their design, fabrication, and application.