Design and Performance Enhancement of a Flexible Tactile Sensor with Skin-Inspired Multilayer Architecture and Hair-Mimicking Microcolumn Embedding

Accurate and decoupled detection of normal and shear forces is essential for next-generation tactile systems but remains challenging due to structural limitations and material constraints in existing flexible sensors. To address this, a biomimetic trilayer flexible sensor that integrates a rigid microcolumn and dual piezoresistive layers of liquid metal is designed, enabling simultaneous detection of pressure and shear strain. A scalable spray-coating process is developed using ethanol- and iron-modified liquid metal ink, which improves adhesion to PDMS and prevents nozzle corrosion. Guided by finite element simulations (ABAQUS controlled via Python), the sensor geometry is optimized for enhanced directional decoupling. Experimental results demonstrate excellent linearity (R² > 0.996) across a wide pressure range (70.77–533.61 kPa), rapid response, and strong durability under repeated loading. This work provides a robust and scalable approach for fabricating high-performance, multimodal flexible sensors with broad potential in robotic e-skins, industrial inspection, and interactive electronics.