Microstructural Engineering of Flexible Sensors: From Uniaxial to Triaxial Force Detection

Flexible force sensors rely on soft elastomers and stretchable conductors to conform to curved surfaces and convert mechanical loads into electrical signals. However, the intrinsically nonlinear and coupled mechanical responses of soft materials make it difficult to simultaneously achieve high sensitivity, broad dynamic range, and long-term stability. In this Review, microstructural architecture is identified as a primary design variable governing force-to-electrical transduction beyond material composition alone. A unified structural framework is established to connect uniaxial force sensing and triaxial force sensing through the deliberate regulation of deformation modes and load-transfer pathways. Porous, micropatterned, and hierarchical structures are examined for their roles in amplifying and stabilizing pressure-induced responses in uniaxial sensing, whereas distributed arrays and multilayer heterogeneous designs are analyzed for their abilities to enable directional discrimination, signal reconstruction, and normal-shear force decoupling in triaxial sensing. By comparing structure-mediated behaviors across major transduction mechanisms, general design principles are identified for improving sensitivity, linearity, and force decoupling, while the growing integration of structural engineering with data-driven signal reconstruction is also highlighted. This perspective provides a rational foundation for the design of next-generation wearable electronics and robotic tactile systems.