Abstract
Accurate shape sensing requires simultaneous quantification of bending angle (φ) and bending direction (θ). Yet existing bending sensors remain confined to uniaxial or discretized modes, relying on tedious, non-generalizable calibration procedures. Here, we present a snowflake-shaped omnidirectional bending sensor that achieves complete and linear decoupling of φ and θ through a three-fold rotationally symmetric arrangement of strain-sensitive resistors. By harnessing geometric symmetry as a physical prior, we establish a closed-form analytical model and signal projection framework that transform calibration from an empirical process into a simple, quantitative, universal procedure. The sensor is compatible with standard flexible printed circuit board (FPCB) fabrication on polyimide (PI) and polyethylene terephthalate (PET) substrates, ensuring scalability and integration. We demonstrate real-time reconstruction of multidirectional surface deformation and in situ correction of ultrasound imaging artifacts during bending. This symmetry-guided approach redefines the design principles of deformation sensing, providing a general platform for dynamic shape reconstruction and opening avenues for self-adaptive and self-aware electronic systems.