Geometry-Tunable Stretchability and Piezoresistive Response in Growth-Programmable In-Plane Silicon Nanowire Springs

Silicon nanowires (SiNWs) are highly effective piezoresistive channels for strain sensing, yet achieving stretchable SiNWs remains challenging because their intrinsic brittleness imposes a trade-off between tensile deformability and piezoresistive sensitivity. Here, we establish a growth-level geometry programming strategy that enables spring-shaped SiNWs with precisely defined architectures. By modulating spring amplitude, geometry-dependent tensile stretchability and piezoresistive response are achieved. Mechanical and electrical analyses reveal that geometry governs stress transfer into the SiNW backbone by redistributing deformation between spring unfolding and axial strain, thereby regulating the trade-off between stretchability and sensitivity. Small-amplitude springs exhibit a gauge factor of 5.1 with tensile strains up to 20%, whereas large-amplitude springs sustain 50% strain with a gauge factor of 2.1. This work demonstrates the potential of growth-programmed geometry engineering for tailoring electromechanical coupling in stretchable SiNWs.