Hierarchical structural design towards stretchable strain sensors with ultra-high sensitivity and linearity

The increasing demands for flexible electronic devices have necessitated the development of sensors that possess remarkable sensitivity and linearity. However, conventional strain sensors encounter difficulties in simultaneously achieving above two desired characteristics, because a linear steep increase in resistance is difficult to realize due to the irreversible structural damage under tensile strain. Herein, a novel hierarchical interconnected structure with the external surface wrinkles and internal gradient pores was proposed to achieve extraordinary levels of sensitivity and high linearity in stretchable strain sensors. The nanoscale wrinkle spacing can be precisely controlled by hydrothermal activation mechanism. The bulk gradient porous structure was constructed through the manipulation of thermodynamic and kinetic behaviors of phase separation. Additionally, macroscopic curvatures on both sides of sensors were manipulated to achieve the anisotropy. The efficacy of various designs, quantized effective contributions of geometric configurations on the sensitivity and morphology evolution were discussed in depth. Due to the extraordinary sensitivity and anisotropy, our sensors have the capability to efficiently monitor alterations in both static and dynamic displacement, surface movement and two-dimensional strain signals, as well as predict variations in liquid level over time. Our approach provides a widely applicable, adaptable, scalable, and cost-effective method for achieving high-quality sensing capabilities.