Strain redistribution for achieving wide-range and high-sensitivity monitoring of natural rubber-based sensors

Strain sensors with high sensitivity and wide detection range are essential for meeting diverse applications, such as precisely monitoring the movement of patients with bone defects during rehabilitation. However, extending the sensing range without compromising sensitivity, particularly for small strains, remains a significant challenge for flexible sensors. Here, a strain redistribution strategy was employed to achieve wide-range and highsensitivity monitoring of natural rubber (NR)-based sensors. A rectangular NR-based sensor was initially developed using the swelling-infiltration method, demonstrating a broad strain range but low sensitivity. The introduction of V-notches on both sides of the sensor resulted in significant local strain enhancement, substantially improving sensitivity but significantly reducing the sensing range. For example, the gauge factor (GF) increased from 4.2 to 28.4 at 20 % strain, while the sensing range decreased from 400.5 % to 71.4 %. Furthermore, O-notches were integrated into the NR-based sensor to facilitate strain redistribution. A welldesigned O-notch enhanced the sensing range by 40 % without sacrificing small-strain sensitivity. Additionally, the NR-based sensor with strain redistribution demonstrated a low detection limit (0.1 %), excellent cyclic stability, and biocompatibility, making it highly effective for detecting large and small deformations in the human body.