Percolation-Tunneling Synergistic Coupling: A Composite Design Strategy for High-Sensitivity Wide-Range Flexible Pressure Sensors

Flexible pressure sensors have attracted widespread interest due to their enormous potential for applications. At present, research on these sensors can achieve low pressure, high sensitivity, or a wide detection range. However, the sensitivity in high-pressure areas (150–300 kPa) typically decays to <0.1 kPa^–1, making it difficult to maintain high sensitivity under high pressure. Herein, this study proposes a flexible pressure sensor based on a percolation-tunneling synergistic coupling mechanism. The sensor comprises PVA/H₃PO₄/CNTs ionic hydrogel film (PHCF) and a PVDF nanofiber film. The top and bottom layers of the sensor consist of PHCF. Under pressure, the deformation of PHCF will lead to the redistribution of carbon nanotubes, resulting in an increase in the number of seepage paths. The middle layer is a PVDF nanofiber film. On the one hand, it acts as an insulating layer, reducing the initial contact area between PHCF, thus generating a lower and more stable initial current. On the other hand, due to its piezoelectric effect, it reduces the tunneling barrier height and improves the tunneling probability of electrons in PHCF through the PVDF layer. Benefiting from the coupling of the PHCF permeation network and PVDF modulated tunnel barrier, the sensor achieved a high sensitivity of 178.4 kPa^–1 at low pressure (0–10 kPa). It also provides a wide measurement range of 0–300 kPa and a sensitivity of up to 20.2 kPa^–1 under full pressure. Sensors achieve the unity of low-cost production, ease of manufacturing, and high detection performance. The device exhibits a rapid response time of 97 ms along with an 85 ms relaxation time and excellent cyclic pressure stability (3000 cycles). Furthermore, the sensor validates its feasibility in monitoring human physiological signals and serves as an effective platform for Morse code signal transmission. These outstanding performances highlight the enormous potential of the sensor in pressure monitoring applications.