fig3

Figure 3. Electrical properties of the respiratory triboelectric sensors. (A) Schematic diagram of the working mechanism; (B) Output voltages comparison and (C) Signal output curves of sensors with different plasma treatment times under an external pressure of 1 kPa; (D) Simulation mappings of surface potential distribution during contact-separation process for smooth-surfaced and rough-surfaced fibers; (E) and (F) Output curves of the respiratory triboelectric sensors under different pressures at a constant frequency of 2 Hz and under different frequencies at a constant pressure of 1 kPa, respectively; (G) Response and recovery times of the respiratory triboelectric sensor; (H) Durability test of the respiratory triboelectric sensor under a pressure of 1 kPa. PVDF: Polyvinylidene fluoride.