Fig. 7
Performance evaluation of the fabricated pressure sensor: a measured relative change in resistance as a function of applied pressure in which two distinct regions were identified, resulting in sensitivities of 0.06 kPa−1 and 0.63 kPa−1 for the pressure ranges of 0 kPa to 3.5 kPa and 3.5 kPa to 6.8 kPa, respectively, b the relative change in resistance in response to 1000 cycles of loading with 5.1 kPa and 3.5 kPa, c the response delay time and relaxation time of the sensor when 6 kPa was applied and removed in a speed that simulates the infant’s natural NNS (peak pressure reached within 0.25 s), d the noise level in resistance of the sensor when the sensor was relaxed immediately after a pressure load application, which was used to calculate the sensor’s minimum measurable pressure as 2.47 Pa, e the hysteresis curves of 5 consecutive cycles of 4 kPa loading, and f the hysteresis curves under 4 kPa, 6 kPa and 8 kPa pressure