Optimization Process of PCL/TPU@MWCNTs Fiber Composites for Flexible Piezoresistive Sensors and Application in Hand Movements Perception

This study outlines the optimization process for a polycaprolactone (PCL)/polyurethane (TPU)@multiwalled carbon nanotubes (MWCNTs) fiber composite, designed explicitly for flexible piezoresistive sensors. The PCL/TPU fiber membrane prepared by electrospinning technology was used as the substrate. Functionalized MWCNTs, serving as exogenous conductive particles, were deposited on the membrane via vacuum filtration, thereby preparing the PCL/TPU@MWCNTs fiber composite. This study investigated the morphological characteristics, hydrophobicity, mechanical properties, and conductivity of the PCL/TPU@MWCNTs fiber composite. The aim was to determine suitable preparation parameters for flexible pressure sensors ideal for outdoor and medical applications. The test results indicated that the membrane spun at 28 kV and a spinning distance of 20 cm exhibited optimal mechanical properties. With a filtration volume of 7.5 mL, the MWCNTs in the membrane were uniformly distributed, with a thickness of 0.05 ± 0.01 mm, a water contact angle of 131°, a tensile strength of 14 MPa, an elongation at break of 32.4%, and a conductivity of 1.74 × 10^-4 S/m. The prepared sensor exhibited sensitivities of 1.86 kPa^-1 over 0-34 and 1.14 kPa^-1 over 35-75 kPa, with rise and fall response times of 9.41 and 10.89 ms, respectively. The sensor measured an average normalized peak output of 10.7108 (Δ<i>R</i>/<i>R</i> ₀%) for the index finger across 200 bending/straightening cycles, with a standard deviation of 0.02249. Furthermore, in tests involving unscrewing a bottle cap with two fingers, load pressure pulse patterns were successfully recognized over the 0-150 Hz frequency range. This preparation method demonstrates advantages in action recognition at high frequencies and aids precise control and optimization of finger movements.