Flexible 3-D Pressure Sensor Based on PEI-Decorated Porous Sponge for Human Physiological Monitoring

Flexible 3D pressure sensors are widely used in smart robotics, human-machine interfaces, wearable devices, etc., which are generally prepared by combining conductive materials and elastic matrix, forming a conductive network. However, the uncontrollable combination process often leads to fragile and uneven interfaces. Here we introduce polyetherimide (PEI) into the porous sponge as an intermediate layer between the conductive material and polymer skeleton, providing enhanced force of carbon nanotubes on fibers and improving uniform distribution of the conductive material. PEI-decorated sponges prepared by simple dip-coating method are compared with exclude ones, confirming the effects of PEI on sensor performance. Moreover, the PEI-decorated sponges are analyzed under different concentrations of carbon nanotubes. The results show that the sensor of 5 mg/ml carbon nantubes has ultrahigh sensitivity of 0.57 kPa<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> in the 0-20 kPa range and 1.34 kPa<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> in the 20-117 kPa range, fast response time of 160 ms, and outstanding stability over 8000 cycles. The prepared sensors perform well in measuring heartbeat, joint activity, and plantar pressure. It is thus concluded that the introduction of polymer adhesives into porous structure has provided a technical reference for human physiological monitoring.