Flexible Piezoresistive Pressure Sensor Using Wrinkled Carbon Nanotube Thin Films for Human Physiological Signals

Highly sensitive and flexible components are essential for applications in wearable electronics. Using low-cost and rapid prototyping methods, piezoresistive pressure sensors are fabricated using shrink-film, a shape memory polymer that retracts upon heat, to introduce wrinkling in carbon nanotube thin films, which improves both elasticity and pressure sensitivity. The wrinkles not only provide strain relief, but it also improves pressure sensitivity by 12 800 fold with a response time of less than 20 ms. The improved sensitivity is due to the surface roughness of the wrinkles. When two wrinkled electrodes are coupled together, the number of electrical contact points changes upon actuation thereby changing the electrical resistivity. This study then demonstrates wearable applications, such as pulsatile blood flow monitoring and voice detection using these sensitive pressure sensors.