Carbon Nanotube Coated Fabric-Based Thin and Flexible Pressure Sensors with Ultra-Wide Sensing Range

摘要

This research focuses on the development and validation of novel flexible piezoresistive sensors that can be integrated into functional fabrics and footwear. Formation of thin nanocomposite films of electrically conductive carbon nanotubes (CNTs) using a scalable electrophoretic deposition (EPD) technique enables the sensing functionality. Films in the range of 250 - 750 nm are created on a variety of natural (cotton, wool) and synthetic (aramid, spandex) fibers using the EPD process. In this research, non-woven aramid fabric with randomly oriented fibers are coated with carbon nanotubes and polyethyleneimine (PEI). The aramid fabric is placed in direct contact with an electrode and PEI functionalized CNTs deposited under a DC electric field. The nanocomposite film first forms on the backing electrode and continues to grow around the aramid fibers and uniformly coats fibers throughout the thickness of the fabric. The pressure sensor exhibits a large change in the in-plane electrical conductivity when out-of-plane pressure is applied. Formation of additional fiber-fiber contacts as well as the creation of sponge-like piezoresistive nanocomposite interphase between the fibers likely causes the in-plane electrical conductivity changes. The piezoresistive pressure sensors have an ultra-wide range of pressure sensing, from the tactile range (< 10 kPa) to body weight range (~500 kPa) and very high pressures (40 MPa). This wide sensing range enables applications in broad fields such as e-skin for robotics, human-computer interaction, biomedical devices and gait analysis. The sensors are integrated into footwear and preliminary tests conducted to explore applications in gait analysis and validate the sensor response using a treadmill instrumented with force sensors.