Thin and Flexible Carbon Nanotube-Based Pressure Sensors with Ultra-wide Sensing Range

• Published in: ACS sensors Vol. 3; no. 7; pp. 1276 - 1282
• Main Authors: Doshi, Sagar M., Thostenson, Erik T.
• Format: Journal Article
• Language: English
• Published: 11.07.2018
• ISSN: 2379-3694
• DOI: 10.1021/acssensors.8b00378

A scalable electrophoretic deposition (EPD) approach is used to create novel thin, flexible and lightweight carbon nanotube-based textile pressure sensors. The pressure sensors can be produced using an extensive variety of natural and synthetic fibers. These piezoresistive sensors are sensitive to pressures ranging from the tactile range (< 10 kPa), in the body weight range (~ 500 kPa), and very high pressures (~40 MPa). The EPD technique enables the creation of a uniform carbon nanotube based nanocomposite coating, in the range of 250–750 nm thick, of polyethyleneimine (PEI) functionalized carbon nanotubes on non-conductive fibers. In this work, non-woven aramid fibers are coated by EPD onto a backing electrode followed by film formation onto the fibers creating a conductive network. The electrically conductive nanocomposite coating is firmly bonded to the fiber surface and shows piezoresistive electrical/mechanical coupling. The pressure sensor displays a large in-plane change in electrical conductivity with applied out-of-plane pressure. In-plane conductivity change results from fiber/fiber contact as well as the formation of a sponge-like piezoresistive nanocomposite “interphase” between the fibers. The resilience of the nanocomposite interphase enables sensing of high pressures without permanent changes to the sensor response, showing high repeatability. Carbon nanotubes (CNT) functionalized with polyethyleneimine (PEI) are deposited on aramid fibers using an innovative and scalable electrophoretic deposition (EPD) method. The PEI-CNT forms an electrically conductive and mechanically resilient nanocomposite coating, which enables piezoresistive pressure sensing in tactile as well as high pressure range with potential applications in smart textiles and wearable sensors for humans and e skins for robots.