Flexible\nStrain Sensors Fabricated by Meniscus-Guided\nPrinting of Carbon Nanotube–Polymer Composites

Abstract

Printed\nstrain sensors have promising potential as a human–machine\ninterface (HMI) for health-monitoring systems, human-friendly wearable\ninteractive systems, and smart robotics. Herein, flexible strain sensors\nbased on carbon nanotube (CNT)–polymer composites were fabricated\nby meniscus-guided printing using a CNT ink formulated from multiwall\nnanotubes (MWNTs) and polyvinylpyrrolidone (PVP); the ink was suitable\nfor micropatterning on nonflat (or curved) substrates and even three-dimensional\nstructures. The printed strain sensors exhibit a reproducible response\nto applied tensile and compressive strains, having gauge factors of\n13.07 under tensile strain and 12.87 under compressive strain; they\nalso exhibit high stability during ∼1500 bending cycles. Applied\nstrains induce a contact rearrangement of the MWNTs and a change in\nthe tunneling distance between them, resulting in a change in the\nresistance (Δ<i>R</i>/<i>R</i>₀) of the sensor. Printed MWNT–PVP sensors were used in gloves\nfor finger movement detection; these can be applied to human motion\ndetection and remote control of robotic equipment. Our results demonstrate\nthat meniscus-guided printing using CNT inks can produce highly flexible,\nsensitive, and inexpensive HMI devices.