Patterned Carbon Nanotube Sensing Skins for Strain Sensing

Abstract

Increasing demand for structural health monitoring (SHM) systems has accelerated technological innovation in a number of engineering arenas including in the development of new sensing technologies. Multifunctional materials that exhibit an ability to self-sense their response to external stimulus has shown promise for future SHM applications. One specific multifunctional material previously explored for SHM includes carbon nanotube (CNT)-polymer composite thin films deployed as sensing skins. While CNT-based sensing skins have shown great potential, their fabrication through layer-by-layer deposition has prevented fine geometric control of the skin features. The lithographic techniques commonly used in microelectromechanical systems (MEMS) could improve utilization of CNT-polymer sensing skins by allowing such films to be patterned into any desired geometric configuration. This study investigates the influence of geometric shape on the mechanical-electrical sensitivity of patterned CNT-polymer composite thin films. Layer-by-layer assembled single walled carbon nanotube (SWNT)-polymer thin films are patterned to varying sizes using a controlled lift-off process involving optically exposed sacrificial photoresist layers. Patterning quality is characterized using optical and scanning electron microscopy. The mechanical-electrical behavior of the various thin film geometries are analyzed through cyclic tensile load testing.