Electrical Impedance Analysis of Carbon Nanotube-Polyelectrolyte Thin Film Strain Sensors

Single wall carbon nanotubes (SWNT) are an impressive material at the center of the nanotechnology revolution; in particular, SWNT posses a unique array of physical properties including high stiffness and good chemical reactivity. SWNTs are explored for inclusion in polymer matrices to produce thin films with electrical properties that exhibit sensitivity to strain loading. A layer-by-layer (LbL) fabrication procedure is detailed for the manufacture of free-standing thin films defined by interdigitated phase homogeneity and high strength. A characteristic feature of the proposed SWNT-polyelectrolyte (SWNT-PE) thin films is that nano-scale constituents can be deliberately varied to attain desired macroscopic electromechanical properties. Concentrations of SWNT and PE are varied to yield thin film strain sensors with high gage factors. SWNT-PE thin film strain sensors are patterned upon substrates as inductive coil antennas that can be wirelessly interrogated by a remote wireless reader. To fully characterize the wireless read-out mechanism of the patterned SWNT-PE antennas, electrical impedance spectroscopic (EIS) analysis of the thin films is performed.