Enhanced Strain-Dependent Electrical Resistance of Polyurethane Composites with Embedded Oxidized Multiwalled Carbon Nanotube Networks

Abstract

The effect of different chemical oxidation of multiwalled carbon nanotubes with H2O2, HNO3, and KMnO4on the change of electrical resistance of polyurethane composites with embedded oxidized nanotube networks subjected to elongation and bending has been studied. The testing has shown about twenty-fold increase in the electrical resistance for the composite prepared from KMnO4oxidized nanotubes in comparison to the composites prepared from the pristine and other oxidized nanotubes. The evaluated sensitivity of KMnO4treated composite in terms of the gauge factor increases with strain to nearly 175 at the strain 11%. This is a substantial increase, which ranks the composite prepared from KMnO4oxidized nanotubes among materials as strain gauges with the highest electromechanical sensitivity. The observed differences in electromechanical properties of the composites are discussed on basis of their structure which is examined by the measurements of Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscope. The possible practical use of the composites is demonstrated by monitoring of elbow joint flexion during two different physical exercises.

Multifunctional flexible and stretchable polyurethane/carbon nanotube strain sensor for human breath monitoring

“…Oxygen content (at %) measured by XPS determined the oxygen involving functional groups (C═O, C─O, O─C═O) in amount of 13.0 and 21.7% for pure and KMnO 4 treated CNTs. Further, the ratio of sp 3 /sp 2 carbon atoms was found to be 2.50 and 1.69 …”

“…Finally, a gesture‐based human‐machine interface was developer by the resistance change of glove‐mounted sensors while bending a finger . Another types of crack‐based sensor were demonstrated for example in previous studies . In another case, polymer/graphite sensor was capable to detect very soft human movements such as pulses, respiration rates, and throat vibration .…”

“…An excellent deformation capability compared to the traditional rigid metallic strain gauges and conductors predetermines them for new and beneficial applications. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] These composite materials are usually composed as two component systems using electrically conductive filler (nanowires 2 or metal particles, 3 but mainly carbon-based materials like carbon nanotubes [CNTs], [4][5][6][7][8][9] carbon nanofibers, 1 carbon black [CB], 10 graphite flakes, 11 graphite, 12 or graphene [GF] 13 ) dispersed in a polymeric matrix or superimposed on polymer-based support. The deformation of these polymer composite units results in a change in their electrical conductivity due to the piezoresistive properties of the CNT conductive network.…”

“…Finally, they also have other very perspective functional properties such as high sensitivity to deformation stimulus, reversibility of responses, durability, and detection capability over many cycles. These advantageous functional properties predestine them to be materials very asked for and required for arising areas of interests such as health monitoring, 12 human-friendly wearable interactive systems or human motion detection, 5,6,8,9,14 human-machine interfaces, 5,15 electronic skins, 4 smart fabrics, 15,16 soft and smart robotics, 14 or athletic training. 12 As straightforward examples of practical compositions, properties and applications of elastic polymer composite materials applied for mechanical strain detection can be summarized in the following paragraph.…”

“…5 Another types of crack-based sensor were demonstrated for example in previous studies. [6][7][8]17,18 In another case, polymer/graphite sensor was capable to detect very soft human movements such as pulses, respiration rates, and throat vibration. 12 In the next paper, polydimethylsiloxane (PDMS)-based composites were fabricated by using a solution mixing-casting molding method incorporating into matrix hybrid CNTs/CB nanofillers.…”