Multi-walled carbon nanotubes/silicone conductive foams and their piezoresistive behaviors

A Comprehensive Review on Carbon-Based Polymer Nanocomposite Foams as Electromagnetic Interference Shields and Piezoresistive Sensors

“…Cellular piezoresistive sensors (CPSs), in which their electrical resistivity changes upon inducing mechanical deformation to unstretchable piezoresistive sensors, are one of the pioneer materials in sensor applications . These materials have drawn outstanding attention due to their magnificent electrical properties in widespread applications consisting of fluid power that requires high-resolution electronic measurement of pressure, wearable electronic devices to monitor human motions, , health care monitoring devices, , flexible tactual sensors, electronic skins, biochemical systems, monitoring concrete structures of buildings and robotic devices, and so forth. Different parameters should be considered for evaluating the performance of such sensors.…”

“…These factors are homogeneity and interconnectivity of porous structure, ,, size and distribution of cells, and cell wall thickness, ,,, and the orientation and dispersion of the nanoparticles at cell walls in the cellular morphology and loading of nanoparticles ,, are other vital factors especially for nanocomposite foams. It is worth noting that external pressure leads to collapse of voids in the foam structure, which results in increasing the nearness of the nanoparticles, ,, despite which the composites saw an improvement in piezoresistivity behavior. In addition, the reorientation of nanoparticles in this cellular media could influence the interconnectivity between the conductive nanoparticles.…”

“…As well as decreasing elastic modulus and density, distribution and orientation of MWCNTs were increased, which results in improving the piezoresistivity of the CPS. It was found that the MWCNTs achieved high orientation perpendicular to the compressive strain and high interconnectivity while undergoing the external pressure . Moreover, Hsiao et al .…”

“…The type of foaming agent used in the foaming process has a significant effect on the properties and porosity of fabricated CPSs and their piezoresistivity. Guo et al 119 used different types of foaming agents to acquire various porous structures of multiwalled carbon nanotube (MWCNT)/silicone CPSs. Among different applied foaming agents, oxydibenzenesulfonyl hydrazide (OBSH) enabled higher porosity accompanied by a nonlinear behavior that unambiguously confirmed higher affinity with nonpolar rubber matrix due to its partial molecular polarity.…”

“…It was found that the MWCNTs achieved high orientation perpendicular to the compressive strain and high interconnectivity while undergoing the external pressure. 119 Moreover, Hsiao et al 118 revealed that the foaming agent concentration in fabrication of CPSs is a critical parameter in the performance of pressure/strain sensing. Due to generating more bubbles, increasing the foaming agent content resulted in decreasing pore sizes.…”