Pressure Sensitive Sensors Based on Carbon Nanotubes, Graphene, and Its Composites

Abstract

Carbon nanotubes (CNTs) and graphene have attracted a great deal of interest due to their outstanding mechanical, optical, electrical, and structural properties. Most of the scientists and researchers have investigated the optical and electrical properties of these materials. However, due to unique electromechanical properties of these materials, it is required to explore the piezoresistive properties of bulk nanostructured CNTs, graphene, and CNT-graphene composites. We investigated and compared the sensitivities and piezoresistive properties of sandwich-type pure CNT, pure graphene, and CNT-graphene composite pressure sensors. For all the samples, increase in pressure from 0 to 0.183 kNm −2 results in a decrease in the impedance and direct current (DC) resistance. Sensitivity and percentage decrease in resistance and impedance of CNT-graphene composite were lower than pure CNT while being higher than pure graphene based sample. Moreover, under the same external applied pressure, the sensitivity and percentage decrease in impedance for pure CNT, pure graphene, and CNT-graphene composite were smaller than the corresponding sensitivity and percentage decrease in resistance. The achieved experimental results of the composite sample were compared with simulated results which exhibit reasonable agreement with each other. The deviations of simulated resistance-pressure and impedancepressure curves from experimental graphs were 0.029% and 0.105%, respectively.

Recent Progress on Flexible Capacitive Pressure Sensors: From Design and Materials to Applications

“…ITO is mechanically rigid in nature and loses its mechanical properties after multiple sensing, bending, and folding operations. [ 31,33,34 ] Nanomaterials such as graphene, [ 34–36 ] nanotubes, [ 32,35 ] nanowires [ 37,38 ] are still being explored for designing highly sensitive flexible electrodes for capacitive pressure sensors, however, their basic physical properties such as surface uniformity and conductivity are limited and lack the physical properties of thin film metallic and polymeric electrodes. [ 39–43 ] Thus, these nanomaterials are usually sandwiched between two thin films when utilized as electrodes.…”

“…[ 39–43 ] Thus, these nanomaterials are usually sandwiched between two thin films when utilized as electrodes. [ 32,34–38 ] B. U. Hwang et al presented a composite electrode based flexible capacitive pressure sensor in which the top electrode is based on PEDOT:PSS/EMIM‐TCB (poly‐(3,4‐ethylene‐dioxy‐thiophene):poly‐(styrene‐sulfonate)/1‐ethyl‐3‐methyl‐imidazolium tetracyano‐borate), which is piezoresistive in nature while GIG [Au‐ITO‐AU] is chosen as bottom electrode. [ 40 ] The effect of the aspect ratio on cantilever capacitive pressure sensors is analyzed using metal coated polymer as sensing electrode.…”

Elastic layered rubber-graphene composite fabricated by rubbing-in technology for the multi-functional sensors

“…In another study, we described the semitransparent thermo-electric cells based on the bismuth telluride and graphene composite. Pressure sensitive sensors based on carbon nanotubes, graphene, and its composites were investigated in [14]. Flexible impedance and capacitive tensile load sensor based on CNT composite was investigated in [15] and flexible resistive tensile load cells based on MWCNT/rubber composites was investigated in [16].…”

Proof of Concept: Pressure Sensor for Tracking of Infant-Mother Kangaroo Care Durations

“…The problem of flexibility was encountered in the design of smart skins where having a rigid material would make it difficult to get a measurement, such as heart rate on a flexible or curved surface [7]. In addition, producing pressure sensors with CNT or CNT composite materials increases cost effectiveness [8]. Also, CNT shows little change in conductivity between -20 and 80 °C [9].…”