Flexible and high-performance piezoresistive strain sensors based on carbon nanoparticles@polyurethane sponges

Abstract

In this work, flexible and high-performance piezoresistive strain sensors were fabricated by simple layer-by-layer electrostatic self-assembly of carbon nanoparticles on commercial polyurethane (PU) sponges. It was shown that the sponge-based strain sensors exhibited obviously positive and negative piezoresistive characteristics under tensile and compressive strains, respectively. The alternate assembly of carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) contributed to the construction of a more complete conductive network and significantly improved the sensing performance of the sensor due to the synergistic effect between CNTs and GNPs. Compared with the CNT@PU and CNT/GNP@PU sponge strain sensors, the CNT/GNP/CNT@PU sensor had a larger strain detection range and higher linearity. Besides, the CNT/GNP/CNT@PU sponge strain sensor showed high sensitivity (GF = 43,000 at 60% tensile strain and GF = − 1.1 at 50% compressive strain), responsive capability to very small strain (0.05%) and outstanding stability during 3000 loading cycles. Due to its excellent sensing performance, the CNT/GNP/CNT@PU sensor enabled monitoring of various physiological activities, including finger movements, wrist bending and walking etc. In addition, a 5 × 5 sensor array based on the sponge-based strain sensor was prepared to achieve accurate identification of weight distribution. This study provides valuable information for the development of flexible strain sensors with high-performance and low-cost.

High-Performance Foam-Shaped Strain Sensor Based on Carbon Nanotubes and Ti3C2Tx MXene for the Monitoring of Human Activities

“…From the brightness of the LEDs, the change of the electric resistance of the foam could be clearly distinguished with the naked eye (Figure e). Moreover, the electric resistance of the foam also changed under repeated torsional and bending deformation (Figure S9 in the Supporting Information), suggesting that this foam could also be used for the sensing of various strains, which is usually difficult to achieve with film-shaped strain sensors . Therefore, our foam-shaped strain sensor may become a promising candidate in the sensing of human body motions, in which various types of strain normally coexist.…”

“…The obtained sensor can detect a strain up to 50–60% with a gauge factor (GF, ratio of the resistance responsivity to applied strain) of >1000. Although many film-shaped strain sensors have been reported with large sensing ranges, , they are usually only sensitive to tensile strains, limiting their applications in many scenarios …”

Strain‐sensing behavior of flexible polypropylene/poly(ethylene‐co‐octene)/multiwalled carbon nanotube nanocomposites under cyclic tensile deformation

“…This is generally ascribed to the evolution of conductive networks under strain and relaxation. [28][29][30] It is often put forward that the structural evolution of CPCs morphology has a significant effect on the electrical response of conductive networks. Elucidating its relevance in electricity-mechanical properties for CPCs is of great significance for effectively designing and expanding the application of these composites.…”

An electric‐driven variable stiffness morphing skin: Preparation and properties

“…[ 20 ] When multi‐component fillers are used, a synergistic effect between the fillers helps to improve the electrical properties of the material. [ 21 ] In the polyurethane matrix (TPU), CNT and silver nanoparticles (AgNPs) were added as conductive fillers, the introduction of AgNPs reduced the interaction between adjacent CNT (entanglement potential), and the resistivity of CNT:AgNPs (5:1)/TPU was reduced by 2.58 times, which compared with CNT/TPU. [ 22 ] Also, the electrical properties of the polymer could be affected by the conductive network structure, [ 23 ] the performance of the separated conductive network is better than that of the dispersed conductive network.…”