Investigation Of Piezoresistive TPU/MWNT Oriented Micronano Fibers

As a mechano-receptive sensing system, haircell receptors widely exist in organisms. These kind of receptors are able to respond to flow in the air or water, vibration of environment, touch, acoustic vibration and gravitation. As the natural haircell receptors have the properties of wide range of applications, sensitive detection capability, and tiny size, the research of artificial hair sensor to simulate the natural haircell sensing system has attracted much attention. The purpose of this paper is focused to fabricate artificial haircell sensor with high length diameter ratio, flexibility and outstanding piezoresistive properties.The TPU/MWNT composite oriented micronano fibers have been prepared by electrostatic spinning technology with the use of thermoplastic polyurethane elastomer (TPU) and multi-walled carbon nanotubes (MWNTs). Pair of parallel plate electrodes have been used to realize the directional distribution of fibers and TPU/MWNT composite membranes have also been fabricated for comparison experiment. Scanning electron microscope (SEM) and transmission electron microscope (TEM) have been employed to analyze the distribution pattern of MWNTs in TPU. It is clearly showed that MWNTs are along with the axial direction in fibers and randomly distributed in membranes. Different distribution patterns which influences the piezoresistive properties have been discussed.A test bench has been designed to measure fiber conductivity and piezoresistive properties. Through experimental and theoretical methods, the percolation threshold and the relationship between resistance and tensile strain have been abtained. The mechanism of piezoresistive effect has been explained and the ratio of MWNTs and TPU for the best sensitivity is achieved.Finnaly, the parameters that may affect the resistance of TPU/MWNT composite consisted by oriented micronano fibers in tensile status have been analyzed, such as the change of microstructures, volume ratio of conductive particles, and distributed angles of MWNTs, which lead us to conclude that volume ratio of conductive particles is the main reason for the variation of resistance. A theoretical calculation model which is able to predict the change of resistance with strain has also been proposed.