Carbon black and boron nitride conductive fillers dispersed porous conductive polymer composite-based piezoresistive sensor for biomedical applications

Conductive nanofillers dispersed polymer composites (CPCs) are widely studied for applications of flexible resistance pressure sensor (fRPS). The piezoresistive effect in CPCs is appreciable when filler content is close to percolation threshold concentration (phi tc). Many CPCs require high filler concentration for percolation threshold resulting in increase of elastic modulus or mechanical stiffness. Further, nanofillers are relatively expensive. Hence reducing the elastic modulus and cost of total filler content is one of the main objectives of the fabrication of flexible and low-cost fRPS. It is reported that two different aspect ratios (AR) of conductive fillers will reduce phi tc in a CPC through bridge effect. Here heterogeneous binary (hybrid) conductive nanofillers, viz., 0D carbon black (CB) nanoparticles and 2D hexagonal boron nitride (hBN) nanosheets, dispersed on a porous polydimethylsiloxane (pPDMS) matrix has been used as piezoresistance material and evaluated its fRPS parameters and extended further for applications. pPDMS matrix has been prepared by hard template method using citric acid as pore forming agent. Crystal structure and morphology of both the fillers are confirmed by X-ray diffraction and electron microscope techniques. The piezoresistors with CB:hBN filler content at 3:1, 4:1, & 5:1 wt% show sensitivity of 0.21, 0.42, & 0.48 kPa-1, respectively. The piezoresistor with highest sensitivity shows linear output response in 0-5 kPa working range with excellent stable output in durability test. The high sensitive sensor is used in both pressure and strain sensing modes to measure human pulse profile, touch sensing, finger bending, wrist bending, vocal card motion. The sensor shows very good response. Thus the sensor may be useful for biomedical applications.