Abstract:
The demand and use of conductive nanomaterial-based stretchable and flexible multifunctional devices have been increasing due to their unique applications in many areas, such as detection of human body motions, soft robotics, human-machine interface, and localised heaters. However, it is a challenge to manufacture these devices through a cost-effective and environmentally friendly method with the assurance of good electrical conductivity. Several studies have been carried out to fabricate conductive natural fabrics using graphene, to make use of its electrical conductivity. However, the use of graphene can only improve the electrical conductivity of natural fibres to a certain extent. The current study involves the development of electronic devices based on biodegradable natural materials and graphene nanoplatelets (GNPs) through a simple and novel coating technique involving ultrasonication to obtain conductive natural fabrics. A systematic study on improving the electrical conductivity of natural fabrics was conducted by varying the proportions of graphene. Then, the conductive natural fabrics were fabricated by hybridising graphene with conducting polymers, polypyrrole (PPy) and polyaniline (PANI), and other carbon particles, such as carbon black (CB). The electrical conductivity was studied for the hybridised composites as well. Morphological analysis, thermal and mechanical characterisations were carried out on the produced samples. The conductive composites were incorporated into a flexible and stretchable elastomer (Ecoflex®) to be used as strain sensors. Electromechanical characterisations were carried out on the sensors and they were used to test different human body motions, including finger, wrist, elbow and knee movements. The results showed that the addition of a conducting polymer, such as PPy, expectedly increased the electrical conductivity in certain fabrics (for instance, cotton, with a conductivity of 1.7 S.cm-1). However, the addition of other conductive particles such as PANI, tend to have a negative effect on the conductivity. This was due to the presence of higher proportions of graphene when compared to PANI, in which the former created an insulating area between the conducting PANI domains. It was observed that the thermal stability improved with the addition of conductive particles and they showed excellent sensitivity and durability.