Eco-Friendly Multi-Walled Carbon-Based Nanotube (MWCNT)/Chitosan Composite As Conductive Ink For Printed Electronics

Abstract

The implementation of printed electronics is emerging as way forward for wearable application because of its flexibility, low-cost fabrication and reproducibility. Selection of conductive ink composition is crucial in printed electronics where it consists of conductive fillers, polymer binder, solvent and additives. Multiwalled carbon nanotubes (MWCNT) have been widely used as conductive filler as it has high electrical conductivity and has excellent mechanical properties. However, the involvement of synthetic binders such as polyvinyl chloride (PVC) in the synthesis of conductive composite ink will cause health and environmental issues because of its high toxicity and poor biocompatibility. Hence, the incorporation of biopolymer binder such as chitosan (CS) is used to enhance the conductive ink for printed electronics without risking human and environmental health. CS is a biopolymer which provides an alternative solution as eco-friendly binder due to its biodegradability, high tensile strength, nontoxic and environmental-friendly. However, limited previous work reported on the effect of different weightage of biopolymer binder and MWCNT filler specifically for screen printing requirement in printed electronics. Hence, the objective of this study is to investigate the effect of MWCNT filler dispersion on the performance of printed ink. The MWCNT/CS composite inks were synthesized at different weightages of CS polymer binder and MWCNT filler. Material characterization which includes surface morphology, chemical bonds, viscosity and conductivity were analyzed. Screen printing method was chosen as the fabrication technique on different types of substrates. Electromechanical test was conducted to analyze on the change of resistance of the printed ink on polymer substrate. Rheological properties of MWCNT/CS composite ink recorded the highest viscosity at 1.50 Pa.s and behaved as non-Newtonian fluid with shear thinning characteristic. Homogenous dispersion and proper disentanglement of MWCNT fillers within CS polymer was depicted through surface morphology analysis. Raman and FTIR analysis illustrated that MWCNT was successfully synthesized within CS polymer. The measured conductivity for printable MWCNT/CS composite ink was at 34.88 x 10-3 S/m which was comparable to previous work. The bending test proved that higher weightage of CS polymer binder will result to strong bond between CS and MWCNT and can prevent crack, resulting to flexible printed MWCNT/CS composite ink. Result shows that the optimum weightage of MWCNT/CS composite ink was found at 9 wt.% MWCNT/CS composite ink, having resistivity of 28.67 ?/m and viscosity of 1.24 Pa.s, which is in line with screen printing requirement. Plus, 9 wt.% MWCNT/CS composite ink was chosen as the optimum weight as it recorded good strain detection up to 50% compared to other ink weightage. Therefore, integration of CS as polymer binder for eco-friendly printable conductive ink provides promising solution for printed electronic applications.