Development of carbon ink for wearable sensors

Abstract

Conductive inks play an important role in the production of smart textiles. Among them, water based inks have drawn high attention because water is environmental friendly, harmless and easy-dried solvent. In practice, coffee ring effect is one of the problems which exists in water-based inks and influences the uniformity of the coating/printing process. Meanwhile, particle size, viscosity and surface tension of the ink are other key factors which should be adapted based on the substrate fabric, impregnation method and final application. This research aims at developing water-based carbon ink which is free from coffee ring effect for the construction of fine nonwoven polyester fabric based pressure sensors. Coffee ring effect leads to particles aggregation of functional particles among the edges of an ink drop during drying. Because of this, the functional particles are distributed non-uniformly on the substrate and lead to poor performance for the final application. This research works on the prevention of the coffee ring effect based on the Marangoni principle. During the research, ink was investigated with aspects to components, viscosity, surface tension and ink performance of the textile-based pressure sensor. In order to proof the elimination of coffee ring effect, scanning electron microscope (SEM) images were taken and analysed. The textile-based pressure sensors were constructed by applying inks on fine nonwoven polyester fabrics in order to evaluate performance of the ink. The sensors were produced with a sandwich structure and tested for capturing mechanical signals. The research results showed the elimination of coffee ring effect on the substrate textiles coated with the ink produced in this research. Textile-based nonwoven polyester pressure sensors produced in this research showed satisfactory properties. The sensors with carbon take-up rate of 70.6％ were able to achieve an average electronic resistance of 1817Ω and sensitivity of 9.16 KPa-1. The sensors were reliable with the limit of 400 compression cyclic tests within its working range of 0-60g/cm2.

Date of Award	6 Jan 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Wajira Mirihanage (Supervisor), Anura Fernando (Supervisor) & Nazmul Karim (Supervisor)