Abstract
Printed and flexible sensors are in the focus of recent efforts to establish the advantages of low-cost manufacturing techniques such as screen printing or inkjet printing for printed electronical applications. Devices based on conductive carbon nanotube (CNT) networks within polymeric matrices such as polydimethylsiloxane (PDMS) are already exceeding mere technological demonstrations. Therefore, we investigate the application-oriented behaviour of fully inkjet-printed CNT/PDMS strain sensors under different conditions such as short- and long-term performance. The sensors exhibit a quasi-linear piezoresistive behaviour with vanishing hysteresis to tensile strain. Significant differences in the resistive response between compressive and tensile strain suggest complex re-orientation mechanisms of CNTs inside the matrix. No clear indication for this phenomenon could be observed in the evolution of the CNT network resistance during fatigue measurements within an uncured or cured PDMS matrix, where both scenarios exhibit no visual degradation. However, these measurements over thousands of cycles show different permanent changes in the overall device resistance exhibiting damages but also recovery in the network. Considering these findings facilitates the development of printed sensor devices.
Highlights
P RINTED electronics has become more and more attractive as a complementary method to conventional siliconbased fabrication of electronic devices
A similar trend is reported by Dinh et al [8], where they described a remarkable widening at the starting position of the lines and an agglomeration of multi-walled carbon nanotubes (MWCNTs)
The cured, stabilizing PDMS matrix showed no influence on the electrical conductivity of the CNT network (CNN) but accelerates a permanent rise of R, which is a sign of degradation
Summary
P RINTED electronics has become more and more attractive as a complementary method to conventional siliconbased fabrication of electronic devices. This is due to new possibilities, including the usage of flexible, transparent substrates, high customizabililty and decentralized production. Inkjet printing as an additive deposition technique is already well established in the field of research and development owing to fast prototyping, low production costs, and less demanding production environments compared to cleanroombased lithography processes. Printed electronics allows for applications which require mechanical flexibility, such as strain gauges or biomedical devices. Flexible sensor devices have attracted enormous interest and research efforts within the last years. Utilizing multi-walled carbon nanotubes (MWCNTs) as the sensing
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