Fully Inkjet-Printed Carbon Nanotube-PDMS-Based Strain Sensor: Temperature Response, Compressive and Tensile Bending Properties, and Fatigue Investigations

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.