High-performance strain sensors based on fragmented carbon nanotube structures

Stretchable strain sensors are needed for emerging applications like wearable electronics, artificial e-skins, bionic sensory systems as well as deployable structures. The crucial factors that govern the performance of such sensors are sensitivity, stretchability, and linearity. High gauge factor sensors are vital for small strain detection and open up opportunities for exploration of subtle strain detection. The stretchability determines the sensing strain range. Finally, despite it is needed for robust measurements and easy post processing, linearity of the response is challenging for stretchable strain sensors as severe changes in configuration might take place between the reference and the deformed configuration. Most of the developed sensors feature poor performance for at least one of these three criteria. We propose here to rely on cracked structures to solve all issues together. Cracks are considered detrimental to the overall mechanical and electrical properties of materials. However, if these cracks can be controlled, they also have the potential for use in mechanical sensing applications. In this study, we demonstrate that strain sensors based on fragmented single-walled carbon nanotube (SWCNT) assemblies embedded in poly (dimethyl siloxane) (PDMS) can maintain their sensitivity at very high strain levels. Our strategy here is to develop a new family of sensors taking advantage of the special properties of fragmented carbon-nanoparticles based structures (papers and wires). We systematically describe how to control the fragmentation of the conductive CNT papers or wires for achieving high-performance strain sensors. This fragmentation based sensing system brings opportunities to engineer highly sensitive stretchable sensors.