Engineering nanocellulose percolation network for flexible strain sensor

Nanocellulose based flexible strain sensors have emerged as promising wearable electronics to detect various stimuli due to high sensitivity, stretchability, and their eco-friendly nature. Percolation theory, which describes the emergence of long-range connectivity in disordered systems, provides a powerful framework for understanding the relationship between nanocellulose network structures and their strain sensing performances. Studying the behavior of nanocellulose percolation networks helps to elucidate the contribution of the network structure to sensor performances and guides the creation of nanocellulose percolation networks with controlled structures and properties. In this review, percolation theory and its application to nanocellulose percolation networks were briefly introduced. A detailed analysis of the key factors influencing percolation behavior, including nanocellulose morphology, surface modification, aspect ratio, choice of conductive component, and processing techniques was presented. Deformation and strain sensing mechanisms of nanocellulose percolation networks, and factors that affect their strain sensing performances were then discussed. Special attention was paid to the strategies and advancements in modulating nanocellulose percolation networks to enhance their performance in sensitivity and stretchability. Ultimately, this work offered a perspective on the future of flexible strain sensors based on nanocellulose percolation networks, highlighting both its promising outlook and remaining challenges.