Cellulose Nanopapers

Cellulose nanofibrils (CNFs), also known as nanofibrillar cellulose, are an advanced biomaterial made mainly from renewable forest and agricultural resources that have demonstrated exceptional performance in nanopapers. CNFs possess many unique properties such as nano-scale dimension, high surface area, unique morphology, low density, and superior mechanical strength. Noticeably, CNFs can be easily (chemically) modified and are readily available, renewable, and biodegradable, and thus they are ideal building blocks for nanopapers. In turn, cellulose nanopapers distinguish from traditional papers because of their optical transparency, superior mechanical strength, low density, low coefficient of thermal expansion, and low porosity. This chapter focuses on the progress in the production of CNFs including pretreatment and mechanical isolation, manufacturing of nanopapers, integration of new functionalities such as optical transparency, thermal, electrical, and magnetic properties into cellulose nanopapers, their unprecedented performance, as well as a variety of sustainable, green, and environmentally friendly applications that have been explored so far. Examples of applications for cellulose nanopapers include transparent and flexible transistors and electronics, optical sensing, membranes for water purification, and electret nanogenerators. The general implications for developing future CNF-based nanopapers are also illustrated.