From cotton to functional flexible transparent film for printable and flexible microsupercapacitor with strong bonding interface

Abstract

Turning cotton into functional flexible transparent film is an essential step toward plentiful state-of-the-art applications. Herein, cotton is transformed into functional flexible transparent film by deconstructing macroscopic cotton fibers into nanometer-scale fibers and reconstructing the resulting fibers into a dense structure. The flexible transparent film also demonstrates excellent printability, swellability, degradability, and partially retained hydroxyl groups. Taking advantage of its excellent printability, text and QR-code are printed onto the film with high resolution. Taking advantage of its swellability and retained hydroxyl groups, a flexible rGO/CNT-based microsupercapacitor with strong bonding interface is directly fabricated on the transparent film, while avoiding the addition of insulating binders and exhibiting a thick electrode loading of 16.5 μm. Owing to these unique characteristics, the flexible microsupercapacitor shows an ultrahigh areal capacitance of 39.1 mF cm⁻² at 0.5 mA cm⁻² and a high capacitance retention of 89.5% even under bending angles of 120°. These superior characteristics of the cotton-derived functional flexible transparent film endow it strong advantages over plastic in the wearable device manufacturing and printing field.