Highly conductive and stretchable conductors fabricated from bacterial cellulose

Advanced materials that can remain electrically conductive under substantial elastic stretch and bending have attracted extensive interest recently owing to their broad application potentials, particularly for flexible electronics. Here, we have developed a simple and inexpensive method to fabricate highly conductive and stretchable composites using bacterial cellulose (BC) pellicles as starting materials, which can be produced in large amounts on an industrial scale via a microbial fermentation process. The prepared pyrolyzed BC (p-BC)/polydimethylsiloxane (PDMS) composites exhibit a high electrical conductivity of 0.20–0.41 S cm−1, which is much higher than conventional carbon nanotubes and graphene-based composites. More importantly, the p-BC/PDMS composites that combine high stretchability with high conductivity show great electromechanical stability. Even after 1000 stretching cycles at the maximum strain of 80%, the resistance of the composites increased by only ∼10%. The resistance increased slightly (∼4%) after 5000 bending cycles with a maximum bending radius of 1.0 mm. Shu-Hong Yu and co-workers at the University of Science and Technology of China in Hefei have devised an easy and cost-effective approach to prepare flexible conductors. Increasingly, conducting materials are required to be stretchable and bendable - properties that are difficult to achieve with conventional conductors. Yu and colleagues have now turned to bacterial cellulose to get around this problem. Although cellulose is mostly known as a component of plants, it can be generated, in high purity, by some micro-organisms through fermentation - a facile process that can be carried out in large quantities. Bacterial cellulose pellicles were treated by freeze-drying and pyrolysis to give a robust aerogel composed of entangled nanofibres, which was then infiltrated with a polymer. The resulting composite material showed excellent electrical conductivity, which was maintained even under stretching and bending, and is thus very well suited to applications in flexible, foldable electronics. Highly conductive and stretchable conductors from bacterial cellulose (BC) can be fabricated through a simple and inexpensive method using bacterial cellulose pellicles as starting materials, which can be produced in large amounts on an industrial scale via a microbial fermentation process. The prepared pyrolyzed BC/polydimethylsiloxane composites exhibit highly stable electric conductivity even under high stretching and bending strain.