Wood Ionic Cable

Abstract The combination of good stability, biocompatibility, and high mechanical strength is attractive for bio‐related material applications, but it remains challenging to simultaneously achieve these properties in a single, ionically conductive material. Here a “wood” ionic cable, made of aligned wood nanofibrils, demonstrating a combination of biocompatibility, high mechanical strength, high ionic conductivity, and excellent stability is reported. The wood ionic cable possesses excellent flexibility and exhibits high tensile strength up to 260 MPa (in the dry state) and ≈80 MPa (in the wet state). The nanochannels within the highly aligned cellulose nanofibrils and the presence of negative charges on the surfaces of these nanochannels, originating from the cellulose hydroxyl groups, provide new opportunities for ion regulation at low salt concentrations. Ion regulation in turn enables the wood ionic cable to have unique nanofluidic ionic behaviors. The Na + ion conductivity of the wood ionic cable can reach up to ≈1.5 × 10 −4 S cm −1 at low Na + ion concentration (1.0 × 10 −5 mol L −1 ), which is an order of magnitude higher than that of bulk NaCl solution at the same concentration. The scalable, biocompatible wood ionic cable enables novel ionic device designs for potential ion‐regulation applications.