Transfer Printing with Cellulose Nanofibers for Fabrication of 3D Electronics

As an emerging technology, three-dimensional (3D) conformable electronic devices on complex surfaces have received increasing attention in recent years. However, their potential is constrained by the lack of effective fabrication techniques, as traditional printing methods face challenges such as the demanding process for mapping and harsh conditions. To address this, we present a mild-conditioned transfer printing technique using carboxymethylated cellulose nanofibers (CM-CNF) enabled by a water-assisted adhesion switching method. CM-CNF films were produced via a combination of chemical carboxymethylation and mechanical grinding. By optimizing the surface charge and hydrophilicity of CM-CNF, the efficiency of transfer printing was enhanced. The high smoothness of CM-CNF films, achieved through sufficient mechanical grinding, facilitated high-resolution ink deposition and easy delamination. To demonstrate the application of this technique in 3D electronics, we fabricated precise electronic devices with polyvinyl butyral (PVB) and silver nanowire (AgNW) using direct ink writing (DIW) on CM-CNF films and transferred the pre-fabricated devices on 3D surface. Modifying the interfacial bonding strength between CM-CNF and PVB-based ink through hydration of the CM-CNF film enabled efficient transfer printing. This water-assisted adhesion switching method requires only hydration, avoiding damage to the ink or target substrate. This technique shows great potential for fabricating 3D electronics on various target substrates and wearable devices.