Synthesized biocompatible and conductive ink for 3D printing of flexible electronics

Three-dimensional (3D) printing is an efficient technique for the fabrication of electronic devices. It also enables the use conductive of biomaterials in various applications, such as implants and flexible devices. Designing a new bioink is extremely challenging. For bioelectronics devices, bioink materials should be printable, flexible, conductive, harmless to cells, and sufficiently strong to maintain their shape when immersed in nutrients or under pressure. Over the past few years, several flexible conductive bioinks have been developed that are based on composite pastes containing a biopolymer and conductive micro- and nanoscale materials in the form of metallic particles, conducting polymers, or a mixture of them. Herein, we report a new strategy for the fabrication of a bioink for a commercial 3D printer with the desired conductivity, mechanical properties, and biocompatibility, using a poly(glycerol-co-sebacate) (PGS)-based polymer and zinc. The PGS-based polymer and lithium phenyl-2,4,6-trimethylbenzoylphosphinate (as a photoinitiator) were added to the zinc, and then, the prepared bioink was polymerized during 3D printing under visible light. According to a microstructural investigation using scanning electron microscopy, the zinc particles were homogeneously distributed in the PGSA matrix. The conductivity of bioink increases with chemical sintering and with an increase in the amount of zinc particles. Based on rheology tests, the appropriate printable composition is 60% zinc and 40% PGS-based polymer. This bioink exhibited remarkable mechanical and adhesive properties in comparison with the PGS-based polymer without zinc, according to tensile, compression, lap shear, wound closure, and burst pressure modules. In vitro and in vivo results indicated that the bioink was not toxic to the cells or the animal over a period of culturing.