Patterning Electronically Conductive Features Within Soft Hydrogel Substrates for Bioelectronics and Tissue Engineering Applications

Hydrogels, highly hydrophilic polymeric networks, have gathered significant attention in the biomedical field due to their exceptional water-retention capability, biocompatibility, and anti-biofouling properties. The mechanical properties of hydrogels can be tuned with their composition, and type and degree of crosslinking. Moreover, hydrogels exhibit excellent ionic conductivity due to their ability to swell to many times their dried volume in aqueous solutions. The synergy of these two features makes hydrogels ideal for mimicking natural soft tissues. However, their lack of electronic conductivity limits their applicability in bioelectronics. Moreover, many applications in bioelectronics would strongly benefit not only from the electrical conductivity in the hydrogel, but from the ability to pattern it, a feature that has not been demonstrated at the sub-µm length scale thus far.<br/>In this presentation, I will introduce a method to fulfill these requirements. Exploiting two-photon direct laser writing (DLW), we trigger the in-situ synthesis of noble metal nanoparticles (NPs) through photoreduction. Thereby, we generate electrically conductive 50-250 µm wide tracks within both synthetic and natural hydrogels possessing Young’s moduli as low as 20 kPa, matching the mechanical properties of soft natural tissues.<br/>We envision this method could be used for the fabrication of hydrogel-based devices and functional substrates for tissue engineering. Lastly, the introduction of spatially-controllable electronic conductivity within hydrogels would open new possibilities for interfacing soft materials with electronic equipment.