Direct printing of conductive hydrogels using two-photon polymerization

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) based conductive hydrogels have been extensively used for bioelectronics and tissue engineering applications owing to their high electrical conductivity and ability to interface with soft biological tissues. However, the fabrication of PEDOT:PSS-based hydrogels has mostly relied on conventional fabrication techniques such as casting and transfer printing, which limits the feature size to micro- or mesoscale. To address these limitations, this study offers a novel PEDOT:PSS-based hydrogel material that can be printed directly to nano/microscale structures using the Two-Photon Polymerization (TPP) technique. The TPP-printability of the newly developed hydrogel was analyzed, and its printing window was characterized. The prepared hydrogel exhibits enhanced radial swelling, electrical properties, and biocompatibility compared to the pristine PEDOT:PSS. To validate the micro-manufacturing feasibility of hydrogel, several microstructures were fabricated using the TPP process. The fabricated microstructures demonstrate many properties, including electrical conductivity, biocompatibility, high resolution, and structural stability. The direct printing of highly conductive PEDOT:PSS hydrogel micro-devices overcomes the limitations of traditional conductive hydrogel manufacturing methods. It opens up new possibilities for applications in micro-energy storage devices, flexible micro/nanoelectromechanical systems (MEMS), and flexible biomedical micro-devices. The combination of high-resolution direct printing and unique hydrogel properties offers promising opportunities in these fields.