In Situ UV-Assisted Direct Ink Writing of High-Resolution Silver Inks for Fine-Line Sensor Applications

Direct ink writing (DIW) is a promising additive manufacturing technique for flexible electronics; however, lateral spreading of conventional silver inks often limits printing resolution and geometric fidelity. To address this limitation, an in situ UV-assisted DIW strategy using photocurable silver inks was developed for the fabrication of high-resolution conductive features. The effects of Ag loading, TPO photoinitiator concentration, and dispersant type on the rheological behavior, photocuring response, and stability of the inks were systematically investigated. Excessive TPO concentrations were found to induce rheological instability, whereas an optimized formulation enabled a stable photocuring response. Among the dispersants investigated, AH100 provided the most favorable balance between ink flowability and controlled substrate wetting, thereby suppressing excessive lateral spreading. During printing, in situ UV irradiation rapidly promoted crosslinking of the resin matrix, increasing the structural rigidity of the deposited filament and restricting capillary-driven spreading. Using the optimized printing conditions and a photocurable silver ink with a Ag powder-to-photosensitive resin mass ratio of 4:1, the post-sintering line width was reduced from 269.8 to 72.57 μm, corresponding to a reduction of approximately 73%. After sintering at 800 °C, the printed tracks exhibited an electrical conductivity on the order of 107 S/m, demonstrating that the substantial improvement in printing resolution was achieved without significantly compromising electrical performance. This in situ UV-assisted DIW strategy therefore provides an effective route for fabricating fine conductive features with improved dimensional fidelity and competitive electrical performance, showing promise for high-resolution flexible electronics and sensor applications.