Automated deposition and Joule heating of carbon ink for the generation of on-demand unique thermal patterns

Selective spatial heating is relevant for a number of applications and is enabled by the deposition of heterogeneous materials. Here, we report the automated spray deposition and Joule heating of carbon ink in unique spatial designs to generate on-demand thermal patterns. We demonstrate an automated process using an airbrush-equipped machine to deposit carbon ink onto an electric circuit in a pattern specified to match an arbitrary input. The deposited ink undergoes Joule heating when applied with direct current power, with heating rate inversely proportional to surface resistance. We show that higher areal densities of deposited ink correlate with higher temperatures, which allows for spatial heat patterns, easily achieving temperatures over 100 °C. We find that the resolution (typically on the order of mm) of generated thermal patterns is determined by the applicator geometry and lateral thermal diffusion. The scalability of the automated ink deposition process is demonstrated using a modular applicator design for thermal displays. The resulting thermal patterns also hold promise for use in de-icing systems and site-specific thermoset curing. Graphical Abstract: [Figure not available: see fulltext.]