Determination and validation of heat generation from printed heaters using inkjet-printed thermochromic optical sensor layers

In this work, we present an approach to stimulate and control the heating effect across a glass substrate using inkjet-printed heaters, while simultaneously monitoring the surface thermal behavior through printed thermochromic layers with optical sensing capabilities. The thermochromic coating provides a direct optical indication of sudden temperature increase, as it exhibits an irreversible color change upon surpassing a defined threshold temperature. This method allows the straightforward identification of critical thermal events and localized instabilities without the need for complex measurement systems. For localized heating, silver meander structures with a line width of about 500 µm were manufactured on glass, resulting to an electrical resistance ranging between 170 -260 Ω. Prototype devices were developed by inkjet printing the heating elements on one side of the substrate and the thermochromic layer on the other side. Electrical characterization demonstrates that the partial or localized color change occurred at sub-threshold power inputs, while a complete and uniform color transitions was achieved at a higher input power levels ranging between 44 -46 W, leading to a peak surface temperature of 270 °C and above, enabling full activation of the thermochromic layer. This approach may be extended to conventional electronic components by integrating a suitable printed thermochromic layer directly onto their surfaces, offering a simple and low-cost method for thermal monitoring, overheat protection and failure prevention. The combination of functional printing with thermochromic detection thus holds promise for applications in quality assurance, safety monitoring, and the development of robust next generation electronics systems.