Bacterial Bioprinting on a Flexible Substrate for Fabrication of a Colorimetric Temperature Indicator by Using a Commercial Inkjet Printer

Bacterial sensors are recommended for medical sciences, pharmaceutical industries, food industries, and environmental monitoring due to low cost, high sensitivity, and appropriate response time. There are some advantages for using bacterial spores instead of bacteria in vegetative forms as spores remain alive without any nutrient for a long time and change to vegetative form when a suitable environment is provided for them. For biosensor fabrication, it is important to defne how the bacterial spores are delivered on the substrate media. In this study, a commercial inkjet printer (HP Deskjet 1510) was employed for transferring bacterial spores on a flexible substrate media, while in the previous studies, mostly, special printers were evaluated for transferring bacteria on rigid flms. Here, printed bacterial spores were used as calorimetric indicators for temperature. The custom‑made bio‑ink was made of bacterial spores along with gelling agent and pH indicator. The change in the temperature would have transformed bacterial spores into vegetative bacteria. This transformation would change bio‑ink pH to an acidic level that can be detected by a color change.