Development of Inkjet Printing Biosensor on Flexible and Porous Substrates
In this work, we report the direct fabrication of inkjet-printed sensors on flexible, porous, and paper substrates. Inkjet printing technology is a promising technique that is capable of testing new materials and fast prototype fabrication. Nowadays, we can find inks with low sintering temperatures allowing this technology to work with fragile substrates. Here we present novel fabrication technique of electrochemical sensors on three different substrates plastic (PEN), Microporous polytetrafluoroethylene (PTFE), and paper (Whatman No.1) were all active elements were printed directly on the substrate. Sensors have been fully characterized for pH, dissolved oxygen (DO), and detection of cortisol. The pH sensor was developed on PEN substrate using two different indicator electrodes, one made of rough Pt and the other with aromatic Au. The Pt electrode shows enhanced performance stability of electrodeposited iridium oxide. Additionally, it shows long-term stability, highly sensitive, and excellent reproducibility with a linear response (71.3 mV/pH unit) in a wide pH range (pH 2-11). On the other hand, we printed a PANI:PPy ion-selective membrane on aromatic Au, obtaining a full inkjet printed pH sensor. Moreover, the PANI:PPy sensor shows a high sensitivity with a linear response (81.5 mV/pH unit) in a pH range from 3 to 10. The DO sensor was fabricated on the PTFE membrane for an organ-on-a-chip system. The sensor measures the oxygen consumption of human and rat cells in real-time by amperometry technique. And finally, for cortisol detection, a three array electrode was fabricated on paper with a novel technique that allows us to tune the electrochemically active area. The developed sensor demonstrated sensitivity toward cortisol in the concentration range of 5 to 20 ng/ml. These novel approaches are useful to simplify the fabrication process on a wide range of substrates.