Miniature pH sensors on ultra-flexible substrates

We have developed a pH sensor consisting of iridium oxide (IrOx) and silver chloride (AgCl) electrodes based on ultra-flexible substrates with robust performance and simple fabrication processes. The sensor was fabricated by sol-gel coated IrOx film and patterned by laser cutting. AgCl reference electrode was deposited by printing. The pH sensor was tested in flat and deformed conditions. A mechanical apparatus was made to test the sensors in deformed situations. In both scenarios, it showed a promising sensitivity of 49.3 mV/pH in the pH range between 2 and 13 at the room temperature. The response time, stability, reversibility, and repeatability of the sensors were investigated in both types of physical settings. The ultra-flexible pH sensor shows unique capability to be conformed to curved surfaces while provides excellent performance.