A conventional microfabrication process was used to fabricate flexible, film-type pH-sensing electrodes. The pH-sensing electrode was selectively functionalized through electrodeposition within a three-electrode configuration. This setup included a commercial Ag/AgCl reference electrode, a counter electrode made from platinized titanium mesh, and the crafted gold (Au) electrode, which was linked to an electrochemical workstation. The sensing component of the pH sensor was coated with iridium oxide (IrOx) by electrodeposition. The electrodeposition solution comprised 4.5 mM iridium tetrachloride (IrCl4; Thermo Fisher Scientific), 130 mM hydrogen peroxide (H2O2; Merck), and 40 mM oxalic acid dihydrate (C2H2O4·2H2O; Sigma-Aldrich), with the pH adjusted to 10.5 using anhydrous potassium carbonate (K2CO3; Sigma-Aldrich). The mixture was stored in a dark amber bottle at room temperature for 2 days to ensure stability before being refrigerated at ~4°C until further use. The Au working electrode was submerged in this solution, and a pulse potential (0.7 V for 2-s on, followed by 0.0 V for 10-s off) was applied against the commercial Ag/AgCl electrode for a total of 300 pulses. Upon formation of the IrOx pH-sensitive layer, a coating of 2.5% Nafion (Sigma-Aldrich) and pHEMA membranes was applied to improve biocompatibility and extend the operational life of the sensor. The pHEMA precursor solution was prepared with 2-hydroxyethyl methacrylate (Sigma-Aldrich), ethylene glycol dimethacrylate (Sigma-Aldrich), 1-dodecanol (Sigma-Aldrich), and 2,2′-azobis(2-methylpropionitrile) (Sigma-Aldrich). The membrane was subsequently cured thermally at 130°C for 10 min. The finalized film sensor was affixed to a flexible substrate (e.g., PDMS), and an electrical wire was connected by soldering. To protect the connection yet expose the sensor surface to the analyte solutions, the connection point was encapsulated with PDMS.Additional fabrication details and illustrations are provided in fig. S1.