Wireless IrO ₂ Electrochemical Sensor System for Real-Time pH Monitoring in Microliter Volumes

Area of Science:

• Electrochemistry
• Materials Science
• Nanotechnology

Background:

• Accurate pH measurement in microliter volumes is crucial for point-of-care diagnostics and real-time analysis.
• Existing methods often lack the sensitivity, stability, or portability required for decentralized applications.

Purpose of the Study:

• To develop a wireless electrochemical pH sensor system for continuous, real-time monitoring of pH in small sample volumes.
• To integrate nanostructured iridium oxide (IrO2) with electron-beam-evaporated, photolithographically patterned gold electrodes (EBLG) and a low-power Bluetooth potentiostat.

Main Methods:

• Fabrication of IrO2 nanostructures on EBLG electrodes.
• Characterization using FESEM, Raman, and XPS.
• Integration with a wireless potentiostat for data streaming to a smartphone.

Main Results:

• The IrO2/EBLG sensor demonstrated near-Nernstian sensitivity (69.7 mV/pH) from pH 2-9.
• Fast response time (~10 s), negligible hysteresis, and low potential drift (<0.28 mV/h).
• High selectivity, reproducibility, and long-term stability, with measurements agreeing with commercial devices (p > 0.05).

Conclusions:

• The developed IrO2/EBLG platform offers a stable, miniaturized, and wireless solution for decentralized pH sensing.
• This technology is suitable for real-time monitoring in biological, food, and environmental samples.
• It presents a promising approach for wearable and field-deployable pH monitoring systems.