Carbon nanotube chemiresistor for wireless pH sensing

Area of Science:

• Biomedical Engineering
• Materials Science
• Sensor Technology

Background:

• Accurate in-vivo pH monitoring is crucial for early detection of surgical implant infections.
• Conventional pH sensors (glass, ISFET) require reference electrodes, risking contamination and leakage.
• Developing a reliable, reference-electrode-free sensor is essential for implantable applications.

Purpose of the Study:

• To develop and characterize a novel solid-state pH sensor for in-vivo monitoring.
• To integrate the sensor with a wireless, passively-powered data transmission system.
• To evaluate the sensor's potential for detecting infection-related acidosis around surgical implants.

Main Methods:

• Fabrication of a solid-state sensor using oxidized single-walled carbon nanotubes (ox-SWNTs) functionalized with poly(1-aminoanthracene) (PAA).
• Testing the sensor's Nernstian response across a wide pH range (2-12) and its stability over 120 days.
• Integration with a passively-powered radio-frequency identification (RFID) tag for wireless data transmission through simulated skin.

Main Results:

• The ox-SWNTs/PAA sensor demonstrated a stable Nernstian pH response from pH 2 to 12.
• The sensor maintained its sensitivity for over 120 days, indicating long-term reliability.
• The wirelessly transmitting, battery-less sensor successfully transmitted pH data through simulated skin.

Conclusions:

• The developed solid-state pH sensor is a promising reference-electrode-free technology for in-vivo monitoring.
• Its wireless, passively-powered nature makes it suitable for implantable biomedical applications.
• This sensor platform has the potential to facilitate early detection of surgical implant infections by monitoring acidosis.