Durable microfabricated high-speed humidity sensors

Area of Science:

• Materials Science
• Sensor Technology
• Electrochemistry

Background:

• Traditional microfabricated humidity sensors often use gold electrodes, which are prone to oxidative degradation, limiting their long-term stability and performance.
• Existing sensor interrogation methods can compromise response speed or sensor lifespan.

Purpose of the Study:

• To develop a more durable and faster microfabricated humidity sensor.
• To overcome the limitations of gold electrodes in humidity sensing applications.
• To explore the performance of rhodium electrodes in microfabricated humidity sensors.

Main Methods:

• Fabrication of a microfabricated humidity sensor using interdigitated rhodium electrodes on a silicon substrate coated with a Nafion perfluorosulfonate ionomer sensing film.
• Utilized pulsed electroplating techniques for crack-free rhodium deposition.
• Tested sensor response and stability under various excitation conditions, including DC and low-amplitude square waves.

Main Results:

• Rhodium electrode sensors demonstrate significantly improved long-term response stability compared to gold electrode sensors, even with DC excitation.
• Achieved unprecedented response times of 30-50 ms (10-90% rise and fall) at excitation voltages greater than 2 V DC.
• Demonstrated excellent short-term repeatability, with relative standard deviation better than 0.6% (n=7).

Conclusions:

• The developed rhodium-based microfabricated humidity sensor offers superior durability and speed compared to existing technologies.
• The sensor's performance makes it suitable for demanding applications such as breath monitoring and atmospheric measurements.
• Pulsed electroplating is an effective method for depositing high-quality rhodium films for sensor fabrication.