Humidity Sensors Based on Cellulose Nanofiber Fabricated on a Three-Dimensional (3D) Curved Surface

Area of Science:

• Materials Science
• Electronics Engineering
• Sensor Technology

Background:

• Traditional printed electronics face challenges with dielectric performance and resolution on 3D structures.
• Integrating components directly into 3D-printed materials during manufacturing is an ongoing area of research.
• Direct printing on 3D curved surfaces requires specialized techniques to overcome resolution limitations.

Purpose of the Study:

• To develop and demonstrate a humidity sensor fabricated on a 3D curved surface.
• To utilize 3D-printed interdigital electrodes (IDE) and cellulose nanofibers for humidity sensing.
• To evaluate the sensor's performance, including repeatability and sensitivity, on non-flat substrates.

Main Methods:

• Fabrication of an interdigital electrode (IDE) sensor using a double blanket reverse offset printing technique on both flat and 3D-curved glass substrates.
• Coating a cellulose nanofiber emulsion as the sensing layer onto the IDE pattern using a dispenser.
• Measuring the electrical impedance of the fabricated sensor across a relative humidity (RH) range of 10% to 90%.

Main Results:

• The 3D-printed humidity sensor exhibited high repeatability and sensitivity.
• Successful fabrication and performance of the sensor were demonstrated on a 3D curved glass substrate.
• The sensor's electrical impedance correlated with changes in relative humidity.

Conclusions:

• The developed humidity sensor technology is promising for integration with 3D deformable surfaces.
• This approach overcomes limitations of traditional printed electronics on complex geometries.
• The cellulose nanofiber-based sensor offers a viable solution for humidity monitoring in unconventional electronic applications.