Reviewed by Lexie CornerJan 22 2025
Researchers from Auburn University in Alabama have developed precise and reliable paper-based temperature and humidity sensors. The environmentally friendly sensors were described in the Journal of Laser Applications, published by AIP Publishing.
Dry additive nanomanufacturing for printing humidity and temperature sensors. Image Credit: Masoud Mahjouri-Samani
Greenhouses and open farms, which facilitate the production and sale of locally grown produce and meat, are becoming increasingly integral to modern food systems. Producers require precise methods to monitor environmental conditions, optimizing greenhouse crop growth and yields while maintaining the quality and freshness of harvested produce during storage. Advanced sensor technology capable of monitoring and controlling temperature and humidity is critical for addressing the global demand for sustainable food production.
The necessity of accurately measuring temperature and humidity across diverse agricultural conditions has spurred the development of various sensor systems. However, ensuring these systems are both operationally effective and environmentally sustainable while remaining cost-efficient continues to present significant challenges.
In recent years, agriculture has been hit heavily by drastic changes in environmental factors such as humidity and temperature, thereby driving the urgency for innovative solutions to enhance productivity and improve quality with minimal environmental impact.
Masoud Mahjouri-Samani, Associate Professor, Auburn University
Flexible electronics and sensors can be manufactured using techniques such as aerosol-jet printing, inkjet printing, gravure printing, and screen printing. However, these processes, which rely on liquid-based materials, are typically incompatible with biodegradable substrates, leading to the predominant use of non-biodegradable plastics.
Paper presents a viable alternative to conventional plastic substrates. Its cellulose fibers provide a porous surface, and it is biodegradable, widely available, and environmentally sustainable.
Researchers fabricated temperature and humidity sensors by printing silver lines on four types of commercially available paper using dry additive nanomanufacturing.
The sensors detect environmental changes by measuring variations in electrical properties. For humidity sensing, the paper's ability to absorb water vapor alters the capacitance of the printed electrodes, reflecting changes in relative humidity. For temperature sensing, changes in resistance occur as the metallic conductor’s resistivity increases with rising temperature.
The sensors demonstrated reliability and sensitivity, effectively detecting relative humidity levels between 20 % and 90 % and temperature variations from 25 °C to 50 °C. These biodegradable sensors are also cost-effective, reusable, and can be safely disposed of at the end of their life cycle.
Mahjouri-Samani concluded, “By integrating advanced techniques like dry additive nanomanufacturing with biodegradable substrates, this research combines functionality with environmental responsibility, addressing the growing concern of the disposal of electronic equipment. This approach offers the potential to revolutionize smart agricultural practices by enabling precise monitoring of key factors in plant growth.”
Journal Reference:
Jaiswal, S., et. al. (2024) Laser-assisted dry printing eco-friendly paper-based humidity and temperature sensors. Journal of Laser Applications. doi.org/10.2351/7.0001652