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Paper-based sensors provide eco-friendly, affordable way to monitor global agriculture

Greenhouses and open farms that welcome visitors to purchase locally grown produce and meat have become increasingly important to food productivity. Not only are farmers looking for ways to monitor conditions to help improve greenhouse crop growth and yield, but keeping harvested food fresh in storage conditions is also a major concern.

Smart sensor technology, monitoring and controlling temperature and humidity, plays an essential role in producing enough food to meet the ever-increasing demand for the worldwide population.

In the Journal of Laser Applications, researchers at Auburn University in Alabama present paper-based temperature and humidity sensors that are accurate and reliable, as well as eco-friendly.

Measuring temperature and humidity in a variety of crop-growing circumstances has prompted the development of numerous sensors, but ensuring these devices are effective while remaining environmentally friendly and cost-effective is a challenge.

"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," said author Masoud Mahjouri-Samani.

Flexible electronics and sensors are quickly and easily manufactured. The print technologies used in producing these sensors include methods such as aerosol-jet printing, inkjet printing, gravure printing, and screen printing. Due to the liquid nature of these techniques and their incompatibility with biodegradable base materials, most printing is done on nonbiodegradable plastics.

Paper is an excellent alternative to these traditional plastic materials. Its cellulose fibers provide a porous surface, and it is biodegradable and abundant.

The research team created temperature and humidity sensors by printing silver lines on four types of commercially available paper through a process called dry additive nanomanufacturing.

Changes in the ability to store electrical energy, called capacitance, and resistivity in the printed electrodes are monitored to determine shifts in temperature and humidity. As the paper absorbs water vapor, its capacitance change is measured to reflect the relative humidity of the environment.

The temperature-sensing mechanism relies on changes in resistance. As the temperature increases, the metallic conductor experiences an increase in resistivity.

The sensors proved reliable and sensitive to changes in temperature and humidity levels. They successfully detected changes in relative humidity levels from 20% to 90% and temperature variations from 25°C to 50°C. Additionally, the biodegradable sensors are affordable and can be reused, and when the time comes, they can be disposed of safely.

"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," said Mahjouri-Samani.

"This approach offers the potential to revolutionize smart agricultural practices by enabling precise monitoring of key factors in plant growth."