Have you ever wondered if your plants are too dry or not getting enough water? Farmers and plant lovers might soon have a way to check this quickly, in real time.
Scientists have been working on special sensors that can detect different chemicals in the past ten years. One challenge has been creating sensors that can work inside living plants.
But now, researchers from the Singapore-MIT Alliance for Research and Technology (SMART) have developed new sensors that can detect pH changes in plants. This change in pH can show when a plant is stressed due to lack of water (drought stress). These sensors can help farmers and gardeners catch drought stress early before it causes serious damage to the plants.
Researchers have created the world’s first sensors made from covalent organic frameworks (COFs) combined with silk fibroin (SF) microneedles. The sensors can detect a decrease in acidity in the plant’s xylem tissues, an early sign of drought stress. This technology can warn farmers and gardeners about drought stress up to 48 hours before traditional methods detect it.
Covalent organic frameworks (COFs) designed as chromatic sensors are opening new ways to study biological systems. When combined with materials that are safe for living organisms, these sensors can explore how chemicals interact within plants and other living systems. One exciting possibility is using these sensors for “chemical tomography,” creating 3D maps of chemical details inside living organisms.
SMART’s breakthrough addresses a long-standing challenge for COF-based sensors, which were unable to interact with biological tissues until now.
Professor Michael Strano, co-corresponding author, DiSTAP co-lead principal investigator, and the Carbon P. Dubbs Professor of Chemical Engineering at MIT, said, “This type of sensor can be easily attached to the plant and queried with simple instrumentation. It can, therefore, bring powerful analyses, like the tools we are developing within DISTAP, into the hands of farmers and researchers alike.”
Professor Benedetto Marelli, co-corresponding author, principal investigator at DiSTAP, and associate professor of civil and environmental engineering at MIT, said, “The COF-silk sensors provide an example of new tools that are required to make agriculture more precise in a world that strives to increase global food security under the challenges imposed by climate change, limited resources, and the need to reduce the carbon footprint. The seamless integration between nanosensors and biomaterials enables the effortless measurement of plant fluids’ key parameters, such as pH, allowing us to monitor plant health.”
This new method allows scientists to create 3D maps of pH levels inside plant tissues using a smartphone camera while the plant is still alive. This approach is much less invasive and faster than traditional methods, which can be slow and damage the plant.
Researchers at DiSTAP have designed and created four COF compounds that change color in response to changes in pH levels, known as tunable acid chromism. They applied these COF compounds onto silk fibroin (SF) microneedles, which are clear and flexible. The combination of SF microneedles and the COF film makes it possible to observe and visualize how pH levels change across different plant areas. As the pH changes, the color of the COF film shifts, allowing scientists to see the spatial distribution of pH levels inside the plant in real time.
Song Wang, research scientist at SMART DiSTAP and co-first author, said, “Building on our previous work with biodegradable COF-SF films capable of sensing food spoilage, we’ve developed a method to detect pH changes in plant tissues. When used in plants, the COF compounds will transition from dark red to red as the pH increases in the xylem tissues, indicating that the plants are experiencing drought stress and require early intervention to prevent yield loss.”
Yangyang Han, senior postdoc at SMART DiSTAP and co-first author, said, “SF microneedles are robust and can be designed to remain stable even when interfacing with biological tissues. They are also transparent, allowing multidimensional mapping to be minimally invasive. Paired with the COF films, farmers now have a precision tool to monitor plant health in real time and better address challenges like drought and improve crop resilience.”
Journal Reference:
- Wang, S., Han, Y., Reddy, V.A. et al. Chromatic covalent organic frameworks enabling in-vivo chemical tomography. Nat Commun 15, 9300 (2024). DOI: 10.1038/s41467-024-53532-7
