SitS NSF-UKRI: Phytoelectronic Soil Sensing

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

The research objectives of this project at the University of Colorado, University of Cambridge in the UK and USDA-ARS are to measure the state of the soil accurately, densely and remotely using plants as in situ chemical laboratories. Correlations between the state of the soil and the contents of the major water-conducting tissue in plants, the xylem, are well-established. Xylem contents will be analyzed in "interrogator plants" by implanting bioelectronic sensors in plant stems, inducing xylem to form around them and remotely communicating data from these sensors by low-power radio transmission. This approach will avoid the complexity of sensing the soil directly by instead detecting the chemical response of vascular fluids to chemical and biological changes in the soil around the roots. These fluids, which are transported by the woody xylem tissues, are under negative pressure and thus typically difficult to access. The project will therefore investigate a number of regeneration techniques for surgically implanted, small sensors such that these sensors become associated with xylem tissue in graft junctions, much like the grafting currently used routinely in fruit trees. The entire small sensor including implanted electronics and regenerative coating will be screen-printed for very low cost. Screen printing recipes and other enabling techniques will be shared with the public through the Open Science Framework. Public use of these results will be further fostered by funded kits distributed to teams through the international BioMaker and OpenPlant programs. The research will explore the new field of phytoelectronics, the convergence of botany for biorecognition, bioelectronics for chemo-sensing, internet-of-things (IoT) electronics for communication, and machine-learning for classification. The goals of the research are to 1) create an inexpensive, potentially biodegradable platform for multi-variate sensing of the soil utilizing the inherent robustness of living plants to operate autonomously in variable conditions; 2) merge these plants with the IoT in which buried roots extract and communicate soil state chemically to embedded multi-analyte, electronic sensors that then digitize and relay these data to servers for integration and machine learning; and 3) advance understanding of the interaction of soil and the biosphere by selecting plants specialized for specific chemical, pathogen or ecological signals and using them as instruments. The team will accomplish these goals by 1) printing the multi-analyte sensors based on arrays of organic electrochemical transistors individually functionalized with ion specific membranes, 2) creating printable drug-release coatings for the electronics that encourage regeneration of xylem tissue near the surgically implanted sensor, and 3) connecting these "chipped plants" to RFID or LoRA backscatter communication tags which are interrogated remotely to retrieve digitized sensor response. At program end, the combination of these studies should enable the soil nitrate concentration in a cornfield to be monitored daily with resolution down to square meters. This project was awarded through the "Signals in the Soil (SitS)opportunity, a collaborative solicitation that involves the ENG/CBET and BIO/IOS divisions of the National Science Foundation (NSF), the United States Department of Agriculture National Institute of Food and Agriculture (USDA NIFA) and the following United Kingdom Research and Innovation (UKRI) research councils: 1) The Natural Environment Research Council (NERC), 2) the Biotechnology and Biological Sciences Research Council (BBSRC), 3) the Engineering and Physical Sciences Research Council (EPSRC), and the Science and Technology Facilities Council (STFC). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.