Stanford University

Stanford University will develop a non-contact root imaging system that uses a hybrid of microwave excitation and ultrasound detection. Microwave excitation from the surface can penetrate the soil to the roots, and results in minor heating of the roots and soil at varying levels depending on their physical properties. This heating creates a thermoacoustic signal in the ultrasound domain that travels back out of the soil. The team’s advanced ultrasound detector has the ability to detect these signals and maintain sufficient signal-to-noise ratio for imaging and root biomass analysis. The team will develop a suite of image processing algorithms to convert the data into an understanding of root properties including structure, biomass density, and depth. Plant physiologists from the Carnegie Institution for Science will partner with Stanford to characterize maize roots under various drought conditions as well as soil type and density variations. Since the entire system is non-contact, it eliminates the need to make good physical contact with the irregular soil surfaces. Over a three-year period, the team will first demonstrate the feasibility of non-contact thermoacoustics for root imaging under laboratory conditions, then develop and test a thermoacoustic system in the field. If successful, Stanford’s system could examine root structures in a noninvasive manner that produces images far more advanced than current imaging methods.