Non-Contacting Plant Health Monitoring via Ultrasound in Ambient Air

In this work, we report a non-destructive and non-contacting ultrasound system with a novel air-coupled transducer to continuously monitor the drying process of prickly pear (nopal) pads in a lab environment. Compared with conventional imaging and spectroscopic methods or electrical-based approaches, ultrasound-based methods are non-invasive, cost-effective, and suitable for large volume evaluation. The time-dependent elastic modulus of the cactus can be obtained and monitored by using our proposed ultrasonic method. The evaluated elastic modulus behavior shows a good agreement with the destructive testing results in the existing literature. With further development, the proposed method can be used for in vivo plant health monitoring.