Fiber optic plant wearable sensors for growth and microclimate monitoring

Changes in climate and the growth of population are posing a challenge in plant agricultural industries. Recent technological advances offer new tools for meeting the rising demand for food and energy worldwide. The application of wearable sensors for precision agriculture and their interfacing with plants have more recently emerged as an exciting strategy to monitor plant health. However, the use of plant wearables to improve crop productivity is in its infancy. A few wearable sensors have been designed to monitor growth, microclimate in terms of temperature (T), relative humidity (RH), and light intensity, and plant diseases. Most of these systems are based on electrical sensors that experience a change of resistance, capacitance, or impedance in response to mechanical and chemical inputs. However, some limitations, such as low sensitivity, low signal stability, and high hysteresis error, are still limiting their applications. To overcome these issues, fiber Bragg grating (FBG) technology, with its numerous advantages, can play a crucial role in plant health monitoring. FBG sensors are characterized by good metrological properties, miniaturized size, and biocompatibility, making them suitable for plant wearables development. Moreover, thanks to their easy encapsulation into flexible matrices, FBG can interface with different plant organs (e.g., leaves, stems, fruits). This study proposed soft plant wearable sensors based on FBG technology for plant health monitoring. A soft sensor based on FBG was used for measuring the stem elongation of a tobacco plant. In addition, two other sensors placed on the leaf were used for microclimate monitoring. The promising results open the possibility of using the proposed sensors to promptly diagnose plant health status and optimize the plant growth.