A wearable flower-shaped sensor based on fiber Bragg grating technology for in-vivo plant growth monitoring

One of the biggest challenges facing the world agriculture is feeding a growing population in a sustainable way. Therefore, global food availability is under a severe strain exacerbated by climate changes and biological stresses. Moreover, the content of macro- and micronutrients obtained from in plant-food sources strongly depends on the plant development. An attractive strategy to increase agricultural productivity is the growth monitoring of plants and edible parts by using wearable systems. However, most of these tools measure dimensional changes uniaxially, while an accurate representation of the growth distribution requires multipoint strain measurement especially for plants that show an anisotropic development. Here, we present a stretchable multisensor wearable system highly adaptable to the curvilinear surface of leaves and fruits for multidirectional dimensional monitoring. The proposed sensor consists of six fiber Bragg gratings (FBGs) within a biomimetic flexible substrate with a flower design. FBGs with their miniaturized size, high metrological properties, and multiplexing capacities are well suited to this purpose. A finite-element model (FEM) guides the optimal design and sensors positioning within the flower-shaped matrix to exhibit an adequate strain sensitivity and negligible crosstalk effects among the six sensing elements with a reduced encumbrance. A metrological characterization is first performed followed by the application of the proposed system for in-vivo detection of dimensional changes of a leaf and fruit in both indoor and outdoor scenarios.