Exploring the Mechanisms of Humidity Responsiveness in Plants and Their Potential Applications

Plant structures exhibit complex behaviors through unique shape changes and movements closely related to moisture factors. When the plants absorb moisture, their inside has a higher tension than their outside, so the entire structure is folded to closure or opened. The principle and property could be applied to bio-inspired technology, which is the process of fusion mimicking the structure, function, metabolism, mechanism, and ecological system of those creatures adapted to their environments. In this study, we analyzed the functions and physical characteristics of environment-sensing plants to demonstrate the principles of plants with opening-and-closing and curling-and-uncurling mechanisms and to better understand these behavior principles. From a biological and ecological viewpoint, the target sensory and cognitive plants that respond to external humidity and vibration were found to undergo structural changes in the size of the xylem and the degree of adhesion of the leaf and stem, as well as the opening, closing, and curling of the external shapes of the plants. The phenomenon of external form changes based on the microstructural characteristics of plants showed a promising direction for addressing issues in existing technology, such as non-powered operation. Therefore, in this study, we presented a biomimetic humidification model that was biocompatible and reversible. Pinecone samples with the applied opening-and-closing mechanism were to apply these biological properties to biomimetics. The results provide biomimetic knowledge for understanding the functions of biological and ecological features underlying the morphological changes in humidity-sensing plants and plant bioacoustics. These bio-inspired plant resources could provide sustainable new-growth power and valuable scientific information for advancing the research and technological development of biomimetics.