Review article: Plant-inspired robotics: a comprehensive review based on on-/off-plant behaviours and future perspectives

Abstract. Plants have evolved diverse strategies to survive and thrive in competitive natural environments. Their behaviours and mechanisms provide a rich source of inspiration for the design of innovative robots and have attracted growing attention from the robotics community over the past decades. Corresponding to the typical plant life cycle, this review introduces a new framework that categorizes plant-inspired robots into two main groups, i.e. robots inspired by on-plant and off-plant behaviours. Theoretically, all plant-inspired robots can be covered in this categorization framework. On-plant behaviours refer to movements exhibited by plants as monolithic living systems, and four categories of robots inspired by corresponding on-plant behaviours, including growth, gripping, trapping, and other specialized behaviours, are discussed. Off-plant behaviours involve movements of both parent plants and detached parts for seed dispersal. Robots inspired by three types of off-plant behaviours (wind dispersal, ballistic dispersal, and humidity-driven self-locomotion of seeds) are reviewed in detail. Furthermore, two conceptual research directions are proposed for the long-term development of the plant-inspired robots: (1) natural plant optimization re-inspired by robotics based on synthetic biology and (2) the development of exoplanet robots inspired by plant survival strategies. Due to their unique advantages, such as structural compliance, low cost, eco-friendliness, environmental adaptability, and responsiveness to stimuli, plant-inspired robots show application values in agriculture, biomedicine, environmental monitoring, and beyond. More advanced plant-inspired robots are expected to emerge in the upcoming future along with expanding knowledge of plant biology and growing research interest, which enables this review to be continuously refined and expanded.