Plant robotics shows how living movement and sensing can power biodegradable machines that work with natural environments, offering a sustainable alternative to conventional robotic materials and actuators.
(Nanowerk Spotlight) Robots are increasingly used in outdoor settings such as farms, forests, and conservation sites, where tasks involve sensing, monitoring, or gentle interaction with plants and soil. These environments highlight a basic problem in robotics. Most machines rely on durable materials such as plastics, metals, and electronic components that do not break down when left in the landscape. When a robot reaches the end of its service life or fails in the field, its remains can persist in soil or water. That persistence conflicts with the aims of environmental protection and long-term land management.
Efforts to address this issue have explored biodegradable plastics, gels, and natural fibers. Some materials lose strength when exposed to moisture or ultraviolet light. Others degrade too quickly or produce forces that are difficult to harness. These challenges have encouraged researchers to rethink how robots generate movement and respond to their environment. Instead of reproducing natural mechanisms with synthetic parts, engineers are examining whether the mechanisms in living systems could support robotic functions directly.
Plants present a straightforward case for this shift. They bend toward light, change shape as humidity rises or falls, alter posture through daily cycles, and react to touch with rapid movements. They do all of this without motors or batteries. Their actions come from growth, which lengthens tissues; internal water pressure, which changes cell shape; and structural layers that swell or shrink with moisture. These mechanisms respond to clear stimuli such as light, gravity, temperature, water, and mechanical contact. Each process follows consistent physical rules.
Advances in plant science now allow these movements to be measured at high resolution. Researchers can track bending angles, measure forces in the ranges of milli-newtons to newtons and record electrical signals that travel through plant tissues. Thin, flexible electrodes can attach to leaves without adhesives and without damaging the surface. These electrodes can stimulate movement with controlled electrical inputs or record the plant’s own electrical responses. These developments reveal that plant motion is not only an outcome of biological adaptation but also a reliable source of mechanical work.
This idea is the focus of a detailed perspective published in Advanced Science (“Plant Robotics for Sustainable and Environmentally Friendly Robots: Insights from Actuation Characteristics”). The paper introduces plant robotics, a field that uses living plants as actuators or sensors within robotic systems. It surveys how plants move, the stimuli that trigger those movements, and the forces and speeds plants can generate. It also reviews early devices that use plant-based actuation for gripping, locomotion, seed dispersal inspired movement, and environmental response.
Potential applications of plant robots utilizing physical movements. Through natural processes of growth and degradation, combined with functionalities analogous to robotic elements such as actuation and sensing, plants can fulfill diverse roles – including the structural formation, reinforcement of artificial buildings, object harvesting and capture, environmental greening, monitoring, and transportation. This multifunctionality, integrated into a self-sustaining life cycle, highlights the potential of plants as dynamic platforms for developing sustainable and eco-friendly robotic systems. (Image: Reproduced from DOI:10.1002/advs.202512896, CC BY) (click on image to enlarge)
The article organizes plant movement into three main categories. The first is growth. Growth produces slow but powerful movement as tissues lengthen over time. Radish sprouts extend at about 0.4 to 1.2 mm h⁻¹ and can exert forces around 3.2×10¹ mN. Dandelion growth can reach forces between 2 and 3 N. Bamboo culms show some of the fastest elongation known in plants, with peak rates above 1.0×10² cm per day. These values demonstrate that gradual extension can generate meaningful mechanical output.
The second category is turgor-based movement. Turgor pressure is the internal water pressure that keeps plant cells firm. When cells alter their water content, tissues bend or fold. Many species change leaf orientation between day and night. Common bean leaflets shift by about 89° over seven hours. Black locust leaves change orientation by roughly 102° over nine hours. Flowers such as Gentiana scabra open and close with temperature changes. Gentiana scabra petals bend by about 15° to 25° within sixty minutes at moderate temperatures.
Rapid turgor movements demonstrate the upper limit of plant-based motion. The Venus flytrap closes in 0.1 to 0.8 s and produces forces around 1.4×10⁻¹ N. Sensitive plants fold their leaflets within seconds after mechanical stimulation, generating about 1.0×10⁻² to 4.0×10⁻¹ mN. Some roots change direction when exposed to electrical fields. Both Venus flytrap and sensitive plants respond to electrical stimulation, which allows direct coupling to electronic controllers.
The third category is passive structural movement. These motions occur when plant tissues swell or shrink as they absorb or release water. The process does not require metabolic energy. Pinecone scales open in dry conditions and close as humidity rises. Their bending angles range from about 50° to 75°, and they can produce forces around 2.2 to 3.6 N. The Rose of Jericho contracts into a compact form during dry conditions and expands when hydrated, increasing surface area by about 88 percent within two to three hours. Horsetail spores extend by 2.5×10² to 3.5×10² µm within a few seconds as they absorb moisture.
Seed dispersal mechanisms expand this category further. Dandelion seeds descend at about 2.69×10¹ cm s⁻¹. Maple fruits spin as they fall, slowing descent through controlled rotation. Javan cucumber seeds glide with wings that carry them tens of meters. Sandbox tree seeds are launched at speeds between 1.3×10¹ and 7.0×10¹ m s⁻¹ through internal drying. Squirting cucumber seeds eject at about 2.0×10¹ m s⁻¹ when internal pressure releases. These cases show how structural design in plants can store and release energy in precise ways.
To control plant-based actuators, the paper reviews electrical interfaces. Early methods used direct wire insertion, which damaged tissues. Newer systems rely on ultrathin films made from conductive polymers or gold coated hydrogels. These films attach gently to leaves, maintain contact during movement, and allow stimulation or sensing across multiple days. They can drive Venus’s flytrap closure, detect leaf potentials during light changes, or map electrical signals across a structure.
The perspective then examines prototype devices that demonstrate plant-based actuation. One mobile robot uses the growth of radish sprouts to turn a wheel, moving at a speed close to the growth rate. A rack and pinion system converts growth into rotation. A light guided gripper uses phototropic bending of radish sprouts to lift a 0.1 g object. A Venus flytrap gripper closes on a 1 g object when electrically stimulated. Sensitive plants operate microfluidic valves by bending petioles. A water surface robot uses the folding motion of a sensitive plant to generate thrust at about 3.3×10⁻⁵ m s⁻¹. A pinecone structure forms a height changing platform that moves by about 49 mm with humidity.
These examples show the range of actuation that plants can support but also highlight several gaps. Data on plant mechanics remain scattered. Measurements of force, displacement, speed, elasticity, and density have not been compiled into a standard reference. Environmental conditions vary across studies, which limits reproducibility. T
he article identifies the need for systematic datasets, shared protocols, and improved modeling tools. It also notes the potential of chemical control through plant hormones, which regulate cell growth, and biostimulants, which influence metabolism. Genome editing could improve speed, repeatability, or environmental resilience.
Plant robotics offers a model in which robots operate on the same timescales as natural systems, rely on renewable energy, and break down after use. These systems could support environmental restoration, monitoring, or gentle manipulation in places where synthetic machines are impractical. By treating plant motion as a design tool rather than a biological curiosity, this field opens the possibility of machines that integrate into natural cycles rather than disrupt them.
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Jun Shintake (The University of Electrocommunications)
, 0000-0003-2442-2120 corresponding author
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