UEC researchers have developed tiny robots powered by the natural growth of plants. These “plant robots” move and grip without motors or batteries, offering a sustainable new approach to robotics.

Robots usually need heavy hardware—motors, gears, batteries—to move and grasp. Jun Shintake and colleagues at took a different route: let plants do the work. Because plants convert light into chemical energy and push outward as they grow, the authors treated growth itself as an actuator with a built-in power source. They first quantified what that “actuator” can do using radish sprouts: how far a sprout elongates over hours, how much force it can exert, and how lighting conditions tune both. The data showed steady millimeter-scale displacement (up to ~76 mm within ~55 hours) and peak forces near sprouting (up to ~97.5 mN), with growth and force following simple models that engineers can use for design.

Building on these results, the team created two proof-of-concept “plant robots.” The first is a palm-sized rolling robot: four sprouts are arranged around a circular frame like soft, slow “pistons.” As the longest sprout pushes against the ground, the robot rotates until the next sprout takes over, producing continuous roll-and-go motion. In tests, it traveled 14.6 mm at an average of 0.8 mm per hour in the dark (slightly less under illumination due to water loss), and its path closely matched predictions from the growth model—evidence that plant actuation can be engineered, not just observed.

The second device is a light-guided gripper. Here, each sprout acts as a finger that bends toward LEDs (phototropism). Switching inner LEDs on makes the “fingers” curl inward to grasp; illuminating outer LEDs reverses the bend to release. The gripper successfully picked up and placed a 0.1-gram object, generating ~9.8 mN of holding force. Notably, using multiple sprouts in parallel reduced variability, smoothing out differences between individual plants and yielding more reliable performance—another practical lesson for design.

Why does this matter for innovation? First, sustainability: these robots run on water and light, use biodegradable components, and avoid propellers or hard edges that can damage their surroundings. Second, safety and cost: soft, slow, and light by nature, plant robots are inherently safe around people and delicate objects and can be fabricated with simple tools. Third, new use-cases: long-duration, low-disturbance tasks—environmental monitoring, agricultural sensing, gentle handling of sensitive samples—where silence, softness, and ultra-low power are benefits, not bugs.

Lead author Jun Shintake explains: “Plants grow by converting light into chemical energy. We realized this growth could itself be used as a gentle actuator for robots. Our goal is to create sustainable machines that are safe, biodegradable, and work in harmony with their environment.”

This study shows how natural growth can be reframed as a design resource, turning the quiet, steady force of plants into a new approach for robotics.