Picture a robot. What do you see? A rugged, steel-clad machine built to transcend living beings’ organic fragility? Unfortunately, this very quality now threatens to drown the planet in extremely durable e-waste. What if, instead, our increasingly prevalent machines were designed to decay and disappear—like life does?
For a study in Science Advances, researchers crafted a robotic arm, and a joysticklike controller to operate it, from pork gelatin and plant cellulose—materials sturdy enough to function yet delicate enough to degrade in backyard compost. After testing, both origamilike structures disintegrated in soil within weeks.
Biodegradable robotics often falls under the umbrella of soft robotics, which draws inspiration from nature’s more pliable creations. “The field originated from materials science and chemistry rather than conventional robots that come from mechanical engineering,” says materials scientist Florian Hartmann of the Max Planck Institute for Intelligent Systems in Stuttgart, Germany. But a lot of early soft robotics prototypes still relied on synthetic polymers that linger as pollution.
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Pingdong Wei, a materials scientist working with natural polymers at Westlake University in Hangzhou, teamed up with his friend Zhuang Zhang, a robotics engineer now at Fudan University in Shanghai, to assemble robots for the new study. Wei had long been intrigued by robotics, Zhang recalls, and raised the idea of creating a robot himself. “That’s when I thought, Why not use the materials he works with to build one?”
They started with cellulose layers derived from cotton pulp, then added glycerol for flexibility and dried the layers for strength. “Cellulose is also cheap and easy to assemble,” Wei says. To build sensors, the researchers used a conductive gelatin extracted from pork, in which the flow of ions changes when the material is stretched, bent or pressed. They then folded the flat films and sensors into 3D structures.
Wei and Zhang found that the controller and robotic arm stood up to both heavy use and a week of inactivity. Finally, they buried them both in a 20-centimeter-deep hole near their campus. Within eight weeks the machines were almost entirely gone.
“The way the researchers were able to engineer something so rigid yet so soft is impressive,” says robotics engineer Ellen Rumley, who is also at the Max Planck Institute for Intelligent Systems. Neither Rumley nor Hartmann was involved in the study.
Wei and Zhang envision bots like these handling hazardous waste and then dissolving; they also propose robots that aid surgeries and then safely break down inside the body. But it’s important to note that the technology is in very early stages.
“If we truly want to have a sustainable robot that goes outside in nature,” Hartmann says, “we also need to think of electronics or power supplies, or even batteries, that are biodegradable.”
