(CN) — Scientists have developed a type of soft-bodied spongy robot that doesn’t require any complex hardware or electricity to move about, as it’s powered entirely by lights and magnets.
Their unique creation is comprised of 90% water and made by molding hydrogels over a ferromagnetic nano-wire skeleton without any of the heavy machinery typically found in robots.
Activated by light, a nearby rotating magnetic field determines the bot’s movements, allowing it to climb hills and transport cargo at human speeds — a marked improvement over an earlier version.
The team from Northwestern University in Illinois say their invention is ideally suited for work in aquatic environments and could even be shrunk down later to deliver bio-therapeutics to individual cells and tissues. The team published their findings Wednesday in the journal Science Robotics.
“Having simply ‘materials’ rather than complicated devices that can behave like robots and emulate the behaviors of living creatures — walking, crawling, picking up and transporting things, swimming, recognizing objects and taking some action, changing shape — could create groundbreaking imaginative technologies in our future. This would indeed be matter with surprising life-like properties which we have labeled ‘robotic soft matter,’” said the study’s co-author Samuel Stupp, professor of engineering at Northwestern University, in an email.
To drive the robot, a nearby magnetic field is programmed with specific sequences which pull its nanowire frame along the desired path, allowing it to snake cargo through narrow passages and over complex terrain. Once at its destination, the robot inverts its shape to allow its payload to gently slide off, or it can perform a spinning maneuver to dislodge stickier cargo.
“We were excited to find that we could create soft materials that could respond to low energy inputs of light and magnetic forces and made them walk on the timescale of human steps (about one step per second),” Stupp explained. “We were also excited to mathematically predict the behavior of the new materials using physical theories and thus were able to program the materials to follow specific trajectories.”
The robot’s unique properties are a result of the chemical synthesis used in its design. A hydrogel “skin” is programmed to repel water when exposed to light, causing the robot to bend and contort itself into a desired shape.
The team also found that it responds rapidly to rotating magnetic fields, which allow it to be driven around somewhat like a toy car by programming specific magnetic sequences. After the lights go out, the robot returns to an inert flat shape, but can be reactivated anytime by turning the light back on.
The researchers also experimented with different molecular photo switches to tune how the robot responds to light. Some of the materials they tried can maintain their bending shape under variable light conditions, while others revert to a flattened shape when exposed to excessive light levels. These alternating levels of stiffness and shapelessness are what allow the device to walk at the desired speed and gait.
“The design of the new materials that imitate living creatures allows not only a faster response but also the performance of more sophisticated functions,” Stupp noted in a related statement. “We can change the shape and add legs to the synthetic creatures, and give these lifeless materials new walking gaits and smarter behaviors. This makes them highly versatile and amenable to different tasks.”
This research draws on previous work by Stupp to design soft robotic matter that mimics living sea creatures. Previously, the best material developed required minutes to bend and could only take one step every 12 hours. This version takes one step per second, so the improvements are substantial.
The team has high hopes for their creation and believe these spongy aquatic robots could one day be used in fields such as chemical engineering, environmental studies or as an intelligent biomaterial for advanced medical procedures such as drug delivery. They also believe these devices hold greater promise when used in tandem to achieve complex movements.
“We are very excited about the potential of miniaturizing these materials for the functions described above,” Stupp said. “However, we also believe there is the potential to design new soft robotic materials of larger size to carry heavier cargo or move greater distances. When scaled down to smaller sizes, billions of ‘microrobots’ could be designed to perform collective tasks similar to the cells in a tissue or bacteria in a macroscopic colony.”