Self-powered Mobile Polymers Convert Ultraviolet Light Into Motion
New materials that directly convert ultraviolet light into motion without the need for electronics or other traditional methods have been developed by an international group involving Inha University, University of Pittsburgh and the Air Force Research Laboratory, building upon their previous research.
One of the impediments to developing miniaturized, “squishy” robots is the need for an internal power source that overcomes the power-to-weight ratio for efficient movement.
Other investigations have proposed the use of ambient energy resources such as magnetic fields, acoustics, heat and other temperature variations to avoid adding structures to induce locomotion.
However, co-author Dr. M. Ravi Shankar explains, light is more appealing because of its speed, temporal control and the ability to effectively target the mechanical response. For the material, the group zeroed in on monolithic polymer films prepared from a form of liquid crystalline polymer.
“Our initial research indicated that these flexible polymers could be triggered to move by different forms of light,” Dr. Shankar explained. “However, a robot or similar device isn’t effective unless you can tightly control its motions. Thanks to the work of Dr. White and his team at AFRL, we were able to demonstrate directional control, as well as climbing motions.”
Self-powered Mobile Polymers
According to Dr. Wie, the “photomotility” of these specific polymers is the result of their spontaneous formation into spirals when exposed to UV light. Controlling the exposure enables a corresponding motion without the use of external power sources attached directly to the polymer itself.
“Complex robotic designs result in additional weight in the form of batteries, limb-like structures or wheels, which are incompatible with the notion of a soft or squishy robot,” Dr. Wie said. “In our design, the material itself is the machine, without the need for any additional moving parts or mechanisms that would increase the weight and thereby limit motility and effectiveness.”
In addition to simple forward movement, Dr. White and the collaborative team were able to make the polymers climb a glass slide at a 15-degree angle.
While the flat polymer strips are small, approximately 15mm long and 1.25mm wide, they can move at several millimeters per second propelled by light. The movement can be perpetual, as long as the material remains illuminated.
“The ability for these flexible polymers to move when exposed to light opens up a new ground game in the quest for soft robots,” Dr. Shankar said.