Actuators are the "muscles" of robots -- the moving parts. Researchers at Harvard are working to build actuators that are more like, well, muscles.

The advantage of a muscle-like actuator is that it is soft, malleable and more resilient. Engineers have designed robots in all sorts of shapes and out of all sorts of materials -- origami robots, bumble bee robots, inchworm robots.

But most soft-bodied robots remain small and relatively weak. Big and powerful robots are mostly still hard-bodied and angular. As such, they pose a danger to themselves as well as humans. If robots are to integrate seamlessly with humans, they need to become more human-like.

A team of researchers set out to build an actuator inspired by the human bicep.

The scientists, led by George Whitesides, a professor at Harvard's Wyss Institute for Biologically Inspired Engineering, designed a soft-bodied actuator with small, hollow honeycomb-like chambers of air. Similar designs have been built and actuated by pressurized air, but Whitesides and his team designed theirs to contract by buckling as air is sucked out by a vacuum.

They dubbed the technology VAMPs -- short for vacuum-actuated muscle-inspired pneumatic structures.

Researchers recalled their efforts in a new paper, published this week in the journal Advance Materials Technologies.

"Having VAMPs built of soft elastomers would make it much easier to automate a robot that could be used to help humans in the service industry," first author Dian Yang, a former Harvard grad student, now a postdoctoral researcher, said in a news release.

"There are other soft actuators that have been developed, but this one is most similar to muscle in terms of response time and efficiency," added Whitesides.

The actuator is not only soft, it also avoids the use of pressurized gas.

"It can't explode, so it's intrinsically safe," said Whitesides.

"These self-healing, bioinspired actuators bring us another step closer to being able to build entirely soft-bodied robots, which may help to bridge the gap between humans and robots and open entirely new application areas in medicine and beyond," concluded Donald Ingber, the founding director of the Wyss Institute.