A soft actuator inspired by the human bicep muscle could pave the way for soft-bodied robots that are safer and more dynamic than their rigid counterparts.
Developed by a team at the Wyss Institute at Harvard University, the shock-absorbing, soft actuators allegedly pose no danger to their environment, humans working alongside them, or the potential future robots equipped with them. The team said these soft actuators could lead to better assistive robots, for example, that could serve food, deliver goods and perform other tasks related to the service industry.
“Functionally, our actuator models the human bicep muscle,” said team leader George Whitesides, Ph.D., a Core Faculty member at Harvard’s Wyss Institute for Biologically Inspired Engineering and the Woodford L. and Ann A. Flowers University Professor of Chemistry and Chemical Biology in Harvard University’s Faculty of Arts and Sciences. “There are other soft actuators that have been developed, but this one is most similar to muscle in terms of response time and efficiency.”
The team said it took an unconventional approach to its design, relying on vacuum to decrease the actuator’s volume and cause it to buckle. We’ll let them explain:
“While conventional engineering would consider bucking to be a mechanical instability and a point of failure, in this case the team leveraged this instability to develop VAMPs (vacuum-actuated muscle-inspired pneumatic structures). Whereas previous soft actuators rely on pressurized systems that expand in volume, VAMPs mimic true muscle because they contract, which makes them an attractive candidate for use in confined spaces and for a variety of purposes.
VAMPs are modeled after the human bicep in terms of response time and efficiency. (Photo Credit: Wyss Institute at Harvard University)
“The actuator – comprising soft rubber or ‘elastomeric’ beams – is filled with small, hollow chambers of air like a honeycomb. By applying vacuum the chambers collapse and the entire actuator contracts, generating movement. The internal honeycomb structure can be custom tailored to enable linear, twisting, bending, or combinatorial motions.”
Although a complex control system has not yet been developed for VAMPs, the team said this type of actuation is easy to control due to its simplicity: when vacuum is applied, VAMPs will contract. They could be used as part of a tethered or untethered system, depending on environmental or performance needs.
Whitesides also said VAMPs are designed to prevent failure – even when damaged with a 2mm hole, the team showed that VAMPs will still function. In the event that major damage is caused to the system, it fails safely. Actuators powered by electricity or combustion could cause damage to humans or their surroundings, loss of vacuum pressure in VAMPs would simply render the actuator motionless.
“It can’t explode, so it’s intrinsically safe,” said Whitesides.