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New Muscle-Inspired Actuators Hold Potential to Build Safer, Soft-Bodied Robots

Robots should be safer and softer in order to make them more cooperative and execute tasks in close contact with humans. 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 (FAS), along with his team, has created a new actuator that moves like human skeletal muscles by using vacuum power for automating soft, rubber beams.

In this image, VAMPs are shown actuated and cut open in cross section. The cross section shows the inner chambers that collapse when vacuum is applied. (Credit- Wyss Institute at Harvard University)

These actuators are soft and shock absorbing similar to real muscles, and do not pose any danger to their surroundings or the human beings working along with them or the future robots containing them. This study was published in the June 1 issue of the Advanced Materials Technologies journal.

Functionally, our actuator models the human bicep muscle. There are other soft actuators that have been developed, but this one is most similar to muscle in terms of response time and efficiency.

George Whitesides, Director of the Kavli Institute for Bionano Science and Technology at Harvard University

Whiteside and his colleagues used vacuum to reduce the volume of the actuator and make it buckle, a step that was a novel approach in its design. The research group exploited the mechanical instabililty caused by bucking to create vacuum-actuated muscle-inspired pneumatic structures (VAMPs) as opposed to conventional engineering where bucking is considered as a point of failure. The earlier version of soft actuators used pressurized systems that increase in volume. Conversely, VAMPs are able to imitate true muscle as they contract and hence, can be used in confined places and for various other purposes.

This new actuator consists of soft rubber or 'elastomeric' beams and features tiny, hollow air chambers similar to a honeycomb. The application of vacuum makes these chambers to collapse and the actuator to contract. This, in turn, generates movements. It is possible to customize the internal honeycomb structure in order to facilitate twisting, bending, linear and combinatorial movements.

"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," said Dian Yang, main author of the study and a graduate researcher pursuing his doctorate in Engineering Sciences at Harvard at the time of the study, and is currently a Postdoctoral Researcher.

The research group believes that constructing robots with VAMPs would help old and disabled people, to deliver goods, serve food, and execute various other service related tasks. Another advantage is human operators can work closely with soft robots in the same space, thus creating safer and faster production lines and facilitating quality control.

Owing to its simplicity, this kind of actuation is easy to manage even though a complicated control system has not been designed for VAMPs. VAMPs contract upon application of vacuum. The actuators can be integrated into a tethered or untethered system based on the performance and environmental requirements. Also, VAMPs are engineered to avoid failure. The team demonstrated the ability of VAMPs to function continuously even after subjected to damage with a 2 mm hole. VAMPs fail safely when the system damage is significant.

It can’t explode, so it’s intrinsically safe.

George Whitesides

Lack of vacuum pressure in VAMPs would make the actuator stationary while other actuators powered by combustion or electricity could harm human operators or their surroundings .

"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," said Donald Ingber, M.D., Ph.D., Wyss Founding Director and the Professor of Bioengineering at Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS) and Judah Folkman Professor of Vascular Biology at Harvard Medical School and the Boston Children’s Hospital Vascular Biology Program.

Patents regarding this and other related inventions have been filed by Harvard’s Office of Technology Development, and Soft Robotics, Inc., a startup established in 2013 and cofounded by Whitesides, was given the license for the soft actuator technology. The company is creating robotic grasping systems for preliminary applications like packing and picking in unstructured places, for instance, handling vegetables and fruits in produce distribution warehouses.

In the longer term, it is possible to exploit the soft actuator technology to develop products for biomedical applications.

Apart from Whitesides and Yang, other authors of the study include Mohit S. Verma, Ph.D.,(FAS); Ju-Hee So, Ph.D., (FAS); Bobak Mosadegh, Ph.D., (Wyss, FAS); Christoph Keplinger, Ph.D., (FAS); Benjamin Lee (FAS); Fatemeh Khashai (FAS); Elton Lossner (FAS), and Zhigang Suo, Ph.D., (SEAS, Kavli Institute).

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