'One-of-a-kind' project: Sustainable artificial muscles could enable life-like movement in robots

"We hope the project will inspire other engineers to develop robotics with sustainability in mind.”
Mrigakshi Dixit
Representational image.
Representational image.

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Robotics holds great promise for humanity's future. And humans can expect more sophisticated robots to be integrated into more areas of life as technology advances in the coming years. 

Soft robotics is an emerging technology gaining traction in the scientific community. The primary goal of soft robotics is to achieve smooth and complex movement by mimicking the locomotion of soft bodies found in the environment.

In that pursuit, researchers at the University of Colorado Boulder have created a new type of robotic actuator, or "artificial muscle" to enable life-like movements. This one-of-a-kind project uses eco-friendly measures to create the actuator to protect the environment.  

“You could dispose of them in an industrial compost bin. We hope the project will inspire other engineers to develop robotics with sustainability in mind,” said Ellen Rumley, co-first author of the new study, in an official press release. 

'One-of-a-kind' project: Sustainable artificial muscles could enable life-like movement in robots
An "artificial muscle" made, in part, from material designed for biodegradable grocery bags.

The designing of artificial muscle

The innovation could help change robot structure from rigid to flexible. These can function similarly to human muscles and assist robots in bending their arms.

The team first created a prototype of artificial muscle known as Hydraulically Amplified Self-Healing ELectrostatic (HASEL) actuators in 2018. Their goal, however, was to make this soft robot feature completely sustainable. In this new study, they described the use of sustainable materials to create the novel artificial muscle, without compromising its performance when compared to the one designed in 2018. They were successfully able to naturally dissolve the prototype in soil over a few months. 

These actuators rely on fluid mechanisms that move in squishy pouches. The new HASEL actuator was created with "transformer oil inside plastic pouches." To allow electricity to pass through, these were partially covered with a thin layer of an electrical conductor. This mechanism allows the sac to be zipped, and as a result, the fluid moved from one end to the other. This also can be used to design a robotic limb.

The team experimented with various materials to replace the plastic pouches before settling on a biodegradable polyester blend commonly used in shopping bags. 

The actuators were designed so that the robots are "soft and flexible enough to bounce off walls or squeeze into tight spaces," according to the official statement. In the future, the artificial muscle could be programmed to move robotic arms and legs. According to Rumley, one promising application for these soft robots is to assist physically impaired individuals.

“The sustainability of the new materials system now opens up very interesting avenues for applications that require components designed for single- or short-term use, for example, in the area of food handling or medical applications,” said Christoph Keplinger, co-founder of Artimus Robotics, a Boulder-based company that develops and sells HASEL actuators.

The details have been published in the journal Science Advances.

Study Abstract:

Combating environmental pollution demands a focus on sustainability, in particular from rapidly advancing technologies that are poised to be ubiquitous in modern societies. Among these, soft robotics promises to replace conventional rigid machines for applications requiring adaptability and dexterity. For key components of soft robots, such as soft actuators, it is thus important to explore sustainable options like bioderived and biodegradable materials. We introduce systematically determined compatible materials systems for the creation of fully biodegradable, high-performance electrohydraulic soft actuators, based on various biodegradable polymer films, ester-based liquid dielectric, and NaCl-infused gelatin hydrogel. We demonstrate that these biodegradable actuators reliably operate up to high electric fields of 200 V/μm, show performance comparable to nonbiodegradable counterparts, and survive more than 100,000 actuation cycles. Furthermore, we build a robotic gripper based on biodegradable soft actuators that is readily compatible with commercial robot arms, encouraging wider use of biodegradable materials systems in soft robotics.

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