Biopolyester food packaging demonstrating biodegradable, artificial muscle technology [Image courtesy of MPI-IS, JKU and CU Boulder]
Researchers from Stuttgart, Germany; Linz Austria; and Boulder, Colorado, said artificial muscles could one day enable robots to function like living organisms. These muscles may create new possibilities for the way in which robots shape the world. However, their focus revolves around the environmental impact of these muscles for these robots.
The team includes researchers from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart, the Johannes Kepler University (JKU) in Linz and the University of Colorado, Boulder. They collaborated to design a fully biodegradable, high-performance artificial muscle, based on gelatin, oil and bioplastics. Used to animate a robotic gripper, this muscle demonstrates usefulness in single-use deployments. After use, they can be disposed of in municipal compost bins. Under monitored conditions, they fully biodegrade within six months, the researchers say.
The researchers published their findings in a paper titled “Biodegradable electrohydraulic actuators for sustainable soft robots.” Ellen Rumley, a visiting scientist from CU Boulder (working in robotic materials at MPI-IS), served as co-first author.
“We see an urgent need for sustainable materials in the accelerating field of soft robotics,” Rumley said. “Biodegradable parts could offer a sustainable solution, especially for single-use applications, like for medical operations, search-and-rescue missions, and manipulation of hazardous substances. Instead of accumulating in landfills at the end of product life, the robots of the future could become compost for future plant growth.”
About the HASEL artificial muscle
The researchers call their electrically driven artificial muscle “HASEL.” These oil-filled plastic pouches are partially covered by a pair of electrodes. Applying a high voltage across the electrode pair causes opposing charges to build on them. This generates a force between them that pushes the oil to an electrode-free region of the pouch.
According to the team, the oil migration causes the pouch to contract like a real muscle. The requirement for HASELs to deform is that the materials are electrical insulators and can sustain the high electrical stresses generated by charged electrodes.
To create a conductive, soft and fully biodegradable electrode, the team built its recipe on biopolymer gelatin and salts for direct casting onto HASEL actuators. David Preninger, co-first author for this project and a scientist at the Soft Matter Physics Division at JKU, said readily available components and accessible fabrication represented an important aspect of their research. Plus, it “serves as a building block for future biodegradable applications.”
Next, the team needed to find suitable biodegradable plastics. HASELs made from one specific material combination withstood 100,000 actuation cycles at several thousand volts, They achieved this without signs of electrical failure or loss in performance. The team aims to continue developing these to move toward a “paradigm shift in soft robotics.”
“By showing the outstanding performance of this new materials system, we are giving an incentive for the robotics community to consider biodegradable materials as a viable material option for building robots”, Rumley said. “The fact that we achieved such great results with bio-plastics hopefully also motivates other material scientists to create new materials with optimized electrical performance in mind.”
