An international team of researchers from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart, Germany, the Johannes Kepler University (JKU) in Linz, Austria, and the University of Colorado (CU Boulder), Boulder, USA, have brought sustainability to the forefront of soft robotics.
Together, they developed a fully biodegradable, high-performance artificial muscle made of gelatin, oil, and bioplastics. The scientists showcased the potential of this innovative technology by using it to animate a robotic gripper, particularly beneficial for single-use applications such as waste collection. These artificial muscles can be disposed of in municipal compost bins and fully biodegrade within six months under monitored conditions.
Ellen Rumley, a visiting scientist from CU Boulder working in the Robotic Materials Department at MPI-IS and co-first author of the paper, emphasizes the importance of sustainable materials in soft robotics:
“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.”
Developing Biodegradable HASEL Artificial Muscles
The researchers created an electrically driven artificial muscle called HASEL (Hydraulically Amplified Self-healing Electrostatic Actuators). HASELs are oil-filled plastic pouches partially covered by a pair of electrical conductors called electrodes. When a high voltage is applied across the electrode pair, opposing charges build up, generating a force that pushes oil to an electrode-free region of the pouch. This oil migration results in the pouch contracting, similar to a real muscle. For HASELs to deform, the materials used for the plastic pouch and oil must be electrical insulators capable of sustaining the high electrical stresses generated by the charged electrodes.
A key challenge was developing a conductive, soft, and fully biodegradable electrode. Researchers at JKU created a recipe using a mixture of biopolymer gelatin and salts that could be directly cast onto HASEL actuators.
David Preninger, co-first author for this project and a scientist at the Soft Matter Physics Division at JKU, explains:
“It was important for us to make electrodes suitable for these high-performance applications, but with readily available components and an accessible fabrication strategy.”
Electrical Performance and Biodegradable Plastics
The next hurdle was identifying appropriate biodegradable plastics. Engineers typically prioritize factors such as degradation rate and mechanical strength over electrical insulation, a requirement for HASELs that operate at several thousand volts. However, certain bioplastics demonstrated good material compatibility with gelatin electrodes and sufficient electrical insulation.
One specific material combination allowed HASELs to withstand 100,000 actuation cycles at several thousand volts without electrical failure or performance loss. These biodegradable artificial muscles are electromechanically competitive with their non-biodegradable counterparts, promoting sustainability in artificial muscle technology.
Ellen Rumley elaborates on the impact of their research:
“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. 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.”
Future Prospects and Applications
The development of biodegradable artificial muscles opens new doors for the future of robotics. By incorporating sustainable materials into robotic technology, scientists can reduce the environmental impact of robots, particularly in applications where single-use devices are prevalent. The success of this research paves the way for the exploration of more biodegradable components and the design of entirely eco-friendly robots.
Potential applications for biodegradable soft robots extend beyond waste collection and medical operations. These robots could be used in environmental monitoring, agriculture, and even consumer electronics, reducing the burden on landfills and contributing to a circular economy.
As the research continues, the team plans to further refine the materials and processes used in creating biodegradable artificial muscles. By collaborating with other experts in material science and robotics, they aim to develop new technologies that will propel the field of sustainable soft robotics forward. researchers hope to encourage the adoption of biodegradable materials in various industries, thereby fostering a more eco-conscious approach to technology development.
The groundbreaking work of this international research team represents a vital step towards a more sustainable future for soft robotics. By demonstrating the viability and performance of biodegradable artificial muscles, they are paving the way for further advancements in green technology and inspiring the robotics community to consider sustainable alternatives for their creations.