A joint effort from scientists at universities across the globe have developed a fully biodegradable, high-performance artificial muscle, a development heralded as a step towards sustainability becoming a lasting trend in the field of soft robotics.
At Max Planck Institute for Intelligent Systems in Stuttgart (MPI-IS), Germany, Johannes Kepler University (JKU) in Linz, Austria, and University of Colorado Boulder (CU Boulder) in the US, the teams collaborated to make a 100% biodegradable, high performance artificial muscle based on gelatine, oil, and bioplastics.
The electrically driven artificial muscle created was dubbed HASEL. HASELs are oil-filled plastic pouches that are partially covered by a pair of electrical conductors called electrodes. Applying a high voltage across the electrode pair causes opposing charges to build on them. This generates a force between them that pushes oil to an electrode-free region of the pouch. This oil migration causes the pouch to contract, similar to a real muscle. The key requirement for HASELs is that the materials making up the plastic pouch and oil are electrical insulators, which can sustain the high electrical stresses generated by the charged electrodes.
The muscle’s use was demonstrated by using it on an animated robotic gripper, which was used to pick up several items, including irregular shaped items like vegetables. It’s thought the muscle could be especially useful in single-use deployments such as for waste collection, and at the end of life, they can be disposed in the very compost bins they work within, where under monitored conditions, they fully biodegrade within six months.
Building a conductive, soft, and fully biodegradable electrode was one of the main challenges of this research. Researchers at JKU created a recipe based on a mixture of biopolymer gelatine and salts that can be directly cast onto actuators. Next, engineers had to find suitable bioplastics with good material compatibility with gelatine electrodes and sufficient electrical insulation. HASELs made from a specific material combination were even able to withstand 100,000 actuation cycles at several thousand Volts without signs of electrical failure or loss in performance.
Artificial muscles are a progressing technology that are poised to enable robots to function more like living organisms. This not only allows robots greater movement, but can even be implemented in assistive wearable devices, to rescue robots that need to navigate difficult terrain, and most importantly for this development, can minimise its environmental impact after use.
With the push for net zero and the demand for sustainability becoming ever more ubiquitous, especially as the use of robotics increase, developments like this a paradigm shift.
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