September 20, 2020

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This machine only moves with artificial muscles

A miniature submarine that works without a motor, fuel and electricity? This works in the initial stages, as an alternative drive concept from ETH Zurich. It relies on artificial muscles with shape memory that derive their energy from temperature differences.

The mini submarine, which researchers at Zurich have produced with the 3D printer, looks unassuming. But it could be the first step to an alternative drive that does not require external energy. The plastic vehicle is only 7.5 cm long and there are two 5 cm long paddles on both sides. The special thing about the construction are the drive elements, which are mounted between the fuselage and the paddle. At its heart are plastic muscles with shape memory, with which the boat can paddle without any motor, fuel or electricity.

Artificial muscles expand when the temperature changes

For a paddle stroke, the boat is dependent on a change in temperature. When the water warms up, the stripe-shaped muscles expand until they press on a lifting element. The lifting element folds down and triggers a paddle stroke. The boat moves a little bit forward. A technology that could eventually be used in diving robots?

The researchers have at least succeeded in making complex movements. For example, a boat drove a paddle stroke, dropped a coin and then did a paddle stroke backwards. How does the sequence of actions work? About the dimension of the plastic muscles. Thinner plastic strips react faster than thicker ones.

The researchers then have to reset the lifting elements by hand. How could a muscle contract without having to rely on a temperature change like every paddle stroke length? The researchers don’t explain that.

But ETH professor Kristina Shea is convinced: “The focus of our work is that we have developed a new and promising drive system that is completely 3D-printed and does not need an external power source.” It is conceivable that the artificial muscles do not depend on the water temperature react, but to the acidity or salinity of the water.

Not only in Switzerland, but also in the USA, research is carried out on artificial muscles. Researchers at the Massachusetts Institute of Technology (MIT) are inspired by origami, the Japanese art of paper folding. The engineers fold a plastic film into an accordion-like skeleton and seal it in a plastic bag. A pump creates a vacuum, the skin and skeleton contract and produce a lifting movement.

The system weighs only 2.6 g, but is strong enough to lift a 2.6 kg weight. If air flows back into the bag, the system expands again. A deformation that returns to its original state: this principle also works with hair-fine wires that should perform precise and powerful movements in hand prostheses.