Various materials are being researched at Empa, some of them with surprising properties. For example, there are elastomers that react to current and that contract or expand depending on the voltage applied. Two decades ago, a few researchers wondered what you could do with something like this. The result is almost ready to be marketed now – and could revolutionise electronic control elements.

The actuators developed by Gabor Kovacs (left) have the potential to make the leap from a research laboratory to a large-scale industrial application. Dorina Opris tailored the polymer films to meet specific needs. (Photo: Basil Stücheli/ETH Board)

Does something have to be set in motion? Nature relies on muscles, technology on motors; nature deforms, technology turns and screws. That could all be about to change, because researchers from Empa are in the process of bringing low-cost, mass-produced actuators to market maturity. They are based on technology that is basically simple, but rather secretive. Dielectric elastomers belong to the group of electroactive polymers and are materials that deform when electrical voltage is applied. Why they do this is still being researched at molecular level. In the last 20 years, scientists have learned how to “rein in” these materials in such a way that the deformation is very precise and can be finely manipulated. “It’s not that easy to create a linear movement,” says Pierangelo Gröning, member of the directorate and Head of the “Modern Materials and Surfaces” department. However, Empa has steadily progressed towards this goal over the years and been able to do so at comparatively deep or low voltages thanks to its know-how. Thus, the actuators developed by Gabor Kovacs have the potential to make the leap from a research laboratory to a large-scale industrial application.

The test actuators are like a soft stack of plastic in your hand, consisting of many thin plates. It might look unspectacular, but a lot of research work has gone into the ten-centimetre high stack. Kovacs recalls that a research programme was launched at Empa in 2000 with the aim of deforming mechanical structures with electrical signals. However, the mate-rials known at that time could hardly be used for specific applications. They did too little and were too expensive. However, believing firmly in the technology’s potential, they decided to move forward and set up the Functional Polymers department to develop these materials themselves. This makes actuators a “classic Empa case,” says Gröning, since they have their origins in materials research. What sets Empa apart is that the idea will then be refined “in this way in two different laboratories”. The engineering challenge was compounded by the optimisation of the material.

“Electroactive polymers have the potential to revolutionise electronic controls.” Pierangelo Gröning, member of the directorate and Head of the “Modern Materials and Surfaces” department

Dorina Opris is involved in the development of more suitable polymer films tailored to specific needs. The breakthrough was achieved thanks to her expertise. She modifies the elastomers that make up the films with dipoles, which makes them more “sensitive”. After modification, they become deformed at much lower voltages. She has also made the films “fit” for the special manufacturing process, in which they are applied to one another like in a 3D printer. This wet stack process also makes the Empa technology unique – automation has already been incorporated.

There are two manufacturing robots in the Kovacs research laboratory. One of the machines prints the finest film layers including stretchable electrodes, one on top of the other, so that a plastic plate about 0.5 millimetres thick slowly grows. This is then cut into small pieces in the other machine and stacked. As soon as electrical voltage is applied, each individual film is deformed marginally, and its thickness changes as well. The result would hardly be noticeable with a single layer, but there are more than 1000 foil layers in a stack. The effect is multiplied accordingly, and the actuators achieve movements from millimetres to centimetres that are even visible to the naked eye. The movement is completely silent, and the actuators compact and light. And reliable. The “artificial muscles” perform their movements thou-sands and millions of times without complaint. The principle can also be reversed: if the foils change thickness under pressure, this appears as an electrical signal.

One of the machines prints the finest film layers including stretchable electrodes, one on top of the other, so that a plastic plate about 0.5 millimetres thick slowly grows. This is then cut into small pieces in the other machine and stacked.

On the one hand, Kovacs envisages that they can be used in the human body as “auxiliary muscles”. However, he also sees great potential in the con-sumer goods industry. Human-machine interaction could be completely transformed by actuators. Imagine a flat user interface that reacts by tactile rather than visual means. Buttons are created as required, and a relief is constantly changing. This is of interest to the car industry, for example. “Morphing cockpits will be standard in cars in ten years,” predicts Kovacs. CTsystems, a business which grew out of his tenacious research work, will put this into practice and bring it onto the market.