In search of the perfect polymer: the mission of Dorina Opris

When the solution is in the "right chemistry": the work of a Swiss scholar on dielectric polymers starts from the synthesis of new materials

Polymers: the search for Dorina Opris
Dr. Dorina Opris and the TRANS project for the synthesis of new dielectric polymers (Photo: Marion Nitsch/Lunax/EMPA)

Artificial muscles and eyelids, flexible speakers, fabrics that come to life: these are some of the possible applications of electroactive polymers, particular chemical compounds capable of changing shape and size when subjected to electrical stimuli.

These polymers are among the so-called smart materials, and are considered absolutely among the most promising: they can find use as non-conductive layers in stacked transistors and in new generation sensors, and have the potential to revolutionize consumer electronics also from a point of view ofenvironmental impact.

in Swiss Federal Laboratories of Materials Science and Technology (EMPA), the team of Dr Dorina Opris is working on the synthesis of new polymers for transducers.

What we are trying to obtain is an extremely thin, elastic, sensitive to low voltage and printable polymer. The perfect polymer to use as an ultra-thin layer in next generation actuators and sensors.

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Dr. Dorina Opris and a PhD student from her team in the Swiss laboratories of EMPA (Photo: Marion Nitsch/Lunax/EMPA)

TRANS, the multidisciplinary project at EMPA

The project by Dr. Dorina Opris, director of the Functional Polymeric Materials research group at EMPA, was awarded theERC Consolidator Grant, a prestigious five-year grant awarded by the European Research Council.

La Research it will last until 2026 and is called TRANS, which is an acronym for “Synthesis of new stimuli-responsive dielectric polymers and their applications in powerful transducers”.

The purpose of the Opris is to develop new polymers capable of transforming energy, for example by converting the mechanical one into electric or vice versa, and test them on different practical applications.

These new materials can reversibly change their shape when subjected to an electric field, generate electricity when manipulated, convert thermal energy into electricity, and even accumulate energy in the form of batteries.

According to Dorina, these polymers “have the potential to revolutionize several applications, including actuators, sensors, artificial muscles, soft robotics, energy production and storage, flexible electronic components and solid-state refrigeration".

A key aspect of this project is the sustainability: what you intend to develop is a series of printable, environmentally friendly inks, scalable and simple to apply, which can be the active ingredients of electronic devices of the near future.

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Dr. Dorina Opris demonstrates decolorizing liquid in the EMPA laboratories (Photo: Marion Nitsch/Lunax/EMPA)

Electroactive polymers: not just electronics

Almost a hundred years have passed since the synthesis of the electret, the first piezoelectric polymer: then, to obtain a material that generated an electric field, carnauba wax, beeswax and rosin were combined.

Today, in Swiss Federal Laboratories of Materials Science and Technology, the Dorina Opris team works with a completely different kind of ingredients, and aims to create more functional materials than the first piezoelectric polymers.

Unlike piezoelectric materials, which are mostly used today to generate small amounts of energy, i electroactive polymers can withstand very significant deformations, up to 380 percent.

They also show very fast response times and can be adapted to a large variety of applications, also due to the fact that they are made from raw materials relatively cheap.

These polymers also have ahigh resilience, that is, they are able to regain their original shape after being deformed. An excellent example of this property is in polymeric, or artificial muscles, based actuators liquid crystal elastomer, whose functioning is based precisely on shape memory.

The new dielectric polymers can stretch in response to electrical voltage and can be used as ultra-thin layer in the actuators, but also for other components: for example, in the field of digital mechatronics, in consumer electronics and also in the production of energy from renewable sources.

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TRANS multidisciplinary research aims to synthesize new dielectric polymers (Photo: Marion Nitsch/Lunax/EMPA)

The winding and unedited roads of chemistry

Before arriving at Federal Polytechnic of Zurich, Opris studied organic chemistry at Babeş-Bolyai University, Cluj, Romania, via the Freie Universität Berlin. The path that you have led to the synthesis of new polymers for technological applications which are purely engineering required time and collaboration.

The expertise that led to the TRANS project is also the result of the work of several EMPA colleagues. Among them the engineer Gabor Kovacs, who led the development of stacked actuators with expandable silicone discs for several years.

"Instruments that measure how actuators react in different electric fields were developed by them”, says Opris. “We were at the forefront of this issue, and this was extremely helpful to my research".

La chemistry, however, works on a more hidden level: instead of wondering how to print these components, the Dorina team will take care of the development of new materials suitable for the purpose. A chemistry it is up to the synthesis of new polymers.

The work of the Opris team has already produced encouraging results, managing to print capacitor layers without the use of solvents and synthesizing a silicone polymer capable of reacting to a voltage as low as 300 volts.

A PhD student has also recently produced a piezoelectric elastomer which, in voltage, shows a much higher electrical response than other polymers in use today.

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Dielectric polymers, the research of Dorina Opris
What we intend to synthesize is a new solvent-free printable polymer that is environmentally friendly and scalable (Photo: Marion Nitsch/Lunax/EMPA)

The perfect polymer: if “the right chemistry” is enough

The perfect polymer profile it is far from simple to achieve: it must be as thin as possible, with the long-term goal of making many layers in a thickness of 10 micrometres. It must also be easily manipulated, sensitive to low voltages and at the same time very robust.

Above all, Dr. Opris explains, it has to be printable without solvents. "Solvents can damage the polymer layer, furthermore the material would need a long drying process to avoid the emission of harmful vapors”. The idea is to "try to do without solvents, just with the right chemistry".

Among the most promising compounds in this sense are i silicones, which is also being worked on in the EMPA laboratories. These polymers are simple to synthesize, and their filaments have a very malleable chemical structure, which makes them suitable for functionalized with polar groups.

What makes it particularly ambitious this research project is rendered by the Opris with an evocative image: “You can imagine these silicones as containers full of snakes that want to move all the time".

Polar groups have a double effect: first they make these “snakes of molecules' more sensitive to electric fields, so they respond to weaker voltages, then act as a kind of glue between molecules. This stiffens them, reducing their elasticity.

The challenge is to fine-tune the perfect balance between these two effects, and to obtain that the transition from the solid to the elastic state takes place at low temperatures. This will allow you to use the tech the temperature technology, a fundamental characteristic for future practical applications.

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Dr Dorina Opris at work in the EMPA laboratories: her research has been awarded an ERC Consolidator Grant (Photo: Marion Nitsch/Lunax/EMPA)