1/2016

Light generates movement

TUT has embarked on the development of light-controlled materials. The idea is to produce mechanical movement by changing the length and thickness of these materials, thus enabling the creation of microrobots and tunable optical materials. At best, this new material concept could one day be utilized in several fields and across disciplinary borders.

Arri Priimägi

 

“I am a dedicated fan of fundamental research, and the force that drives me the most is scientific curiosity. This should be supported in the university world, as it spawns technological advancement, says Academy Research Fellow, Assistant Professor Arri Priimägi from TUT’s Department of Chemistry and Bioengineering.

 

Without light, we would not have the fast Internet connections enabled by optical fibres, we would not have home entertainment as we know it today, and we would also lack many modern medical tools. New lighting solutions, such as LED lights, along with solar cells, are key light-based technologies whose significance is only about to grow in the years to come.

“Last year was proclaimed as the International Year of Light. Also, technological gurus have predicted that the 2000s will become the century of light and that light-based technologies will revolutionize our lifestyle as we know it, says Academy Research Fellow, Assistant Professor Arri Priimägi from TUT’s Department of Chemistry and Bioengineering.

Photonics, i.e. the science of light, studies how light can be produced, manipulated and detected. In practice, photonics is also often dubbed optics.

Light changes material properties

Who? Arri Priimägi
(born in Tallinn, Estonia, in 1980)

  • Most important degrees
    • Doctor of Science in Technology, Helsinki University of Technology, 2009
    • Master of Science in Technology, Tampere University of Technology, 2004
  • Most important positions and appointments
    • Assistant Professor, Academy Research Fellow, Tampere University of Technology, Department of Chemistry and Bioengineering, 09/2014–
    • International Research Fellow, Politecnico di Milano, Italy, 12/2013–08/2014
    • Researcher, Aalto University, 01/2013–11/2013
    • Post-doc researcher, Chemical Resources Laboratory, Tokyo Institute of Technology, Japan, 12/2010–12/2012
    • In his free time Priimägi plays bass in the pop rock band Vaihde. ”You’ve never heard of Vaihde? Look us up on Spotify or check us out live!”
 

Priimägi is heading a new five-year ‘Tunable Photonic Structures via Photomechanical Actuation’ project for which he received a 1.5 million euro funding from the European Research Council.

Consisting of chemists and physicists, Priimägi’s research group studies and develops functional light-controlled materials whose length and thickness can be altered to generate mechanical movement.

Certain properties of functional materials can be changed with specific external stimuli. In this case, the stimulus is light.

“Light is a convenient stimulus for designing functional materials in that it is easily available, cheap and environmentally friendly. The materials can be remotely controlled with a laser or a LED, for example. The properties of light, such as colour, intensity, polarization or the duration of a light pulse, can be controlled with great accuracy. Therefore, many things can be done with light that cannot be done with other stimuli,” Priimägi continues.

The aim is to develop techniques and methods for managing light-controlled changes in the length and thickness of polymeric substrates and thin films, respectively.

The secret lies in small molecular switches

“The light control is enabled by molecular switches, which are molecules approximately a single nanometre in length. A human hair could fit roughly 50,000 of them side by side. Light allows us to tune the molecules so that they transform and change in length.”

The molecular switches are very intriguing, as they can do great things regardless of their nanoscale size. The power of the mass is the key.

“Instead of using single switches, we put millions or billions of them together. Together they cooperate and intensify the desired property. When a nanoscale phenomenon is intensified this way, all kinds of mechanical macro-scale movements may result – microrobots of sorts.”

Deploying light-controlled microrobots

According to Priimägi, it is possible to attain forces of similar scope in the studied materials with light as generated by a human muscle when contracted.

“Light-based movements have been used for moving small particles from one place to another, for example. The particles moved have been dozens of times heavier than the microrobot causing the movement. This type of robotics could perhaps be used for super-precise light-controlled placement and disposition of small items, for example,” Priimägi envisions.

“In wilder visions, a tiny light-controlled microrobot could move from one place to another on a surface in a controlled manner and transmit information or move materials between different parts of a microcircuit.”

Applications from interdisciplinary collaboration

Laser

 

The research of light-based technologies goes hand in hand with materials development, and TUT has strong merits in both.

 

Since these developments concern fundamental research and they are still largely based on hypotheses, it is impossible to list practical applications at this point.

“Our actual goal is a kind of a future technology platform, or a material concept that could be used for many types of purposes across disciplinary borders. This is why interdisciplinary cooperation within TUT and both nationally and internationally is needed to find applications,” Priimägi says.

The research of light-based technologies goes hand in hand with materials development, and TUT has strong merits in both. In addition, there is great bioengineering expertise at TUT.

Enhanced sensor sensitivity and organic electronics

Light-controlled materials could possibly be used in the field of bioengineering, for example, to improve the detection of various molecules, viruses and bacteria in test samples. In principle, the technique Priimägi studies can be applied to any chemical.

“As regards organic electronics, we intend to study if quantities such as conductivity or capacitance can be controlled with light. If we succeed, this could be a link to more advanced applications.”

Different materials interact in different ways with light, and different molecules can be detected more effectively with different colour light sources. A small laser with an adjustable colour could be useful in sensor applications, and developing one is, in fact, included in the goals of the project.

Light control also enables controlling the friction properties and wettability of a surface and producing externally-controlled self-cleaned surfaces.

“In industrial measurements, light-based technologies can be controlled remotely. Therefore, they can be applied in places where electric control cannot be used.”

Kinetic energy from sunlight?

Photonics employs widely around Europe

  • Photonics employs approx. 290,000 people directly and 30 million people indirectly around Europe.
  • The annual worldwide turnover of light-based technologies is 300 billion euros.
  • The share of Europe in the worldwide turnover is 20 per cent, i.e. approx. 60 billion euros. In certain sectors, such as lighting, Europe makes up 40 per cent.
  • The annual growth forecast for light-based technologies is 8 per cent.

(Source: Toward 2020 – Photonics Driving Economic Growth in Europe, Multiannual Strategic Roadmap 2014 – 2020, A report published by the European Technology Platform Photonics 21 in spring 2013)

 

The most tremendous visions speculate on the harnessing of sunlight and turning it into kinetic energy to be utilized in various technological applications in the energy branch.

“This is definitely worth looking into, and the idea is indeed being studied elsewhere. But we have a long way to go before we can actually harness sunlight-driven movement for something useful in the materials we study. I believe that the first potential applications will be rather found on the micro-scale and that the light control will be implemented with lasers or LEDs,” Priimägi notes.

“We must combine chemistry and physics in order to learn how to both manufacture these materials and transform them in a way that allows us to harness light energy for generating movement. For the most part, we can study these materials with the existing equipment.”

The research topic picked me

Arri Priimägi’s career with light-controlled materials began a decade ago. He already studied similar materials in his master’s thesis, but from a whole different perspective. The vast potential of the field keep the scientist intrigued.

“I would not say that I sought this area of research. It was the topic that picked me,” Priimägi says.

“The further you dive into a research topic, the more widely it reveals itself. But at the core of it all are the tiny little molecule switches – they have companied with me throughout the journey. They are truly fascinating.”

Text: Leena Koskenlaakso
Photos: Mika Kanerva

 
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