Possibilities are endless for new material that moves itself towards light

24 Jul 2018

A film deflects from a magnetic field when exposed to light. Image: SilkLab/Tufts University

Solar arrays that autonomously bend towards a light source could be possible thanks to a major materials science breakthrough.

A few weeks ago at Inspirefest 2018, we heard about the challenges that exist for solar energy panels when the main source of energy moves out of sight with the rotation of the Earth.

But what if it were possible for these solar panels to move over the course of a day without any human interaction?

That is now a possibility following the creation of a range of new materials that can move in a variety of different ways when exposed to light.

In a paper published to the Proceedings of the National Academy of Sciences, the research team from Tufts University in the US revealed its magnetic elastomeric composites inspired by nature itself.

Just as flowers and leaves are capable of turning towards sunlight, these new materials can change their magnetic properties after a particular temperature is reached, otherwise known as Curie temperature.

So, by heating or cooling a magnetic material, it is possible to turn magnetism on and off. In this instance, biopolymers and elastomers doped with ferromagnetic CrO2 will heat up when exposed to lasers or sunlight.

This results in its magnetic properties being lost until it cools down again, and the basic movements of the material – shaped into sponges, films and hydrogels – are induced by nearby permanent or electromagnets, causing bending, twisting and expansion.

“We could combine these simple movements into more complex motion, like crawling, walking or swimming,” said Fiorenzo Omenetto, corresponding author of the study.

“And these movements can be triggered and controlled wirelessly, using light.”

First of its kind

A demonstration of the technology showed how a soft gripper device could capture and release objects in response to light.

Meng Li, first author of the paper, said that specific portions of a device could be activated for various uses.

“And, unlike other light-actuated materials based on liquid crystals, these materials can be fashioned to move either toward or away from the direction of the light,” she said.

“All of these features add up to the ability to make objects large and small with complex, coordinated movements.”

The materials used to create the new processes included polydimethylsiloxane, a widely used transparent elastomer often shaped into flexible films and capable of being shaped into a wide range of forms.

Omenetto added: “We could theoretically achieve even more complicated and fine-tuned movements, such as folding and unfolding, microfluidic valve-switching, micro- and nano-sized engines, and more.”

Colm Gorey was a senior journalist with Silicon Republic