Making light work of artificial muscles

Jan 21, 2011
The light-responsive film is made up of polymer brushes (right) that have self-assembled into a two-layer, three-dimensional array (left). Credit: Reproduced, with permission, from Ref. 1 2011 American Association for the Advancement of Science

A new form of self-assembling polymer film that bends and stretches when hit by light is pointing the way to a new family of functional materials. This flexing film is the first material to have been made by coaxing complex molecules to form large-scale, highly ordered three dimensional arrays -- a discovery that could change the way that many active material are made, from artificial muscles to solar cells.

Nobuhiko Hosono, Takuzo Aida and colleagues at RIKEN Advanced Science Institute in Wako and The University of Tokyo developed the self-assembly protocol. The researchers found that brush-shaped polymers would form an orderly film when hot-pressed between two sheets of Teflon.

They made their discovery while studying a in which each side chain, or bristle, of the brush structure incorporates light-responsive azobenzenes—two benzene rings separated by a pair of nitrogen atoms. When hit by UV light, the bond between the nitrogens rearranges, contracting the side chain.

The researchers used this photoisomerization behavior to confirm the remarkable long-range order of the polymer structure. Because the side chains were all aligned, when those at the surface were hit by light they curled up in concert, bending the film. A second beam of light at a different wavelength reversed the isomerization process, and the film relaxed back to its original shape.

The trick to making the material is to heat it between two sheets of Teflon that have been drawn tight in one direction, says Hosono. This tension orients the Teflon sheets’ internal structure along a single axis, which acts as a template for the molten polymer brushes sandwiched in between. The side chains of the polymer brush align with the Teflon, pulling each brush upright. As each polymer brush aligns in the same way, it forms a repeating three-dimensional array.

Hosono, Aida and colleagues expect the technique to work for other polymer brushes with similar side chains. To improve the artificial muscle-like behavior of their , Hosono says the team will try cross-linking the polymer . This will prevent the molecular structure from becoming disordered as the polymer repeatedly curls and relaxes over many cycles, giving the muscle a longer lifetime.

The team is already assessing other potential applications. The wide-area three-dimensional molecular ordering of the polymer brush has great potential for building electronic devices, says Hosono. “We now have designed a new type of polymer brush for development of highly efficient thin-layer organic .”

Explore further: Shapeshifting plastics could revolutionize microrobotics and minimally invasive surgery

More information: Hosono, N., et al. Large-area three-dimensional molecular ordering of a polymer brush by one-step processing. Science 330, 808-811 (2010).
Read the article here: www.sciencemag.org/content/330/6005/808.short

add to favorites email to friend print save as pdf

Related Stories

Undercover Tactics

May 10, 2005

Soft shell, hard core: nanotubes made of cyclic peptides with a synthetic polymer coating Ever since the discovery of carbon nanotubes in the early 1990s, scientists and engineers have been fascinated by the possibilities ...

Polymer synthesis could aid future electronics

Jul 19, 2010

(PhysOrg.com) -- Tomorrow's television and computer screens could be brighter, clearer and more energy-efficient as a result of a process developed by a team of researchers from Canada and the Department of ...

Recommended for you

Chemists eye improved thin films with metal substitution

15 hours ago

The yield so far is small, but chemists at the University of Oregon have developed a low-energy, solution-based mineral substitution process to make a precursor to transparent thin films that could find use ...

Essential oils may provide good source of food preservation

19 hours ago

A new study in the Journal of Food Science, published by the Institute of Food Technologists (IFT), found that essential oils may be able to be used as food preservatives in packaging to help extend the shelf-life of foo ...

Researchers create safe, resistant material to store waste

21 hours ago

(Phys.org) —Storing industrial waste has never been a pretty job, and it's getting harder. New techniques for refining such metals as aluminum and vanadium, for example, also yield new byproducts that have ...

User comments : 0