It took experts three years to believe their results

Mar 18, 2010 11:56 GMT  ·  By
After 72 hours of exposure to ambient light, strands of nanoparticles twisted and bunched together
   After 72 hours of exposure to ambient light, strands of nanoparticles twisted and bunched together

Any first-grader will tell you that matter can bend and twist light. This is obvious in anything from mirrors to space telescopes, and from lasers to polarizing 3D glasses. But the opposite interaction has almost never been observed, in the sense that experts rarely saw light influence matter in the same way. Now, in a findings that took University of Michigan researchers three years to believe, it has been revealed that photons – the basic particles in light – can influence matter as well. The targets of the investigation were ribbons of neatly-ordered nanoparticles. Details of the research appear in the latest issue of the top publication Science.

The team was led by principal investigator Nicholas Kotov, who is a professor in the departments of Chemical Engineering, Biomedical Engineering and Materials Science and Engineering at the university. “I didn't believe it at the beginning. To be honest, it took us three and a half years to really figure out how photons of light can lead to such a remarkable change in rigid structures a thousand times bigger than molecules,” the expert says of his team's findings. In previous researches, it has been demonstrated that molecular-scale matter could indeed be influenced by light.

However, the same interactions were never observed in the case of larger particles, such as the ones in the new study. The research team highlights the fact that their nanostructures were between one and four micrometers long, which means that they contained numerous molecules. “We discovered that if we make flat ribbons in the dark and then illuminate them, we see a gradual twisting, twisting that increases as we shine more light. This is very unusual in many ways,” Kotov says. For the experiments, the team used cadmium telluride structures suspended in a water-based solution.

Producing spiraled nanostructures is something new to nanotechnology. UM postdoctoral researcher Sudhanshu Srivastava is, for example, working in his lab trying to make these spiraled ribbons move. “He's making very small propellers to move through fluid – nanoscale submarines, if you will. You often see this motif of twisted structures in mobility organs of bacteria and cells,” Kotov reveals. Possible applications for the new technology that spring to mind immediately include the development of advanced microfluidic devices, as well as to the creation of microelectromechanical systems (MEMS) that are controlled by light. Particles created in this manner could be successfully used for delivering drugs as well.