Alternative Energy

How we see things around us without noticing it! We know the peculiar habit of the sunflower. How it moves with the movement of the sun everyday. But if we want to move anything with the help of sunlight we are not as lucky as the sunflower is. We first have to convert sunlight into heat or electricity and then convert any of this into mechanical energy. Scientists are trying to imitate the action of the sunflower at nanoscale right now. It is no less than a miracle but scientists are the greatest magicians on this earth. Coming generations will reap the benefits of their hard work. A team of the University of Florida chemists is trying a new mechanism to transform light straight into motion – albeit at a very, very, very tiny scale.

Their paper will appear soon in the online edition of the journal Nano Letters. The UF team developed a new type of “molecular nanomotor” driven only by photons. Photons are also known as particles of light. While this is not the first photon-driven nanomotor, but what differentiates this nanomotor with others is that this almost microscopic device is entirely made up of a single molecule of DNA. This feature makes this photon nanometer special because this simplicity enhances the flexibility of the device. When we are going to use this photon nanomotor in the real world we can easily upgrade, modify, alter the existing one for development, manufacture and real-world applications. It is said that this technology can be used for various purposes and it ranges from medicine to manufacturing.

Huaizhi Kang, who is the doctoral student in chemistry at UF and the first author of the paper said, “It is easy to assemble, has fewer parts and theoretically should be more efficient.”

We have to stress the point again and again that the scale of the nanomotor is almost vanishingly small but its implications are not.

In its clasped, or closed, form, the nanomotor measures 2 to 5 billionths of a meter. When it is unclasped, it extends as long as 10 to 12 nanometers. According to the apparent scientific calculations the nanomotor uses considerably more of the energy in light than traditional solar cells, the amount of force it exerts is proportional to its small size. But it should be clear that size is not going to be a limiting factor.

If we try to peek into the future the nanomotor will successfully be applied to microscopic devices. It can repair a defunct cell or fight viruses or bacteria. Nanomotor is made up of DNA, so it is biocompatible. Although in the conceptual stage, those devices, like much larger ones, will require a power source to function. One more advantage of the nanomotor is it leaves no waste when it converts light energy into motion.

“Preparation of DNA molecules is relatively easy and reproducible, and the material is very safe,” said Yan Chen, a UF chemistry doctoral student and one of the authors of the paper.

But the practical world applications don’t seem easy. If we want to run an assembly line production or drive a vehicle by using nanomotors we would need trillions of those. They have to work together in harmony. Weihong Tan, a UF professor of chemistry and physiology, author of the paper and the leader of the research group reporting the findings, acknowledged, “The major difficulty lies ahead that is how to collect the molecular level force into a coherent accumulated force that can do real work when the motor absorbs sunlight.”

Tan is quite optimistic that the group has already begun working on the problem and they would find a solution. He said, “Some prototype DNA nanostructures incorporating single photo-switchable motors are in the making which will synchronize molecular motions to accumulate forces.”

How idi the team create the nanomotor? The research team combined a laboratory-created DNA molecule with azobenzene. Azobenzene is a chemical compounds that reacts to light. A high-energy photon prompts one response, lower energy, another. The researchers attached a fluorophore, or light-emitter, to one end of the nanomotor to demonstrate the movement. At another end they had a quencher, which can quench the emitting light. Their instruments recorded emitted light intensity that corresponded to the motor movement. The research is being funded by the National Institutes of Health and the National Science Foundation.

“Radiation does cause things to move from the spinning of radiometer wheels to the turning of sunflowers and other plants toward the sun,” said Richard Zare, distinguished professor and chairman of chemistry at Stanford University. “What Professor Tan and co-workers have done is to create a clever light-actuated nanomotor involving a single DNA molecule. I believe it is the first of its type.”