IISc researchers have successfully found a way to navigate tiny, geometrically identical filaments, and subsequently place them at predefined positions with respect to each other. The method works without any physical contact with the filaments, and this can have important applications in nanomedicine.
The filaments used are extremely small screw-like nanostructures which can’t be seen by bare eyes. In fact, they are so small that a few of them can sit comfortably on the tip of a human hair.
Maneuvering nanostructures is crucial for realising the dream of nanomedicine. Nanomedicine can develop ways to carry packets of drugs to the site of sick cells, and deliver the drugs in a controlled manner. Though there is considerable progress on the delivery mechanism, controlling the movement of packets in biological liquids like blood has remained a challenge.
Scientists have long used instruments called ‘optical tweezers’ to maneuver small structures in fluidic environments. Though they are good at controlling the motion, they require intense laser beams, proximity to a focusing lens, and hence are not the right choice for operations in living systems. Also, they don’t work with metals.
The researchers studied how two geometrically similar nanostructures could be moved and positioned under the influence of magnetic fields. They used a combination of two types magnetic fields: one constant, and the other constantly varying with time. The constant field aligned the nanostructures along different directions, and the oscillating field gave them the energy to move. The combined effect of these moved the nanostructures in two separate directions, and researchers could control the motion by tweaking the magnetic field. The only required condition is that the filaments should be close to a solid surface.
“We have developed a completely non-invasive method to independently maneuver nanoscale objects in a fluid, which are geometrically identical”, says Dr Ambarish Ghosh, who led the study.
Like many novel ideas, the idea of manipulating motion using magnetic fields is inspired by nature. A type of bacteria, called the magnetotactic bacteria, align themselves in the direction of the Earth’s magnetic field, and use their internal energy to move.
Ambarish Ghosh and his team also followed the experiment with computer simulation study for extending the method any number of particles. “Although the demonstration was for two particles, we have showed that the method can be extended to many”, says Ambarish Ghosh.
The researchers believe that their method of controlling the nanostructures could be handy in “microfluidic applications that require precise assembly of individual components”.
About the authors:
Dr Ambarish Ghosh is an Assistant Professor at the Centre for Nano Science and Engineering (CeNSE), Indian Institute of Science, Bangalore. He is also associated with the Department of Electrical Communication Engineering and the Department of Physics. Pranay Mandal is a PhD student at CeNSE, and Vaishali Chopra is a Project Assistant in CeNSE.
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About the paper:
The paper appeared in the journal ACS Nano. It can be accssed at pubs.acs.org/doi/abs/10.1021/acsnano.5b01518