By manipulating the magnetization of a liquid solution, the researchers have for the first time coaxed magnetic and non-magnetic materials to form intricate nano-structures. The resulting structures can be “fixed,” meaning they can be permanently linked together. This raises the possibility of using these structures as basic building blocks for such diverse applications as advanced optics, cloaking devices, data storage and bioengineering.
Changing the levels of magnetization of the fluid controls how the particles are attracted to or repelled by each other. By appropriately tuning these interactions, the magnetic and non-magnetic particles form around each other much like a snowflake forms around a microscopic dust particle.
“We have demonstrated that subtle changes in the magnetization of a fluid can create an environment where a mixture of different particles will self-assemble into complex superstructures,” said Randall Erb, fourth-year graduate student. He performed these experiments in conjunction with another graduate student Hui Son, in the laboratory of Benjamin Yellen, assistant professor of mechanical engineering and materials science and lead member of the research team.
And it’s a unique collaboration between chemists and neuroscientists that led to the discovery of a remarkable new way to use light to activate brain circuits with nanoparticles.
Ben Strowbridge, an associate professor in the neurosciences department in the Case Western Reserve School of Medicine and Clemens Burda, an associate professor in chemistry, say it’s rare in science that people from very different fields get together and do something that is both useful and that no one had thought of before. But that is exactly what they’ve done.
By using semiconductor nanoparticles as tiny solar cells, the scientists can excite neurons in single cells or groups of cells with infrared light. This eliminates the need for the complex wiring by embedding the light-activated nanoparticles directly into the tissue. This method allows for a more controlled reaction and closely replicates the sophisticated focal patterns created by natural stimuli.
The electrodes used in previous nerve stimulations don’t accurately recreate spatial patterns created by the stimuli and also have potential damaging side effects.
“There are many different things you’d want to stimulate neurons for-injury, severed or damaged nerve to restore function- and right now you have to put a wire in there, and then connect that to some control system. It is both very invasive and a difficult thing to do,” says Strowbridge.
IIn principle, the researchers should be able to implant these nanoparticles next to the nerve, eliminating the requirement for wired connections. They can then use light to activate the particles.