One of the big research tracks for nanotechnology is the ability to control the alignment and shape of nanoparticles. Control is vital for nano-manufacturing (building something with nanoparticles) and also for many medical uses of nanotechnology. “Control” in this sense means the ability to move nanoparticles on command in any dimension with the ultimate control being “six degrees of freedom” (forward/backward, up/down, left/right, plus rotation with pitch, yaw, and roll). This is not hard to visualize with, say, something the size of a baseball; but fiendishly complex when it involves billions of particles about one-millionth the size of this dot (.). One such particle, known by its two-surface shape is the Janus particle (named for the two faced Roman god). New research with the Janus particle may lead to important applications:

Typical Janus particles consist of miniscule spherical beads that have one hemisphere coated with a magnetic or metallic material. External magnetic or electric fields can then be used to control the orientation of the particles. However, this coating interferes with optical beams, or traps, another tool scientists use to control positioning. Duke University engineers say they can for the first time control all the degrees of the particle’s motion, opening up broad possibilities for nanotechnology and device applications.

The breakthrough of Duke engineers was to devise a fabrication strategy to coat the particle with a much smaller fraction of material. This discovery allows these particles to be compatible with optical traps and external magnetic fields, allowing for total control over the particles’ positions and orientations. “Past experiments have only been able to achieve four degrees of control using a combination of magnetic and optical techniques,” said Nathan Jenness, a graduate student who completed his studies this year from Duke’s Pratt School of Engineering. He and co-author Randall Erb, also a graduate student, were first authors of a paper appearing online in the journal Advanced Materials. “We have created a novel Janus particle that can be manipulated or constrained with six degrees of freedom.” The researchers have dubbed the unique particles they created “dot-Janus” particles.

“Being able to more completely control these particles affords us a greater ability to measure the mechanical properties of biomolecules, including DNA,” Yellen said. “It may also be possible to control the behavior of cells by manipulating dot-Janus particles attached to cell surfaces. These biological applications, as well as the ability to control the assembly of nanostructures, establish the broad scientific value of these findings.”

[Source: Nanotechnology Today]