DURHAM, N.C. Scientists drew fittingly from Roman mythology when they named a unique class of miniscule particles after the god Janus, who is usually depicted as having two faces looking in opposite directions.
For years, scientists have been fascinated by the tantalizing possibilities of these particles for their potential applications in electronic display devices, sensors and many other devices. However, realizing these applications requires precise control over the positions and orientation of the particles, something which has until now eluded scientists.
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. Their unique technology should make it more likely that Janus particles can be used as the building blocks for a myriad of applications, including such new technologies as electronic paper and self-propelling micromachines.
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.
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
|Contact: Richard Merritt|