A nanorod is
switched between two states – bright (high signal) and dark (low signal) by an
external
electrical pulse (red trace). The state of the rod can be readout
instantaneously
at any time using
polarized light. The rod stores the most recently written state until the
arrival of the
next «write pulse». (Image: UZH)
(August 18, 2015) For
the first time ever, researchers have succeeded in creating arrangements of
colloids – tiny particles suspended in a solution – and, importantly, they have
managed to control their motion with high precision and speed. Thanks to this
new technique developed by scientists at the University of Zurich, colloidal
nanoparticles may play a role in digital technologies of the future.
Nanoparticles can be rapidly displaced, require little energy and their small
footprint offers large storage capacity – all these attributes make them well
suited to new data storage applications or high-resolution displays.
Colloids are minute particles that are finely distributed
throughout a liquid. Suspensions of colloidal particles are most familiar to us
as beverages, cosmetics and paints. At a diameter in the range of ten to one
hundred nanometres, a single such particle is invisible to the naked eye. These
nanoparticles are constantly in motion due to the principle of Brownian motion.
Since the particles are electrically charged, they experience forces of
attraction and repulsion that can be harnessed to control and manipulate their
behavior. In experiments carried out five years ago, Madhavi Krishnan,
Professor of Physical Chemistry at the University of Zurich, succeeded in the
controlled spatial manipulation of matter on the nanometer scale. In a new
study, she and her colleagues have now demonstrated that it is not only
possible to spatially confine nanoparticles, but also to control their position
and orientation in time and to do so in a liquid, without using physical
contact.