A Casimir chip that exploits the vacuum energy
July 31, 2012
Casimir forces on parallel plates (credit: Wikipedia Commons)
University of Florida researchers have have developed a way to keep objects flat enough
to measure the strange Casimir force, which pushes two parallel conducting plates together
when they are just a few dozen nanometers apart, Technology Review Physics arXiv Blog
reports.
They carved a single device out of silicon that is capable of measuring the Casimir force
between a pair of parallel silicon beams, the first on-chip device capable of doing this.
The device consists of one fixed beam and another moveable one attached to an
electromechanical actuator. Other shapes should be possible to manufacture too. “This
scheme opens the possibility of tailoring the Casimir force using lithographically defined
components of non-conventional shapes,” the researchers say.
So instead of being hindered by uncontrollable Casimir forces, the next generation of
microelectromechanical devices should be able to exploit them, perhaps to make
stictionless bearings, springs and even actuators.
[+]
The set-up of the experiment and device. (a) A simplified schematic (not to scale) of the
beam, movable electrode and comb actuator supported by four springs, with electrical
connections. The current amplifier provides a virtual ground to the right end of the beam.
The suspended and anchored parts of the comb actuator are shown in dark and light colors
respectively. The separation d between the beam and the movable electrode was
controllably reduced so that the Casimir force can be detected. (b)-(e) Scanning electron
micrographs of the entire micromechanical structure (b) and close-ups of: the doubly
clamped beam (c), zoomed into the white dashed box in (b); the comb actuator (d) and the
serpentine spring (e). (Credit: J. Zou, et al.)
[+]
Verios (credit: FEI)
Microscopes for viewing nanoscale devices
Monitoring these kind of ultra-small nanoscale devices requires special microscopes, such
as the scanning electron microscope (SEM), which images a sample by scanning it with a
beam of electrons. (The Casimir device image above is an example of an SEM image).
An SEM can produce very high-resolution images of a sample surface, revealing details
less than 1 nanometer in size (the size of small biomolecules).
FEI has just announced the new Verios XHR SEM, which provides the sub-nanometer
resolution and enhanced contrast needed for precise measurements in materials science
and advanced semiconductor manufacturing applications.
An even higher-resolution microscope is the transmission electron microscope (TEM), with
a resolution of 0.5 Angstroms (.05 nm). An example of a TEM image is shown in this news
item today on graphene layers.
Another type of nanoscale microscope is the atomic force microscope (AFM). It has several
advantages over the 2D SEM; it provides a 3D surface profile, for example. It also has
disadvantages: it doesn’t allow for large scanned images, and is very slow, for example.
Nonetheless, AFMs are vital tools in nanotechology, and nanoHUB.org has just announced
a two-part, web-based course covering the principles and practice of atomic force
microscopy.