Casimir effect put to work as a nano-switch
11:06 02 July 2010 by Eugenie Samuel Reich
For similar stories, visit the Nanotechnology Topic Guide
A new technique that takes control of the Casimir effect – a strange quantum phenomenon that gums up nanoelectromechanical systems (NEMS) – may pave the way to a switch that could cut the power consumption of nanoscale gadgets.
The Casimir effect tends to force together two parallel conducting plates when they are a few micrometres apart or less. It arises because of the quantum electromagnetic fluctuations that always occur in a vacuum. The close proximity of the two plates constrains the fluctuations in the gap between them. This makes the fluctuation between the plates weaker than those in the surrounding space, so the plates are pushed together.
The effect was named after Dutch physicist Hendrik Casimir, who predicted its existence in 1948. Nanotechnologists are keen to tame it, because it gums up their nanoscopic machines.
A European research team has now done just that, using a material already used in rewritable CDs and Blu-ray discs. AIST, an alloy of silver, indium, antimony and tellurium, reversibly switches from a crystalline to an amorphous state when heated by a laser, allowing data to be written and rewritten onto a disc.
Golden ball
The team deposited AIST on an aluminium-coated silicon wafer and held it between 40 and 120 nanometres from a gold sphere in an ultra-high vacuum. When AIST was in an amorphous form, the Casimir force measured about 100 piconewtons, but it increased by 20 to 25 per cent when the AIST was in its crystalline form.
This is because the crystalline phase is more reflective, so it confines the electromagnetic fluctuations more effectively and so increases the Casimir force.
Group member George Palasantzas at the University of Groningen in the Netherlands says this phenomenon could be used to build a new type
of low-power nanoswitch. The switch would be physically moved by altering the state of the AIST, and so changing the strength of the Casimir force.
“The state remains stable even when power is turned off, which is a unique feature,” Palasantzas says – unlike existing nanoswitches, such as those used to switch the transmission frequency in mobile phones.
Davide Iannuzzi of the Free University in Amsterdam, the Netherlands, who was not involved in the study, says it is “an important contribution”, though he warns that in real applications, the build-up of electric charge between moving parts may have more of an effect on the nanoswitch than the Casimir force. “If one finds an easy way to control the [electric charge], then the Casimir force becomes indeed interesting – but that is quite a challenge,” he says.
Palasantzas, however, predicts that ways will be found to minimise the electrostatic build-up, so that the Casimir force exceeds the electrostatic force for distances below about 100 nanometres.
(No Ratings Yet)