Researchers measure repulsive Casimir forces



Surgery to treat obesity could be avoided if GPs and healthcare trusts put more time and money into early stage weight management programmes, a senior clinical researcher will say today (Wednesday, 17 December, 2008). And he will say that patients suffering from obesity face a “post code lottery” when seeking access to specialist care. Speaking

Full Post: GPs ‘could do more’ to help obese avoid surgery

Researchers from Harvard University and the National Institutes of Health (NIH) have measured, for the first time, a repulsive quantum mechanical force that could be harnessed and tailored for a wide range of new nanotechnology applications.

The study, led by Federico Capasso, Robert L. Wallace Professor of Applied Physics at Harvard’s School of Engineering and Applied Science (SEAS), will be published as the January 8 cover story of Nature .

The discovery builds on previous work related to what is called the Casimir force. While long considered only of theoretical interest, physicists discovered that this attractive force, caused by quantum fluctuations of the energy associated with Heisenberg’s uncertainty principle, becomes significant when the space between two metallic surfaces, such as two mirrors facing one another, measures less than about 100 nanometers.

“When two surfaces of the same material, such as gold, are separated by vacuum, air, or a fluid, the resulting force is always attractive,” explained Capasso.

Remarkably, but in keeping with quantum theory, when the scientists replaced one of the two metallic surfaces immersed in a fluid with one made of silica, the force between them switched from attractive to repulsive. As a result, for the first time, Capasso and his colleagues measured what they have deemed a repulsive Casimir.

To measure the repulsive force, the team immersed a gold coated microsphere attached to a mechanical cantilever in a liquid (bromobenzene) and measured its deflection as the distance from a nearby silica plate was varied.

“Repulsive Casimir forces are of great interest since they can be used in new ultra-sensitive force and torque sensors to levitate an object immersed in a fluid at nanometric distances above a surface. Further, these objects are free to rotate or translate relative to each other with minimal static friction because their surfaces never come into direct contact,” said Capasso.

By contrast, attractive Casimir forces can limit the ultimate miniaturization of small-scale devices known as Micro Electromechanical Systems (MEMS), a technology widely used to trigger the release of airbags in cars, as the attractive forces may push together moving parts and render them inoperable, an effect known as stiction.

Potential applications of the team’s finding include the development of nanoscale-bearings based on quantum levitation suitable for situations when ultra-low static friction among micro- or nano-fabricated mechanical parts is necessary. Specifically, the researchers envision new types of nanoscale compasses, accelerometers, and gyroscopes.

http://www.harvard.edu/

Link




Magicians have long created the illusion of levitating objects in the air. Now researchers at the National Institutes of Health and Harvard University have actually levitated an object, suspending it without the need for external support. Working at the molecular level, the researchers relied on the tendency of certain combinations of molecules to repel each

Full Post: Levitating nanomechanics shows potential to improve medicine



Cells are filled with membrane-bound organelles like the nucleus, mitochondria and endoplasmic reticula. Over the years, scientists have made much progress in understanding the biomolecular details of how these organelles function within cells, but understanding the actual physical forces that maintain the structures of these organelles’ membranes continues to be a challenge. Now, UCLA Henry

Full Post: Mathematical model shows how organelles function within cells



Determining the mechanisms that shape biological membranes has long been a tricky business. Like a factory assembly line, eukaryotic cells are organized into membrane-bound, functional compartments called organelles. For instance, the nucleus is the repository of genetic information and houses the machinery that creates the messenger RNA transcripts, which direct the synthesis of new protein.

Full Post: Doing the math for membranes



Clarkson University Center for Advanced Materials Processing Professor Igor Sokolov and graduate student Ravi M. Gaikwad have discovered a new method of protecting teeth from cavities by ultrafine polishing with silica nanoparticles. The researchers adopted polishing technology used in the semiconductor industry (chemical mechanical planarization) to polish the surface of human teeth down to nanoscale

Full Post: Ultrafine polishing with silica nanoparticles protects teeth



Using tiny gold particles and infrared light, MIT researchers have developed a drug-delivery system that allows multiple drugs to be released in a controlled fashion. Such a system could one day be used to provide more control when battling diseases commonly treated with more than one drug, according to the researchers. “With a lot of

Full Post: Gold particles and infrared light for controlled drug delivery