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Topic: Superlubricity

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	What is Superlubricity?
		This superlubricity phenomenon occurs when two surfaces have crystal lattices which are in incommensurate contact, meaning that the crystal arrangement is such that only a tiny minority of the atoms on the surface come in contact with the opposing surface, generating a vanishingly small amount of friction.
		Superlubricity was discovered when physicists studied, at very high precision, the friction force between crystal surfaces.
		Superlubricity and its study is a relatively recent field, brought up in 1991 but not studied much in the meanwhile.
	www.wisegeek.com /what-is-superlubricity.htm (335 words)

	Superlubricity - Wikipedia, the free encyclopedia
		Superlubricity is a certain phenomenon in which friction can vanish almost completely.
		It is an effect that has been already suggested in 1991 but has recently been measured with great accuracy between two graphite surfaces.
		One should note that the similarity of the term superlubricity with terms such as superconductivity and superfluidity is misleading; other energy dissipation mechanisms can lead to a finite (normally small) friction force.
	en.wikipedia.org /wiki/Superlubricity (195 words)

	Superlubricity (Site not responding. Last check: 2007-11-02)
		Superlubricity is an effect that has been already suggested in 1991 but has recently been measured with great accuracy between two graphite surfaces.
		It describes the effect that friction can vanish almost completely even when two crystalline surfaces slide over each other in dry contact when there are in incommensurate contact.
		Note: The similarity of the term superlubricity with terms such as superconductivity and superfluidity is misleading since other energy dissipation mechanisms can lead to a finite (normally small) friction force.
	www.bidprobe.com /en/wikipedia/s/su/superlubricity.html (177 words)

	Graphite - Wikipedia, the free encyclopedia
		Other characteristics: thin flakes are flexible but inelastic, mineral can leave fl marks on hands and paper, conducts electricity, and displays superlubricity.
		Recent studies suggest that an effect called superlubricity can also account for this effect.
		The use of graphite is also limited by its tendency to facilitate pitting corrosion in some stainless steels, and to promote galvanic corrosion between dissimiilar metals.
	en.wikipedia.org /wiki/Black_lead (832 words)

	Superlubricity Information
		Superlubricity is a certain phenomenon in which friction can vanish almost completely.
		Superlubricity occurs when two crystalline surfaces slide over each other in dry, incommensurate contact.
		One should note that the similarity of the term superlubricity with terms such as superconductivity and superfluidity is; misleading; other energy dissipation mechanisms can lead to a finite (normally small) friction force.
	superlubricity.zdnet.co.za /zdnet/Superlubricity (371 words)

	Superlubricity (Site not responding. Last check: 2007-11-02)
		Superlubricity is a certain phenomenon in which Friction can vanish almost completely.
		Superlubricity occurs when two crystalline surfaces slide over each other in dry, incommensurate contact.
		One should note that the similarity of the term superlubricity with terms such as Superconductivity and superfluidity is misleading; other energy dissipation mechanisms can lead to a finite (normally small) friction force.
	www.ufaqs.com /wiki/en/su/Superlubricity.htm (172 words)

	Reducing friction at the atomic scale » Francis Sedgemore
		Exploiting an effect known as superlubricity, a group of researchers led by Anisoara Socoliuc and Enrico Gnecco from Basel University have found a way of reducing friction between sliding nano-contacts to negligible values.
		Superlubricity, which can be found in many natural phenomena from biological systems to tectonic plates, occurs when two crystalline surfaces slide over each other in dry contact.
		The researchers found that by applying an AC voltage to the tip of an atomic force microscope moving over a surface, and tuning the current to a mechanical resonance frequency of the system, the tip and surface slide past each other without jumping from atom to atom in ‘stick-slip’ fashion and dissipating energy.
	www.skysong.eu /2007/01/reducing-friction-at-the-atomic-scale (417 words)

	Superlubricity: a state of vanishing friction
		The state of vanishing friction called superlubricity are discussed from theoretical and experimental viewpoints.
		In this experiment, Si(001) (n-type, 0.01 Ømega \cdot cm) is one-dimensionally scanned against a W tip in ultra-high vacuum, and the W tip-deflection caused by the friction appearing between the scanned Si(001) and the W(011) on the polycrystalline W tip is measured.
		It is thus concluded that the observed frictional anisotropies stemming from the differences in the commensurability of the contacting surfaces imply the existence of superlubricity.
	flux.aps.org /meetings/BAPSMAR95/abs/SF3006.html (249 words)

	Superlubricity - Elsevier (Site not responding. Last check: 2007-11-02)
		Superlubricity is defined as a sliding regime in which friction or resistance to sliding vanishes.
		Superlubricity reviews the latest methods and materials in this area of research that are aimed at removing friction in nano-to-micro scale machines and large scale engineering components.
		Insight is also given into the atomic-scale origins of friction in general and superlubricity while other chapters focus on experimental and practical aspects or impacts of superlubricity that will be very useful for broader industrial community.
	www.elsevier.com /wps/find/bookaudience.cws_home/711047/description (593 words)

	MM breakthroughs needed - WiseNano
		It looks like kinematic ("robotic") machines will need some design tweaks vs. large-scale machines, but can be approached with mechanical engineering discipline--just different parameters.
		A few techniques like "frictionless" surfaces (using superlubricity) still have to be worked out.
		Once mechanics work, nanoscale power, control, sensing, and computation will be straightforward.
	wise-nano.org /w/MM_breakthroughs_needed (537 words)

	nanotribo.org
		This length scale is independent of the dimensions of the contact, leading to the prediction of a peculiar effect called "superlubricity".
		Namely, if the lattice spacing or the mutual orientation of the lattices in contact are not identical, the local frictional forces should exhibit a two-dimensional periodicity, with a high degree of mutual cancellation.
		W against W), in order to obtain maximum 'contrast' between friction and superlubricity, or a different material (e.g.
	www.nanotribo.org /projects/project_10 (810 words)

	da Grafit Graphite is one of the allotropes allotropes of...
		The loose coupling among the sheets in graphite contributes to another industrially important property -- graphite powder is used as a dry lubricant lubricant.
		Recent studies suggest that an effect called superlubricity superlubricity can also account for this effect.
		In graphite the effect superlubricity superlubricity also takes place Notable occurrences include New York and Texas, USA; Russia; Mexico; Greenland and India.
	www.biodatabase.de /Graphite (367 words)

	[No title] (Site not responding. Last check: 2007-11-02)
		Jin, The purpose of this e-mail is to invite you to participate in a Special Symposium titled "Superlubricity: Myth or Reality!" As you know, in recent years, there has been an overwhelming interest in fundamental and experimental studies that relate to superlubricity (also referred to as the state of vanishing friction or near-frictionless sliding).
		Jean Michel Martin and I feel that it is perhaps an opportune time to tackle this very important subject in a special symposium at the next World Tribology Congress - III to be held in Washington, DC-USA from September 12 to 16, 2005 (you may find further details at: http://www.conferencetoolbox.org/wtc05/).
		The main goal of this symposium is to highlight recent advances in achieving and understanding of superlubricity over broad length and time scales.
	sklt.tsinghua.edu.cn /staff/gdmember/jinys/email.txt (278 words)

	Nanotechnology: Science & Technology Essays - 2005
		Remember that the surfaces must be very smooth, so they can slip past each other; and very stiff, so the bumps don't push each other sideways and spring back; and the bumps must not line up, or they will interlock.
		Biological molecules are not stiff enough to use the superlubricity trick.
		Superlubricity may be counterintuitive to people who are accustomed to the high friction of most hard dry surfaces.
	www.crnano.org /essays05.htm (19187 words)

	Information Bridge: DOE Scientific and Technical Information - - Document #793063 (Site not responding. Last check: 2007-11-02)
		Specifically, the friction and wear coefficients of DLC films grown in plasmas with higher hydrogen-to-carbon ratios were much lower than films derived from source gases with lower hydrogen-to-carbon ratios.
		Fundamental tribological and surface analytical studies have led us to conclude that hydrogen (within the film, as well as on the sliding surfaces) is extremely important for the superlubricity and wearless sliding behavior of these films.
		Based on these studies, a mechanistic model is proposed to explain the superlow friction and wear properties of the new DLC films.
	www.osti.gov /bridge/product.biblio.jsp?osti_id=793063 (266 words)

	Robotic friction - WiseNano
		However, if the atoms do not line up, for example because one of the surfaces is turned at an angle, then the bumps will cancel out--assuming the construction is stiff enough that the bumps don't rearrange to fit between each other and let the surfaces squish together.
		This canceling, called "superlubricity," has been demonstrated in graphite.
		The demonstration of superlubricity, and also Zettl's work with freely sliding and rotating buckytubes, provides some reason for optimism.
	wise-nano.org /w/Robotic_friction (438 words)

	Friction at the nano-scale (February 2005) - Features - nanotechweb.org
		The possibility that phononic friction can be exceptionally small between two atomically incommensurate surfaces has been referred to as superlubricity by some researchers.
		This is unfortunate, since the "resistance" does not drop to zero, as in the case of superconductivity or superfluidity, but instead simply arises from low levels of phononic friction associated with the structural incompatibility of the sliding surfaces.
		The Leiden team captured a graphite flake on the end of a tungsten tip and measured the friction as it was slid along a crystalline graphite substrate (the contact area of the flake was estimated to be a mere 96 atoms).
	www.nanotechweb.org /articles/feature/4/2/1/1 (2869 words)

	Slippery Nanoworld
		This superlubricity was found to "survive" when the tip was pushed down with appreciable forces of several tens of nN.
		Forces exerted on the tip lead to deformations of the four thin arms, that are detected by four laser interferometers, indicated by the tapered green fibers (not drawn to scale).
		The results on graphite have led to the speculation that the excellent lubricating properties of graphite powder may be the result of superlubricity, the motion between lubricated surfaces actually taking place between graphite flakes, most of which are misaligned with respect to each other, therefore sliding with ultralow friction.
	www.europhysicsnews.com /full/31/article2/article2.html (1914 words)

	IngentaConnect Nanomechanical Studies of Superlubricity
		For the atomic and flake frictions, frictional force maps are compared between simulations and experiments, which can be explained by stick-slip motion of the tip apex atom and flake.
		For the graphite/C60/graphite system, superlubricity appears, where the maximum static frictional forces have finite values but denote that dynamical frictional forces are zero within the resolution of the experiment.
		It is clarified that fullerene intercalated graphite films exhibit ultralow average friction force, and excellent friction coefficients μ < 0.001.
	www.ingentaconnect.com /content/ben/cnano/2007/00000003/00000001/art00011 (264 words)

	Graphite - Article about Graphite (Site not responding. Last check: 2007-11-02)
		Other characteristics: thin flakes are flexible but inelastic, mineral can leave fl marks on hands and paper, conducts electricity, and displays superlubricity.
		Recent studies suggest that an effect called superlubricity can also account for this effect.
		The use of graphite is also limited by its tendency to facilitate pitting corrosion in some stainless steels, and to promote galvanic corrosion between dissimilar metals.
	yawiki.org /proc/Graphite (885 words)

	Nanotechnology Spotlight - Reducing friction at the nanoscale
		Researchers in Switzerland now describe a resonance-induced superlubricity, which also occurs in many natural phenomena from biological systems to the motion of tectonic plates.
		Compared to other techniques recently introduced to achieve reduced friction, the Swiss group's method is not restricted to extremely tiny loads or well-defined crystal surfaces and therefore should find better application in practical situations.
		Also, the method allows fast switching between a "superlubric" and a "normal" regime, where friction and dissipation are present.
	www.nanowerk.com /spotlight/spotid=1174.php (924 words)

	Friction at the nano-scale (February 2005) - Features - nanotechweb.org
		The possibility that phononic friction can be exceptionally small between two atomically incommensurate surfaces has been referred to as superlubricity by some researchers.
		This is unfortunate, since the "resistance" does not drop to zero, as in the case of superconductivity or superfluidity, but instead simply arises from low levels of phononic friction associated with the structural incompatibility of the sliding surfaces.
		The Leiden team captured a graphite flake on the end of a tungsten tip and measured the friction as it was slid along a crystalline graphite substrate (the contact area of the flake was estimated to be a mere 96 atoms).
	nanotechweb.org /articles/feature/4/2/1/1?rss=2.0 (2878 words)

	APS - 2005 APS March Meeting - Event - Superlubricity of a natural polysaccharide from the alga Porphyridium sp. (Site not responding. Last check: 2007-11-02)
		APS - 2005 APS March Meeting - Event - Superlubricity of a natural polysaccharide from the alga Porphyridium sp.
		Abstract: V31.00010 : Superlubricity of a natural polysaccharide from the alga Porphyridium sp.
		Using a surface forces apparatus we have studied the adhesive and lubrication forces of mica surfaces separated by a molecularly-thin, sub-nanometer, film of a high molecular weight (2.6 MDa) naturally occurring anionic polysaccharide adsorbed from aqueous solution.
	meetings.aps.org /Meeting/MAR05/Event/24654 (136 words)

	Abstract-Frenken (Site not responding. Last check: 2007-11-02)
		We have constructed a frictional force microscope (FFM) that is able to quantitatively track the forces between a sharp tip and a flat sample in three dimensions, with a friction force resolution as low as 15 pN, even under normal loads up to several tens of nN.
		We interpret this vanishing of the friction force as the first direct observation of "superlubricity": a special force cancellation phenomenon predicted for nano-scale contacts between stiff, incommensurate surfaces.
		This peculiar effect may also be the origin of the excellent lubricating properties of graphite in practical applications...
	www.science.uva.nl /research/wzi/colloquium/abs/abstract-frenken.htm (136 words)

	Vanishing Friction: How Close Are We? (Site not responding. Last check: 2007-11-02)
		Overall, our research has confirmed that carbon as an element is rather unique and offer the kind of flexibility that one needs in designing such novel coatings with superlow friciton and wear properties.
		This talk will provide an overview of the mechanistic understanding of superlubricity in such films.
		Examples of current and future tribological applications for such films will also be presented.
	ses.confex.com /ses/2004tm/techprogram/P1215.HTM (165 words)

	[No title]
		When the misalignment is sufficiently severe, the lateral forces on the C-atoms in the flake cancel, thereby dramatically reducing the total friction force.
		Friction is proven to vanish in the limiting case of zero velocity, in contrast to the suggestions of earlier simulations.
		A new phenomenon of "thermolubricity" is predicted to be an important alternative to the known "mechanistic" superlubricity: friction can be negligibly small in the cases when the surface corrugation is large enough to produce sizable friction in the framework of known mechanistic models.
	faculty.washington.edu /london/Lorentz/abstracts.html (5658 words)

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