Superlubricity - Revision history

Apm: Category:Surprising facts

2026-03-29T20:34:42Z

← Older revision		Revision as of 22:34, 29 March 2026
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	[[Category: Technology level III]]		[[Category: Technology level III]]
	[[Category: Technology level ~~III~~]]		[[Category: Technology level II]]
			[[Category:Surprising facts]]

Apm: added section = Nanosystems section to decypher (Page 292) = (mabe move to friction in gem-gum-tech page later?)

2025-11-15T12:35:03Z

added section = Nanosystems section to decypher (Page 292) = (mabe move to friction in gem-gum-tech page later?)

← Older revision		Revision as of 14:35, 15 November 2025
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	Some of the the moving [[examples of diamondoid molecular machine elements]] <br>		Some of the the moving [[examples of diamondoid molecular machine elements]] <br>
	feature tuned incommensurability and thus superlubricity.		feature tuned incommensurability and thus superlubricity.

			= Nanosystems section to decypher (Page 292) =

			10.4.6. Mechanisms of energy dissipation <br>
			c. Band-stiffness scattering <br>

			"The parameter <math>\Delta k_a / k_a</math> can be estimated from variations in the stiffness of nonbonded interactions between rows of equally spaced atoms as a function of their offset from alignment. Like many differential quantities, it is strongly dependent on the spacial frequencies involved. For first-row atoms (taking carbon as a model) <math>\Delta k_a / k_a \approx 0.3 \ to \ 0.4</math> (at a stifness-per-atom of 1 and 10 N/m, respectively) where d<sub>a</sub> = 0.25nm, and ~0.001 to 0.003 where d<sub>a</sub> = 0.125 nm.
			'''This vaue of d<sub>a</sub> cannot be physicaly achieved in coplanar rings, but it correctly models a ring sandwitched between two other equidistant rings having d<sub>a</sub> = 0.25 nm and a rotational offset of 0.125nm.'''"

	= External links =		= External links =

Apm: /* Rods in sleeves */

2025-11-15T12:07:27Z

Rods in sleeves

← Older revision		Revision as of 14:07, 15 November 2025
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	Challenges:		Challenges:
	* Using the same material for rod and sleeve can lead to pretty much the same spacing and no good superlubrication.		* Using the same material for rod and sleeve (and the same crystallographic sliding direction) can lead to pretty much the same spacing and no good superlubrication.
	* Getting a fit of just the right tightness with a compact sleeve around a thin reciprocative rod may be more difficult than getting just the right fit with a big stator sleeve around a big diameter rotor. Bigger loops can be finer adjusted in a relative sense.		* Getting a fit of just the right tightness with a compact sleeve around a thin reciprocative rod may be more difficult than getting just the right fit with a big stator sleeve around a big diameter rotor. Bigger loops can be finer adjusted in a relative sense.

Apm: /* Ditching the trapdoors */ more precise

2025-11-15T12:06:39Z

Ditching the trapdoors: more precise

← Older revision		Revision as of 14:06, 15 November 2025
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	🪤 No, '''superlubricity is not the general absence of friction''' and not even about vanishingly small friction <br>		🪤 No, '''superlubricity is not the general absence of friction''' and not even about vanishingly small friction <br>
	it is particularly about the '''~~absence~~ of static friction'''. And maybe about quickly falling friction when decreasing speed. <br>		it is particularly about the '''very small level of static friction''' posibly even total absence in special cases. <br>
			And maybe about quickly falling friction when decreasing speed. <br>

	At speeds that would be considered modeate for macroscale bearings friction can actually be quite high. <br>		At speeds that would be considered modeate for macroscale bearings friction can actually be quite high. <br>

Apm: /* activation of vdW suck-in */

2025-11-15T12:04:31Z

activation of vdW suck-in

← Older revision		Revision as of 14:04, 15 November 2025
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	* The holding force of the remnant wavyness of the PES (potential energy surface) falls below the force of [[vdW suck-in]]		* The holding force of the remnant wavyness of the PES (potential energy surface) falls below the force of [[vdW suck-in]]

	== ~~activation~~ of [[vdW suck-in]] ==		== Activation of [[vdW suck-in]] ==

	This is …		This is …

Apm: /* Thresholds? */ added == activation of vdW suck-in ==

2025-11-15T12:01:33Z

Thresholds?: added == activation of vdW suck-in ==

@@ Line 104: / Line 104: @@
 * The waviness of the energy over the turning angle is exactly equal to the thermal energy per degree of freedom <br>(this is temperature dependent, but a constant for 300K room temperature)
 * The interface is at the threshold to [[snapback]]
 == Thermal activation energy - vs - Angular energy waviness ==

Apm: /* Stressed and strained rings */

2025-11-15T11:39:03Z

Stressed and strained rings

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	Incommensurality tends to fall out by itself for smaller rings. <br>		Incommensurality tends to fall out by itself for smaller rings. <br>
	Some symmetry considerations can be made for balanced behaviour. <br>		Some symmetry considerations can be made for balanced behaviour. <br>
	{{wikitodo\|Add more discussion here.}}		{{wikitodo\|Add more discussion here. Particularly conent from an old article (only printout left).}}

	= Superlubricating crystolecule machine elements =		= Superlubricating crystolecule machine elements =

Apm: /* Design principles */ added subsequent section: == Stressed and strained rings ==

2025-11-15T11:38:12Z

Design principles: added subsequent section: == Stressed and strained rings ==

← Older revision		Revision as of 13:38, 15 November 2025
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	= Design principles =		= Design principles =


	== Non-stressed non-strained [[crystolecules]] for linear bearings ==		== Non-stressed non-strained [[crystolecules]] for linear bearings ==
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	– The sliding-rail-segments must notably stronger vdW bond to housing matrix base (and themselves) than to the slider-rod. <br>		– The sliding-rail-segments must notably stronger vdW bond to housing matrix base (and themselves) than to the slider-rod. <br>
	… otherwise the sliding-rail-segment may be pulled in to be locally commensurate with the slider-rod. <br>		… otherwise the sliding-rail-segment may be pulled in to be locally commensurate with the slider-rod. <br>

			== Stressed and strained rings ==

			Incommensurality tends to fall out by itself for smaller rings. <br>
			Some symmetry considerations can be made for balanced behaviour. <br>
			{{wikitodo\|Add more discussion here.}}

	= Superlubricating crystolecule machine elements =		= Superlubricating crystolecule machine elements =

Apm: /* Main power dissipation mechanisms */ basic sketch

2025-11-15T11:27:59Z

Main power dissipation mechanisms: basic sketch

← Older revision		Revision as of 13:27, 15 November 2025
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	Main article: [[Friction mechanisms]]		Main article: [[Friction mechanisms]]

			= Design principles =


			== Non-stressed non-strained [[crystolecules]] for linear bearings ==

			There are a few options to get good [[incommensurability]] for superlubric iterfaces.

			'''Crystal axis mismatching:''' <br>
			Intentional parallel alignment of diffenent crystal axis directions for the sliding-axis. <br>
			For cubic systems this gives basic simplemost pairings and respective incommensuralities of: <br>
			<100>+<110> 1/√2, <110>+<111> 1/√3, <111>+<100> √3/√2 <br>
			Side-note: Sliding-rods for the <111> directions can not have right angles <br>
			in the cross sectional shape unless going to higher miller indices for the sliding-rod or sliding-rail faces. <br>
			I.e. not just {110} faces (which only alow for triangles and hexagons as crosssections) but also {210} faces. <br>
			Side-note: Sliding rods or rails in <110> directiin can inly be rectangular not square which can complicate design.

			'''Lattice mismatch material pairing:''' <br>
			Using two diffeent materials with mismatchig lattices <br>
			like e.g. [[lonsdaleite]] and hexagonal [[moissanite]] <br>
			this allows one to pair the same crystal axes parallely <br>
			in sliding direction and to still gain incommesurability. <br>
			An issue here is that while V-groove self centering for the sliding-rail <br>
			works across different lattice spacings <br>
			the '''W-groove self centering method is not applicable''' <br>
			as the spacing of the two peaks or two troughs always mismatch between the materials. <br>

			'''Incommensuralization spacer-shims''' <br>
			Using spacers to do <br>
			– crystal axis mismatching and/or <br>
			– lattice mismatch material pairing. <br>
			One side should be locke in place <br>
			e.g. by [[inset holes]] or by [[W groove self centering]] <br>
			transversal to sliding direction. <br>

			'''Incomensurally spaced rail segments:''' <br>
			Transversal to sliding direction spaced out placement <br>
			of sliding rail segments. <br>
			e.g. by [[inset holes]] or [[W groove self centering]] <br>
			could be used but this may just shift the problem. <br>

			'''Nonbonded interface commensurality breaking:''' <br>
			Using non-bonded interface-connections to introcudce <br>
			overall noncomensurality over longer length ranges. <br>
			Nontrivial constraints:
			– The sliding-rail-segments lengths must be shorther than the slider-rod. <br>
			… otherwise the rod will go commensurate whenever fully on just one rail segment <br>
			– The sliding-rail-segments must notably stronger vdW bond to housing matrix base (and themselves) than to the slider-rod. <br>
			… otherwise the sliding-rail-segment may be pulled in to be locally commensurate with the slider-rod. <br>

	= Superlubricating crystolecule machine elements =		= Superlubricating crystolecule machine elements =

Apm: /* Friction from dynamic drag? */

2025-11-06T15:54:14Z

Friction from dynamic drag?

← Older revision		Revision as of 17:54, 6 November 2025
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	It is the remnant friction that remains in a well designed bearing.		It is the remnant friction that remains in a well designed bearing.

	Oddly simulations of nanotube bearings (see math on page [[Friction in gem-gum technology]]) are quite a bit above the point of dominance of shear-reflection drag. And that despite this being a quite conservative (pessimistic) estimation for levels of drag.		Oddly simulations of nanotube bearings (see math on page [[Friction in gem-gum technology]]) <br>
			are quite a bit above the point of dominance of shear-reflection drag. <br>
			And that despite this being a quite conservative (pessimistic) estimation for levels of drag.

	{{todo\|Resolve the many not unrelevant mysteries here. More reading and thinking needed.}}		{{todo\|Resolve the many not unrelevant mysteries here. More reading and thinking needed.}}