Measuring and modeling thermal fluctuations at nanometer length scales

2002 ◽  
Vol 65 (5) ◽  
Author(s):  
R. M. Ralich ◽  
R. D. Ramsier ◽  
D. D. Quinn ◽  
C. B. Clemons ◽  
G. W. Young
Keyword(s):  
Thermal Fluctuations ◽  
Length Scales

scholarly journals STATISTICAL PHYSICS OF ISOTROPIC-GENESIS NEMATIC ELASTOMERS: I. STRUCTURE AND CORRELATIONS AT HIGH TEMPERATURES

2013 ◽  
Vol 27 (17) ◽  
pp. 1330012 ◽  
Author(s):  
BING-SUI LU ◽  
FANGFU YE ◽  
XIANGJUN XING ◽  
PAUL M. GOLDBART
Keyword(s):  
High Temperatures ◽  
Liquid Crystalline ◽  
Landau Theory ◽  
Thermal Fluctuations ◽  
Cross Linking ◽  
Chain Model ◽  
Length Scales ◽  
Nematic Elastomers ◽  
Temperature State ◽  
The Cross

Isotropic-genesis nematic elastomers (IGNEs) are liquid crystalline polymers (LCPs) that have been randomly, permanently cross-linked in the high-temperature state so as to form an equilibrium random solid. Thus, instead of being free to diffuse throughout the entire volume, as they would be in the liquid state, the constituent LCPs in an IGNE are mobile only over a finite, segment specific, length-scale controlled by the density of cross-links. We address the effects that such network-induced localization have on the liquid–crystalline characteristics of an IGNE, as probed via measurements made at high temperatures. In contrast with the case of uncross-linked LCPs, for IGNEs these characteristics are determined not only by thermal fluctuations but also by the quenched disorder associated with the cross-link constraints. To study IGNEs, we consider a microscopic model of dimer nematogens in which the dimers interact via orientation-dependent excluded volume forces. The dimers are, furthermore, randomly, permanently cross-linked via short Hookean springs, the statistics of which we model by means of a Deam–Edwards type of distribution. We show that at length-scales larger than the size of the nematogens this approach leads to a recently proposed, phenomenological Landau theory of IGNEs [Lu et al., Phys. Rev. Lett.108, 257803 (2012)], and hence predicts a regime of short-ranged oscillatory spatial correlations in the nematic alignment, of both thermal and glassy types. In addition, we consider two alternative microscopic models of IGNEs: (i) a wormlike chain model of IGNEs that are formed via the cross-linking of side-chain LCPs; and (ii) a jointed chain model of IGNEs that are formed via the cross-linking of main-chain LCPs. At large length-scales, both of these models give rise to liquid–crystalline characteristics that are qualitatively in line with those predicted on the basis of the dimer-and-springs model, reflecting the fact that the three models inhabit a common universality class.

scholarly journals Tiling a tubule: How increasing complexity improves the yield of self-limited assembly

2022 ◽  
Author(s):  
Thomas Erik Videbaek ◽  
Huang Fang ◽  
Daichi Hayakawa ◽  
Botond Tyukodi ◽  
Michael F Hagan ◽  
...  
Keyword(s):  
Self Assembly ◽  
Colloidal Particles ◽  
Thermal Fluctuations ◽  
Single Type ◽  
Bending Rigidity ◽  
Length Scales ◽  
Minimum Number ◽  
Limited Length ◽  
Multiple Species ◽  
Finite Bending

Abstract The ability to design and synthesize ever more complicated colloidal particles opens the possibility of self-assembling a zoo of complex structures, including those with one or more self-limited length scales. An undesirable feature of systems with self-limited length scales is that thermal fluctuations can lead to the assembly of nearby, off-target states. We investigate strategies for limiting off-target assembly by using multiple types of subunits. Using simulations and energetics calculations, we explore this concept by considering the assembly of tubules built from triangular subunits that bind edge to edge. While in principle, a single type of triangle can assemble into tubules with a monodisperse width distribution, in practice, the finite bending rigidity of the binding sites leads to the formation of off-target structures. To increase the assembly specificity, we introduce tiling rules for assembling tubules from multiple species of triangles. We show that the selectivity of the target structure can be dramatically improved by using multiple species of subunits, and provide a prescription for choosing the minimum number of subunit species required for near-perfect yield. Our approach of increasing the system’s complexity to reduce the accessibility of neighboring structures should be generalizable to other systems beyond the self-assembly of tubules.

Thermal Fluctuations of Freely Suspended Smectic-A Films from Mesoscopic to Molecular Length Scales

1997 ◽  
Vol 79 (18) ◽  
pp. 3439-3442 ◽  
Author(s):  
E. A. L. Mol ◽  
G. C. L. Wong ◽  
J. M. Petit ◽  
F. Rieutord ◽  
W. H. de Jeu
Keyword(s):  
Thermal Fluctuations ◽  
Length Scales ◽  
Smectic A ◽  
Molecular Length ◽  
Freely Suspended

An Analytical Thermodynamic Approach to Friction of Rubber on Ice

2012 ◽  
Vol 40 (2) ◽  
pp. 124-150
Author(s):  
Klaus Wiese ◽  
Thiemo M. Kessel ◽  
Reinhard Mundl ◽  
Burkhard Wies
Keyword(s):  
Coefficient Of Friction ◽  
Liquid Layer ◽  
Contact Area ◽  
Leading Edge ◽  
Viscous Friction ◽  
Analytical Approximation ◽  
Real Contact Area ◽  
Length Scales ◽  
Real Contact ◽  
Ice Surface

ABSTRACT The presented investigation is motivated by the need for performance improvement in winter tires, based on the idea of innovative “functional” surfaces. Current tread design features focus on macroscopic length scales. The potential of microscopic surface effects for friction on wintery roads has not been considered extensively yet. We limit our considerations to length scales for which rubber is rough, in contrast to a perfectly smooth ice surface. Therefore we assume that the only source of frictional forces is the viscosity of a sheared intermediate thin liquid layer of melted ice. Rubber hysteresis and adhesion effects are considered to be negligible. The height of the liquid layer is driven by an equilibrium between the heat built up by viscous friction, energy consumption for phase transition between ice and water, and heat flow into the cold underlying ice. In addition, the microscopic “squeeze-out” phenomena of melted water resulting from rubber asperities are also taken into consideration. The size and microscopic real contact area of these asperities are derived from roughness parameters of the free rubber surface using Greenwood-Williamson contact theory and compared with the measured real contact area. The derived one-dimensional differential equation for the height of an averaged liquid layer is solved for stationary sliding by a piecewise analytical approximation. The frictional shear forces are deduced and integrated over the whole macroscopic contact area to result in a global coefficient of friction. The boundary condition at the leading edge of the contact area is prescribed by the height of a “quasi-liquid layer,” which already exists on the “free” ice surface. It turns out that this approach meets the measured coefficient of friction in the laboratory. More precisely, the calculated dependencies of the friction coefficient on ice temperature, sliding speed, and contact pressure are confirmed by measurements of a simple rubber block sample on artificial ice in the laboratory.

Lossless Photon management – Optical design for manufacture at different length scales - NOLOSS - H2020

Impact ◽  
2018 ◽  
Vol 2018 (1) ◽  
pp. 48-50
Author(s):  
Toralf Scharf ◽  
Paul Urbach ◽  
Carsten Rockstuhl ◽  
Frank Setzpfand
Keyword(s):  
Optical Design ◽  
Length Scales ◽  
Design For Manufacture ◽  
Photon Management

Thermal fluctuations of non-motile magnetotactic bacteria in AC magnetic fields

2008 ◽  
Vol 44 (3) ◽  
pp. 223-236 ◽  
Author(s):  
K. Ērglis ◽  
L. Alberte ◽  
A. Cēbers
Keyword(s):  
Magnetic Fields ◽  
Magnetotactic Bacteria ◽  
Thermal Fluctuations
Sign in / Sign up

Export Citation Format

Share Document