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  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 25 November 2014, Vol.111(47), pp.16676-81
    Description: MXenes, a new family of 2D materials, combine hydrophilic surfaces with metallic conductivity. Delamination of MXene produces single-layer nanosheets with thickness of about a nanometer and lateral size of the order of micrometers. The high aspect ratio of delaminated MXene renders it promising nanofiller in multifunctional polymer nanocomposites. Herein, Ti3C2T(x) MXene was mixed with either a charged polydiallyldimethylammonium chloride (PDDA) or an electrically neutral polyvinyl alcohol (PVA) to produce Ti3C2T(x)/polymer composites. The as-fabricated composites are flexible and have electrical conductivities as high as 2.2 × 10(4) S/m in the case of the Ti3C2T(x)/PVA composite film and 2.4 × 10(5) S/m for pure Ti3C2T(x) films. The tensile strength of the Ti3C2T(x)/PVA composites was significantly enhanced compared with pure Ti3C2T(x) or PVA films. The intercalation and confinement of the polymer between the MXene flakes not only increased flexibility but also enhanced cationic intercalation,...
    Subject(s): 2d Material ; Mxene ; Composite ; Film ; Supercapacitor
    ISSN: 0027-8424
    E-ISSN: 1091-6490
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  • 2
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 29 May 2018, Vol.115(22), pp.5641-5646
    Description: There is significant variation in the reported magnitude and even the sign of [Formula: see text] shifts in thin polymer films with nominally the same chemistry, film thickness, and supporting substrate. The implicit assumption is that methods used to estimate [Formula: see text] in bulk materials are relevant for inferring dynamic changes in thin films. To test the validity of this assumption, we perform molecular simulations of a coarse-grained polymer melt supported on an attractive substrate. As observed in many experiments, we find that [Formula: see text] based on thermodynamic criteria (temperature dependence of film height or enthalpy) decreases with decreasing film thickness, regardless of the polymer-substrate interaction strength ε. In contrast, we find that [Formula: see text] based on a dynamic criterion (relaxation of the dynamic structure factor) also decreases with decreasing thickness when ε is relatively weak, but [Formula: see text] increases when ε exceeds the polymer-polymer...
    Subject(s): Film Dynamics ; Glass Transition ; Thin Polymer Film
    ISSN: 0027-8424
    E-ISSN: 1091-6490
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  • 3
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 7 August 2012, Vol.109(32), pp.12873-12877
    Description: 〈p〉A study of the surface energetics of the thinnest substrate-free liquid films, fluid molecular monolayer and multilayer smectic liquid crystal films suspended in air, is reported. In films having monolayer and multilayer domains, the monolayer areas contract, contrary to predictions from the van der Waals disjoining pressure of thin uniform slabs. This discrepancy is accounted for by modeling the environmental asymmetry of the surface layers in multilayer films, leading to the possibility that preferential end-for-end polar ordering of the rod shaped molecules can reduce the surface energy of multilayers relative to that of the monolayer, which is inherently symmetric.〈/p〉
    Subject(s): Fluid Film ; Liquid Crystals
    ISSN: 00278424
    E-ISSN: 10916490
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  • 4
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 8 November 2011, Vol.108(45), pp.18227-18232
    Description: The buckling and wrinkling of thin films has recently seen a surge of interest among physicists, biologists, mathematicians, and engineers. This activity has been triggered by the growing interest in developing technologies at ever-decreasing scales and the resulting necessity to control the mechanics of tiny structures, as well as by the realization that morphogenetic processes, such as the tissue-shaping instabilities occurring in animal epithelia or plant leaves, often emerge from mechanical instabilities of cell sheets. Although the most basic buckling instability of uniaxially compressed plates was understood by Euler more than two centuries ago, recent experiments on nanometrically thin (ultrathin) films have shown Significant deviations from predictions of standard buckling theory. Motivated by this puzzle, we introduce here a theoretical model that allows for a systematic analysis of wrinkling in sheets far from their instability threshold. We focus on the simplest extension of Euler buckling that exhibits wrinkles of finite length--a sheet under axisymmetric tensile loads. The first study of this geometry, which is attributed to Lame, allows us to construct a phase diagram that demonstrates the dramatic variation of wrinkling patterns from near-threshold to far-from-threshold conditions. Theoretical arguments and comparison to experiments show that the thinner the sheet is, the smaller is the compressive load above which the far-from-threshold regime emerges. This observation emphasizes the relevance of our analysis for nanomechanics applications. pattern formation | thin-film buckling doi/ 10.1073/pnas.1108553108
    Subject(s): Pattern Formation ; Thin-Film Buckling
    ISSN: 00278424
    E-ISSN: 10916490
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  • 5
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 12 July 2016, Vol.113(28), pp.7711-6
    Description: The current simple nanofluid flooding method for tertiary or enhanced oil recovery is inefficient, especially when used with low nanoparticle concentration. We have designed and produced a nanofluid of graphene-based amphiphilic nanosheets that is very effective at low concentration. Our nanosheets spontaneously approached the oil-water interface and reduced the interfacial tension in a saline environment (4 wt % NaCl and 1 wt % CaCl2), regardless of the solid surface wettability. A climbing film appeared and grew at moderate hydrodynamic condition to encapsulate the oil phase. With strong hydrodynamic power input, a solid-like interfacial film formed and was able to return to its original form even after being seriously disturbed. The film rapidly separated oil and water phases for slug-like oil displacement. The unique behavior of our nanosheet nanofluid tripled the best performance of conventional nanofluid flooding methods under similar conditions.
    Subject(s): Amphiphilic Janus Nanosheets ; Climbing Film ; Enhanced Oil Recovery ; Interfacial Film ; Nanofluid Flooding
    ISSN: 0027-8424
    E-ISSN: 1091-6490
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  • 6
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 16 August 2016, Vol.113(33), pp.9210-5
    Description: When touched, a glass plate excited with ultrasonic transverse waves feels notably more slippery than it does at rest. To study this phenomenon, we use frustrated total internal reflection to image the asperities of the skin that are in intimate contact with a glass plate. We observed that the load at the interface is shared between the elastic compression of the asperities of the skin and a squeeze film of air. Stroboscopic investigation reveals that the time evolution of the interfacial gap is partially out of phase with the plate vibration. Taken together, these results suggest that the skin bounces against the vibrating plate but that the bounces are cushioned by a squeeze film of air that does not have time to escape the interfacial separation. This behavior results in dynamic levitation, in which the average number of asperities in intimate contact is reduced, thereby reducing friction. This improved understanding of the physics of friction reduction provides key guidelines for designing...
    Subject(s): Acoustic ; Biotribology ; Haptics ; Roughness ; Squeeze Film ; Friction ; Fingers -- Physiology ; Touch -- Physiology
    ISSN: 0027-8424
    E-ISSN: 1091-6490
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  • 7
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 03 October 2017, Vol.114(40), pp.10601-10605
    Description: Nanometrically thin glassy films depart strikingly from the behavior of their bulk counterparts. We investigate whether the dynamical differences between a bulk and thin film polymeric glass former can be understood by differences in local microscopic structure. Machine learning methods have shown that local structure can serve as the foundation for successful, predictive models of particle rearrangement dynamics in bulk systems. By contrast, in thin glassy films, we find that particles at the center of the film and those near the surface are structurally indistinguishable despite exhibiting very different dynamics. Next, we show that structure-independent processes, already present in bulk systems and demonstrably different from simple facilitated dynamics, are crucial for understanding glassy dynamics in thin films. Our analysis suggests a picture of glassy dynamics in which two dynamical processes coexist, with relative strengths that depend on the distance from an interface. One of...
    Subject(s): Glass ; Machine Learning ; Thin Film
    ISSN: 0027-8424
    E-ISSN: 1091-6490
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  • 8
    Language: English
    In: Surface Science, February 2012, Vol.606(3-4), pp.456-460
    Description: We studied the atomic arrangements and the phase diagram of two-dimensional (2D) Bi–Sn binary films on Rh(111) with low-energy electron diffraction and scanning tunneling microscopy (STM). The 2D binary films exhibited (“2”×√3)-(Bi,Sn), (√7×√7)R19°-(Bi,Sn), and (7×3√3)-(Bi,Sn) structures, depending on the compositional ratio of Bi and Sn. Atomically resolved STM images revealed that the binary films formed a BiSn3 ordered alloy for the (√7×√7)R19°-(Bi,Sn) structure and a solid solution alloy for the (“2”×√3)-(Bi,Sn) structure. The atomic configuration for the (7×3√3)-(Bi,Sn) structure was closely related to that of (√7×√7) R19°-(Bi,Sn). ► The 2D solid solution alloy was formed when Sn compositional ratio is above 80%. ► The 2D film changed from twofold to sixfold structures as Bi composition increased. ► The 2D ordered alloy of BiSn3 was formed on Rh(111).
    Subject(s): 2d Film ; 2d Film ; Chemistry ; Physics
    ISSN: 0039-6028
    E-ISSN: 1879-2758
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  • 9
    In: Management science, 2013, Vol.59(3), p.733
    Subject(s): Film
    ISSN: 0025-1909
    Source: wiso Wirtschaftswissenschaften (GBI-Genios Deutsche Wirtschaftsdatenbank GmbH) 〈img src="http://exlibris-pub.s3.amazonaws.com/wiso_logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 10
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 17 March 2015, Vol.112(11), pp.3280-4
    Description: When a fast-moving drop impacts onto a smooth substrate, splashing will be produced at the edge of the expanding liquid sheet. This ubiquitous phenomenon lacks a fundamental understanding. Combining experiment with model, we illustrate that the ultrathin air film trapped under the expanding liquid front triggers splashing. Because this film is thinner than the mean free path of air molecules, the interior airflow transfers momentum with an unusually high velocity comparable to the speed of sound and generates a stress 10 times stronger than the airflow in common situations. Such a large stress initiates Kelvin-Helmholtz instabilities at small length scales and effectively produces splashing. Our model agrees quantitatively with experimental verifications and brings a fundamental understanding to the ubiquitous phenomenon of drop splashing on smooth surfaces.
    Subject(s): Kelvin–Helmholtz Instability ; Drop Impact ; Splash ; Thin Air Film
    ISSN: 0027-8424
    E-ISSN: 1091-6490
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