Anisotropic domains with 180° periodicity are known to be universally present on graphene as well as on other two-dimensional (2D) crystals. The physical origin of the domains and the mechanism of its anisotropy are, however, still unclear. Here, by employing in-plane elastic imaging by torsional resonance atomic force microscopy (TR-AFM), we demonstrate that the observed domains on graphene are of in-plane elastic (shear) anisotropy but not of friction anisotropy as commonly believed. Our results also support that the anisotropic domains originate from self-assembled environmental adsorbates on graphene surfaces. The more densely packed backbone of the highly ordered molecules within a domain defines the major axis of the shear anisotropy of the latter. This work suggests a quantitative understanding of the characteristics of anisotropic domains on 2D materials. It also demonstrates TR-AFM as a powerful tool to study the in-plane elastic anisotropy of materials, including organic molecular crystals.
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http://dx.doi.org/10.1021/acsnano.4c04368 | DOI Listing |
Phys Chem Chem Phys
December 2024
Yunnan Key Laboratory of Electromagnetic Materials and Devices, National Center for International Research on Photoelectric and Energy Materials, School of Materials and Energy, Yunnan University, Kunming, 650091, P. R. China.
Multifunctional materials with outstanding performance have enormous potential applications in the next generation of nanodevices. Using first principles calculations, we design a series of multifunctional two-dimensional materials in monolayer αh-GeSe (, = 1, 2) that combine auxeticity and piezoelectricity. Due to the similar local structures of α-GeSe and h-GeSe, monolayer αh-GeSe can be designed through the combination of these two materials.
View Article and Find Full Text PDFAdv Sci (Weinh)
December 2024
Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, 999077, China.
Math Mech Solids
November 2024
Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada.
We derive a closed-form solution to the plane strain problem of a partially debonded rigid elliptical inclusion in which the debonded portion is filled with a liquid slit inclusion when the infinite isotropic elastic matrix is subjected to uniform remote in-plane stresses. The original boundary value problem is reduced to a Riemann-Hilbert problem with discontinuous coefficients, and its analytical solution is derived. By imposing the incompressibility condition of the liquid slit inclusion and balance of moment on a circular disk of infinite radius, we obtain a set of two coupled linear algebraic equations for the two unknowns characterizing the internal uniform hydrostatic tension within the liquid slit inclusion and the rigid body rotation of the rigid elliptical inclusion.
View Article and Find Full Text PDFRev Sci Instrum
October 2024
School of Mechanical and Electrical Engineering, Henan University of Technology, Zhengzhou 450001, China.
The cylindrical ultrasonic motor, noted for its straightforward design, ease of miniaturization, and high precision, has significant potential in fields such as optics, healthcare, and precision engineering. However, miniaturization presents challenges, including diminished output force and complications in applying preloading stress. To address the reduced output force, this study presents a dual-stator, high-thrust cylindrical linear ultrasonic motor.
View Article and Find Full Text PDFJ Acoust Soc Am
October 2024
Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA.
Bistatic laboratory measurements are presented for acoustic scattering from both smooth and rough elastic cylinders insonified by directional spherical waves. A scattering model, accounting for incident directional spherical waves while assuming negligible end effects, was derived in a previous article [Mursaline, Stanton, Lavery, and Fischell, J. Acoust.
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