A theoretical analysis of the surface dependent binding, peeling and folding of graphene on single crystal copper

The binding, peeling and folding behavior of graphene on different surfaces of single crystal copper were examined theoretically. We show that the binding energy is the highest on the Cu(111), and follows the order of Cu(111) > (100) > (110) > (112). Conventional theory is capable of capturing the dynamic process of graphene peeling seen from molecular dynamics simulations. We show that the number of graphene layers on Cu surfaces could be distinguished by performing simple peeling tests. Further investigation of the folding/unfolding of graphene on Cu surfaces shows that Cu(111) favors the growth of monolayer graphene. These observations on the interaction between graphene with single crystal Cu surfaces might provide guidelines for improving graphene fabrication

第十八届美国理论与应用力学大会总结

1会议概况2018年6月5—9日,第18届美国理论与应用力学大会(18th U.S. National Congress of Theoretical and Applied Mechanics, USNCTAM2018)在美国芝加哥召开.本次大会由美国力学国家委员会和中国力学学会联合主办,旨在探讨和交流近四年世界范围内在理论和应用力学领域的基础研究、创新技术的最新进展,吸引了来自世界各地的近千名专家学

Tunable Mechanical Behavior of Carbon Nanoscroll Crystals Under Uniaxial Lateral Compression

A theoretical model is developed to investigate the mechanical behavior of closely packed carbon nanoscrolls (CNSs), the so-called CNS crystals, subjected to uniaxial lateral compression/ decompression. Molecular dynamics simulations are performed to verify the model predictions. It is shown that the compression behavior of a CNS crystal can exhibit strong hysteresis that may be tuned by an applied electric field. The present study demonstrates the potential of CNSs for applications in energy-absorbing materials as well as nanodevices, such as artificial muscles, where reversible and controllable volumetric deformations are desired

c-axis preferential orientation of hydroxyapatite accounts for the high wear resistance of the teeth of black carp (Mylopharyngodon piceus)

Biological armors such as mollusk shells have long been recognized and studied for their values in inspiring novel designs of engineering materials with higher toughness and strength. However, no material is invincible and biological armors also have their rivals. In this paper, our attention is focused on the teeth of black carp (Mylopharyngodon piceus) which is a predator of shelled mollusks like snails and mussels. Nanoscratching test on the enameloid, the outermost layer of the teeth, indicates that the natural occlusal surface (OS) has much higher wear resistance compared to the other sections. Subsequent X-ray diffraction analysis reveals that the hydroxyapatite (HAp) crystallites in the vicinity of OS possess c-axis preferential orientation. The superior wear resistance of black carp teeth is attributed to the c-axis preferential orientation of HAp near the OS since the (001) surface of HAp crystal, which is perpendicular to the c-axis, exhibits much better wear resistance compared to the other surfaces as demonstrated by the molecular dynamics simulation. Our results not only shed light on the origin of the good wear resistance exhibited by the black carp teeth but are of great value to the design of engineering materials with better abrasion resistance

基于磁电复合材料的四态存储器

四态存储器是一种能够在一个存储单元内记录四种信息状态的新型存储器.采用磁电复合材料Co/PZT制作了一个四态存储器的存储单元原型,该存储单元的磁电输出信号随外磁场变化存在明显的滞回现象.根据磁电滞回现象,提出了施加偏置磁场的读取原理,实际测试结果给出了区别明显的15.8μV,?4.4μV,5.5μV,?11.3μV四种信号,初步演示了磁电复合材料用作四态存储器的可行性.国家自然科学基金(批准号:50571084); 国家高技术研究发展计划(编号:2006AA03Z101)资助项目

纳米颗粒形状对其在肠胃道黏液中扩散的影响

组织黏液(mucus)可以用来保护肺部、肠胃道、眼睛和其他的黏膜表面,它是一种粘弹性和带黏性的胶。许多外来的颗粒物质,包括用来载带药物的颗粒载体,都会由于黏液的空间障碍作用或黏附作用而陷在人体的黏液层中。陷入黏液层的颗粒会随着黏液的持续分泌更新而被清除。如果载带药物的颗粒可以扩散通过黏液层,并将药物运送至黏膜组织,将会更有效地治疗许多令人衰弱的疾病,并伴随着更小的副作用。通过实验的方法研究不

Surface hydrophilicity mediated migration of nano/microparticles under temperature gradient in a confined space

Hypothesis: Particle transport by a temperature gradient is prospective in many biomedical applications. However, the prevalence of boundary confinement in practical use introduces synergistic effects of thermophoresis and thermo osmosis, causing controversial phenomena and great difficulty in understanding the mechanisms. Experiments: We developed a microfluidic chip with a uniform temperature gradient and switchable sub strate hydrophilicity to measure the migrations of various particles (d = 200 nm 2 lm), through which the effects of particle thermophoresis and thermo osmotic flow from the substrate surface were decou pled. The contribution of substrate hydrophilicity on thermo osmosis was examined. Thermophoresis was measured to clarify its dependence on particle size and hydrophilicity. Findings: This paper reports the first experimental evidence of a large enthalpy dependent thermo osmotic mobility chi similar to Delta H on a hydrophobic polymer surface, which is 1 2 orders of magnitude larger than that on hydrophilic surfaces. The normalized Soret coefficient for polystyrene particles, ST/ d = 18.0 K 1 mu m( 1), is confirmed to be constant, which helps clarify the controversy of the size dependence. Besides, the Soret coefficient of hydrophobic proteins is approximately four times larger than that of hydrophilic extracellular vesicles. These findings suggest that the intrinsic slip on the hydrophobic surface could enhance both surface thermoosmosis and particle thermophoresis. (c) 2023 Elsevier Inc. All rights reserved

Cooperative entry of nanoparticles into the cell

Interaction of nanoparticles (NPs) with cell membrane is a crucial issue in studying drug delivery, photodynamic therapy system and cytotoxicity. Single NP with relatively small size cannot be fully wrapped by the cell membrane, which prohibits its uptake. One feasible way is cooperative entry, i.e., recruiting and assembling multiple small NPs to form a larger NP cluster to enter into a cell. In this work, we present theoretical analysis about the cooperative entry of multiple NPs. Through free energy calculation we investigate how the NPs׳ size, shape, interval and NP/cell interfacial binding energy influence the feasibility of entry. Interestingly we find that the cooperative entry of oblate ellipsoidal NPs can get larger energy compensation than individual ones as well as spherical ones. We also propose that soft NPs have preference in cooperative entry of the cell. Our work can be used to actively design and transfer NPs in applications such as drug delivery as well as to understand the shape effect on toxic mechanism of ellipsoidal NPs.</span