Homogenization of surface energy and elasticity for highly rough surfaces

2021 ◽  
pp. 1-31
Author(s):  
Dajla Neffati ◽  
Yashashree Kulkarni
Keyword(s):  
Surface Energy ◽  
Self Assembly ◽  
Materials Science ◽  
Rough Surfaces ◽  
Surface Elasticity ◽  
Volume Ratio ◽  
Perturbation Approach ◽  
Homogenization Approach ◽  
Physical Response ◽  
The Impact

Abstract Surface energy plays a central role in several phenomena pertaining to nearly all aspects of materials science. This includes phenomena such as self-assembly, catalysis, fracture, void growth, and microstructural evolution among others. In particular, due to the large surface-to-volume ratio, the impact of surface energy on the physical response of nanostructures is nothing short of dramatic. How does the roughness of a surface renormalize the surface energy and associated quantities such as surface stress and surface elasticity? In this work, we attempt to address this question by using a multi-scale asymptotic homogenization approach. In particular, the novelty of our work is that we consider highly rough surfaces, reminiscent of experimental observations, as opposed to gentle roughness that is often treated by using a perturbation approach. We find that softening of a rough surface is significantly underestimated by conventional approaches. In addition, our approach naturally permits the consideration of bending resistance of a surface, consistent with the Steigmann-Ogden theory, in sharp contrast to the surfaces in the Gurtin-Murdoch surface elasticity theory that do not offer flexural resistance.

Elastic Energy of Surfaces and Residually Stressed Solids: An Energy Approach for the Mechanics of Nanostructures

2015 ◽  
Vol 82 (1) ◽  
Author(s):  
Xiang Gao ◽  
Daining Fang
Keyword(s):  
Surface Energy ◽  
Elastic Energy ◽  
Surface Stress ◽  
Strain Energy ◽  
Surface Effect ◽  
Surface Elasticity ◽  
Small Deformation ◽  
Energy Approach ◽  
Residual Surface Stress ◽  
The Impact

The surface energy plays a significant role in solids and structures at the small scales, and an explicit expression for surface energy is prerequisite for studying the nanostructures via energy methods. In this study, a general formula for surface energy at finite deformation is constructed, which has simple forms and clearly physical meanings. Next, the strain energy formulas both for isotropic and anisotropic surfaces under small deformation are derived. It is demonstrated that the surface elastic energy is also dependent on the nonlinear Green strain due to the impact of residual surface stress. Then, the strain energy formula for residually stressed elastic solids is given. These results are instrumental to the energy approach for nanomechanics. Finally, the proposed results are applied to investigate the elastic stability and natural frequency of nanowires. A deep analysis of these two examples reveals two length scales characterizing the significance of surface energy. One is the critical length of nanostructures for self-buckling; the other reflects the competition between residual surface stress and surface elasticity, indicating that the surface effect does not always strengthen the stiffness of nanostructures. These results are conducive to shed light on the importance of the residual surface stress and the initial stress in the bulk solids.

Coupled Effect of Surface Energy and Size Effect on the Static and Dynamic Pull-In Instability of Narrow Nano-Switches

2015 ◽  
Vol 07 (04) ◽  
pp. 1550064 ◽  
Author(s):  
Ali Koochi ◽  
Hossein Hosseini-Toudeshky
Keyword(s):  
Surface Energy ◽  
Size Effect ◽  
Couple Stress Theory ◽  
Surface Elasticity ◽  
Theoretical Models ◽  
Stress Theory ◽  
Small Width ◽  
Narrow Width ◽  
Casimir Attraction ◽  
The Impact

In this paper, the generalized differential quadrature (GDQ) method is employed to investigate the static and dynamic pull-in instability of nano-switches with small width/height ratio. For nano-switches with slender narrow-width beam elements, the corrections due to surface layer, external forces and size effect are crucial. So the couple-stress theory combined with the Gurtin–Murdoch surface elasticity is employed to incorporate the coupled effects of size phenomena and surface energy. In addition, the model accounts for the external force corrections by incorporating the impact of narrow width on the distribution of Casimir attraction, van der Waals force and the fringing field. The effects of the above-mentioned corrections on the static and dynamic pull-in parameters are demonstrated. The results from the modified model are compared with those from conventional parallel beam-plate models in the literature. It is shown that the corrections significantly affect the pull-in parameters of the narrow-width switches and hence, cannot be ignored in theoretical models. For wide switches, the results of the proposed model approach to those of the conventional models.

Investigation of Au SAMs Photoclick Derivatization by PM-IRRAS

2019 ◽  
Author(s):  
Mark Workentin ◽  
François Lagugné-Labarthet ◽  
Sidney Legge
Keyword(s):  
Cell Adhesion ◽  
Self Assembly ◽  
Materials Science ◽  
Fibroblast Cell ◽  
Fine Tuning ◽  
Chemical System ◽  
Infrared Reflection ◽  
Assembled Monolayers ◽  
One Step ◽  
High Degree

In this work we present a clean one-step process for modifying headgroups of self-assembled monolayers (SAMs) on gold using photo-enabled click chemistry. A thiolated, cyclopropenone-caged strained alkyne precursor was first functionalized onto a flat gold substrate through self-assembly. Exposure of the cyclopropenone SAM to UV-A light initiated the efficient photochemical decarbonylation of the cyclopropenone moiety, revealing the strained alkyne capable of undergoing the interfacial strain-promoted alkyne-azide cycloaddition (SPAAC). Irradiated SAMs were derivatized with a series of model azides with varied hydrophobicity to demonstrate the generality of this chemical system for the modification and fine-tuning of the surface chemistry on gold substrates. SAMs were characterized at each step with polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) to confirm successful functionalization and reactivity. Furthermore, to showcase the compatibility of this approach with biochemical applications, cyclopropenone SAMs were irradiated and modified with azide-bearing cell adhesion peptides to promote human fibroblast cell adhesion, then imaged by live cell fluorescence microscopy. Thus, the “photoclick” methodology reported here represents an improved, versatile, catalyst-free protocol that allows for a high degree of control over the modification of material surfaces, with applicability in materials science as well as biochemistry.<br>

Evaluation of Nanotechniques and Conventional Techniques for the Removal of Dioxins

2018 ◽  
Vol 9 (1) ◽  
pp. 79-84
Author(s):  
Vaishali V. Shahare ◽  
Rajni Grover ◽  
Suman Meena
Keyword(s):  
Soil Sample ◽  
Human Health ◽  
Surface Area ◽  
Contaminated Soil ◽  
Conventional Treatment ◽  
Volume Ratio ◽  
Soil Samples ◽  
Dioxins And Furans ◽  
Palladized Iron ◽  
The Impact

Background: The persistent dioxins/furans has caused a worldwide concern as they influence the human health. Recent research indicates that nonmaterial may prove effective in the degradation of Dioxins/furans. The nanomaterials are very reactive owing to their large surface area to volume ratio and large number of reactive sites. However, nanotechnology applications face both the challenges and the opportunities to influence the area of environmental protection. Objective: i) To study the impact of oil mediated UV-irradiations on the removal of 2,3,7,8-TCDD, 2,3,7,8-TCDF, OCDD and OCDF in simulated soil samples. ii) To compare the conventional treatment methods with the modern available nanotechniques for the removal of selected Dioxins/furans from soil samples. Methods: The present work has investigated an opportunity of the degradation of tetra and octachlorinated dioxins and furans by using oil mediated UV radiations with subsequent extraction of respective dioxins/furans from soils. The results have been compared with the available nanotechniques. Results: The dioxin congeners in the simulated soil sample showed decrease in concentration with the increase in the exposure time and intensity of UV radiations. The dechlorination of PCDD/Fs using palladized iron has been found to be effective. Conclusion: Both the conventional methods and nanotechnology have a dramatic impact on the removal of Dioxins/furans in contaminated soil. However, the nanotechniques are comparatively costlier and despite the relatively high rates of PCDDs dechlorination by Pd/nFe, small fraction of the dioxins are recalcitrant to degradation over considerable exposure times.

Novel Applications of Nanotechnology in Controlling HIV and HSV Infections

2020 ◽  
Vol 12 ◽  
Author(s):  
Sai Akilesh M ◽  
Ashish Wadhwani
Keyword(s):  
Drug Delivery ◽  
Viral Infections ◽  
Polymeric Nanoparticles ◽  
Volume Ratio ◽  
Fold Increase ◽  
Multi Drug Resistance ◽  
Health Crisis ◽  
Pharmaceutical Properties ◽  
Simplex Virus ◽  
The Impact

: Infectious diseases have been prevalent since many decades and viral pathogens have caused global health crisis and economic meltdown on a devastating scale. High occurrence of newer viral infections in the recent years, in spite of the progress achieved in the field of pharmaceutical sciences defines the critical need for newer and more effective antiviral therapies and diagnostics. The incidence of multi-drug resistance and adverse effects due to the prolonged use of anti-viral therapy is also a major concern. Nanotechnology offers a cutting edge platform for the development of novel compounds and formulations for biomedical applications. The unique properties of nano-based materials can be attributed to the multi-fold increase in the surface to volume ratio at the nano-scale, tunable surface properties of charge and chemical moieties. Idealistic pharmaceutical properties such as increased bioavailability and retention times, lower toxicity profiles, sustained release formulations, lower dosage forms and most importantly, targeted drug delivery can be achieved through the approach of nanotechnology. The extensively researched nano-based materials are metal and polymeric nanoparticles, dendrimers and micelles, nano-drug delivery vesicles, liposomes and lipid based nanoparticles. In this review article, the impact of nanotechnology on the treatment of Human Immunodeficiency Virus (HIV) and Herpes Simplex Virus (HSV) viral infections during the last decade are outlined.

The association between femoral neck shaft angle and degenerative disease of the hip in a cadaveric model

2021 ◽  
pp. 112070002110130
Author(s):  
Leigh-Anne Tu ◽  
Douglas S Weinberg ◽  
Raymond W Liu
Keyword(s):  
Femoral Head ◽  
Femoral Neck ◽  
Hip Osteoarthritis ◽  
Volume Ratio ◽  
Femoral Head Coverage ◽  
Neck Shaft Angle ◽  
Hip Arthritis ◽  
Femoral Version ◽  
Shaft Angle ◽  
The Impact

Background: While the influences of acetabular dysplasia and overcoverage on hip arthritis have been studied, the impact of femoral neck-shaft angle on hip arthritis is much more poorly understood. The purpose of this study is to determine if a relationship exists between neck shaft angle and the development of osteoarthritis, a better understanding of which would be useful to surgeons planning osteotomies about the hip. Methods: 533 cadaveric femora and acetabulae (1066 total) from the Hamann-Todd Osteological Collection (Cleveland, OH) were acquired. We measured true neck shaft angle using an AP photograph with the femoral neck parallel to the table. Femoral head volume to acetabular volume ratio, representing femoral head coverage, as well as femoral version were utilised. Correlation between neck shaft angle, femoral version, femoral head coverage and osteoarthritis were evaluated with multiple regression analysis. Results: The mean age and standard deviation was 56 ± 10 years. There were 64 females (12%) and 469 males. There were 380 Caucasians (71%) and 153 African-Americans. Mean femoral version was 11° ± 12° and mean true neck shaft angle was 127.7° ± 5.9° There was a strong correlation between age and arthritis (standardised beta 0.488, p < 0.001). There was a significant correlation between increasing true neck shaft angle and decreasing hip arthritis (standardised beta -0.024, p = 0.038). In the femoral head overcoverage subset, increasing true neck shaft angle was still significantly associated with decreasing hip arthritis (standardised beta −0.088, p = 0.018), although this relationship was not significant with femoral head undercoverage subset. Conclusions: With sufficient acetabular coverage, a relative increase in femoral neck shaft angle within the physiologic range is associated with decreased hip osteoarthritis. Clinical relevance: An understanding of the relationship between femoral neck shaft angle and hip osteoarthritis could be useful for surgeons planning pelvic or proximal femur osteotomies in children.

scholarly journals Virus-Like Particles Produced Using the Brome Mosaic Virus Recombinant Capsid Protein Expressed in a Bacterial System

2021 ◽  
Vol 22 (6) ◽  
pp. 3098
Author(s):  
Aleksander Strugała ◽  
Jakub Jagielski ◽  
Karol Kamel ◽  
Grzegorz Nowaczyk ◽  
Marcin Radom ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Mosaic Virus ◽  
Capsid Protein ◽  
Self Assembly ◽  
Environmental Changes ◽  
Expression System ◽  
Brome Mosaic Virus ◽  
Virus Like Particles ◽  
Assembly Principles ◽  
The Impact

Virus-like particles (VLPs), due to their nanoscale dimensions, presence of interior cavities, self-organization abilities and responsiveness to environmental changes, are of interest in the field of nanotechnology. Nevertheless, comprehensive knowledge of VLP self-assembly principles is incomplete. VLP formation is governed by two types of interactions: protein–cargo and protein–protein. These interactions can be modulated by the physicochemical properties of the surroundings. Here, we used brome mosaic virus (BMV) capsid protein produced in an E. coli expression system to study the impact of ionic strength, pH and encapsulated cargo on the assembly of VLPs and their features. We showed that empty VLP assembly strongly depends on pH whereas ionic strength of the buffer plays secondary but significant role. Comparison of VLPs containing tRNA and polystyrene sulfonic acid (PSS) revealed that the structured tRNA profoundly increases VLPs stability. We also designed and produced mutated BMV capsid proteins that formed VLPs showing altered diameters and stability compared to VLPs composed of unmodified proteins. We also observed that VLPs containing unstructured polyelectrolyte (PSS) adopt compact but not necessarily more stable structures. Thus, our methodology of VLP production allows for obtaining different VLP variants and their adjustment to the incorporated cargo.

scholarly journals Are Biogenic and Pyrogenic Mesoporous SiO2 Nanoparticles Safe for Normal Cells?

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1427
Author(s):  
Katarzyna Solarska-Ściuk ◽  
Kinga Adach ◽  
Sylwia Cyboran-Mikołajczyk ◽  
Dorota Bonarska-Kujawa ◽  
Agnieszka Rusak ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Silica Nanoparticles ◽  
Biological Effects ◽  
Mesoporous Silica Nanoparticles ◽  
Volume Ratio ◽  
Sio2 Nanoparticles ◽  
Amorphous Structure ◽  
Intracellular Ros ◽  
Materials Used ◽  
The Impact

Silicon dioxide, in the form of nanoparticles, possesses unique physicochemical properties (size, shape, and a large surface to volume ratio). Therefore, it is one of the most promising materials used in biomedicine. In this paper, we compare the biological effects of both mesoporous silica nanoparticles extracted from Urtica dioica L. and pyrogenic material. Both SEM and TEM investigations confirmed the size range of tested nanoparticles was between 6 and 20 nanometers and their amorphous structure. The cytotoxic activity of the compounds and intracellular ROS were determined in relation to cells HMEC-1 and erythrocytes. The cytotoxic effects of SiO2 NPs were determined after exposure to different concentrations and three periods of incubation. The same effects for endothelial cells were tested under the same range of concentrations but after 2 and 24 h of exposure to erythrocytes. The cell viability was measured using spectrophotometric and fluorimetric assays, and the impact of the nanoparticles on the level of intracellular ROS. The obtained results indicated that bioSiO2 NPs, present higher toxicity than pyrogenic NPs and have a higher influence on ROS production. Mesoporous silica nanoparticles show good hemocompatibility but after a 24 h incubation of erythrocytes with silica, the increase in hemolysis process, the decrease in osmotic resistance of red blood cells, and shape of erythrocytes changed were observed.

DNA-based self-assembly of nanostructures

2017 ◽  
Author(s):  
Joshua D. Carter ◽  
Chenxiang Lin ◽  
Yan Liu ◽  
Hao Yan ◽  
Thomas H. LaBean
Keyword(s):  
Self Assembly ◽  
Materials Science ◽  
Directed Assembly ◽  
Building Blocks ◽  
Hierarchical Assembly ◽  
Synthetic Dna ◽  
Nanoscale Manufacturing ◽  
Covalently Linked ◽  
Design Construction ◽  
Proteins And Peptides

This article examines the DNA-based self-assembly of nanostructures. It first reviews the development of DNA self-assembly and DNA-directed assembly, focusing on the main strategies and building blocks available in the modern molecular construction toolbox, including the design, construction, and analysis of nanostructures composed entirely of synthetic DNA, as well as origami nanostructures formed from a mixture of synthetic and biological DNA. In particular, it considers the stepwise covalent synthesis of DNA nanomaterials, unmediated assembly of DNA nanomaterials, hierarchical assembly, nucleated assembly, and algorithmic assembly. It then discusses DNA-directed assembly of heteromaterials such as proteins and peptides, gold nanoparticles, and multicomponent nanostructures. It also describes the use of complementary DNA cohesion as 'smart glue' for bringing together covalently linked functional groups, biomolecules, and nanomaterials. Finally, it evaluates the potential future of DNA-based self-assembly for nanoscale manufacturing for applications in medicine, electronics, photonics, and materials science.

Zeolates: A Coordination Chemistry View of Metal-Ligand Bonding in Intrazeolite MOCVD Type Precursors and Semiconductor Nanoclusters

1992 ◽  
Vol 277 ◽  
Author(s):  
Geoffrey A. Ozin ◽  
Carol L. Bowes ◽  
Mark R. Steele
Keyword(s):  
Self Assembly ◽  
Materials Science ◽  
Zeolite Y ◽  
Chemical Vapour ◽  
Internal Surface ◽  
Building Blocks ◽  
Structural Features ◽  
Organic Chemical ◽  
Wide Range ◽  
Shape Selective

ABSTRACTVarious MOCVD (metal-organic chemical vapour deposition) type precursors and their self-assembled semiconductor nanocluster products [1] have been investigated in zeolite Y hosts. From analysis of in situ observations (FTIR, UV-vis reflectance, Mössbauer, MAS-NMR) of the reaction sequences and structural features of the precursors and products (EXAFS and Rietveld refinement of powder XRD data) the zeolite is viewed as providing a macrospheroidal, multidendate coordination environment towards encapsulated guests. By thinking about the α- and β-cages of the zeolite Y host effectively as a zeolate ligand composed of interconnected aluminosilicate “crown ether-like” building blocks, the materials chemist is able to better understand and exploit the reactivity and coordination properties of the zeolite internal surface for the anchoring and self-assembly of a wide range of encapsulated guests. This approach helps with the design of synthetic strategies for creating novel guest-host inclusion compounds having possible applications in areas of materials science such as nonlinear optics, quantum electronics, and size/shape selective catalysis.

Sign in / Sign up

Export Citation Format

Share Document