Biomimetic multilayer coatings deliver gentamicin and reduce implant-related osteomyelitis in rats

2019 ◽  
Vol 64 (4) ◽  
pp. 383-395
Author(s):  
Steffi Grohmann ◽  
Manuela Menne ◽  
Diana Hesse ◽  
Sabine Bischoff ◽  
René Schiffner ◽  
...  
Keyword(s):  
Orthopedic Surgery ◽  
Material Properties ◽  
Bulk Material ◽  
Local Delivery ◽  
Multilayer Coatings ◽  
Assembly Process ◽  
Polyelectrolyte Multilayer ◽  
Cytotoxic Effects ◽  
Joint Infections ◽  
Main Components

Abstract Implant-related infections like periprosthetic joint infections (PJI) are still a challenging issue in orthopedic surgery. In this study, we present a prophylactic anti-infective approach based on a local delivery of the antibiotic gentamicin. The local delivery is achieved via a nanoscale polyelectrolyte multilayer (PEM) coating that leaves the bulk material properties of the implant unaffected while tuning the surface properties. The main components of the coating, i.e. polypeptides and sulfated glycosaminoglycans (sGAG) render this coating both biomimetic (matrix mimetic) and biodegradable. We show how adaptions in the conditions of the multilayer assembly process and the antibiotic loading process affect the amount of delivered gentamicin. The highest concentration of gentamicin could be loaded into films composed of polypeptide poly-glutamic acid when the pH of the loading solution was acidic. The concentration of gentamicin on the surface could be tailored with the number of deposited PEM layers. The resulting coatings reveal a bacteriotoxic effect on Staphylococcus cells but show no signs of cytotoxic effects on MC3T3-E1 osteoblasts. Moreover, when multilayer-coated titanium rods were implanted into contaminated medullae of rat tibiae, a reduction in the development of implant-related osteomyelitis was observed. This reduction was more pronounced for the multifunctional, matrix-mimetic heparin-based coatings that only deliver lower amounts of gentamicin.

scholarly journals A methodology for hygrothermal modelling of imperfect masonry interfaces

2021 ◽  
pp. 174425912198938
Author(s):  
Michael Gutland ◽  
Scott Bucking ◽  
Mario Santana Quintero
Keyword(s):  
Boundary Conditions ◽  
Material Properties ◽  
Structural Integrity ◽  
Bulk Material ◽  
Weather Conditions ◽  
Masonry Wall ◽  
Two Dimensional ◽  
Liquid Transport ◽  
Imperfect Contact ◽  
Moisture Contents

Hygrothermal models are important tools for assessing the risk of moisture-related decay mechanisms which can compromise structural integrity, loss of architectural features and material. There are several sources of uncertainty when modelling masonry, related to material properties, boundary conditions, quality of construction and two-dimensional interactions between mortar and unit. This paper examines the uncertainty at the mortar-unit interface with imperfections such as hairline cracks or imperfect contact conditions. These imperfections will alter the rate of liquid transport into and out of the wall and impede the liquid transport between mortar and masonry unit. This means that the effective liquid transport of the wall system will be different then if only properties of the bulk material were modelled. A detailed methodology for modelling this interface as a fracture is presented including definition of material properties for the fracture. The modelling methodology considers the combined effect of both the interface resistance across the mortar-unit interface and increase liquid transport in parallel to the interface, and is generalisable to various combinations of materials, geometries and fracture apertures. Two-dimensional DELPHIN models of a clay brick/cement-mortar masonry wall were created to simulate this interaction. The models were exposed to different boundary conditions to simulate wetting, drying and natural cyclic weather conditions. The results of these simulations were compared to a baseline model where the fracture model was not included. The presence of fractures increased the rate of absorption in the wetting phase and an increased rate of desorption in the drying phase. Under cyclic conditions, the result was higher peak moisture contents after rain events compared to baseline and lower moisture contents after long periods of drying. This demonstrated that detailed modelling of imperfections at the mortar-unit interface can have a definitive influence on results and conclusions from hygrothermal simulations.

scholarly journals Most recent developments in electrospun magnetic nanofibers: A review

2020 ◽  
Vol 15 ◽  
pp. 155892501990084 ◽  
Author(s):  
Tomasz Blachowicz ◽  
Andrea Ehrmann
Keyword(s):  
Material Properties ◽  
Bulk Material ◽  
Basic Research ◽  
Diameter Ratio ◽  
Cell Manipulation ◽  
One Dimensional ◽  
Magnetic Structures ◽  
Recent Developments ◽  
Large Length ◽  
Magnetic Nanofibers

One-dimensional materials, such as nanowires, nanotubes, or nanofibers, have attracted more and more attention recently due to their unique physical properties. Their large length-to-diameter ratio creates anisotropic material properties which could not be reached in bulk material. Especially one-dimensional magnetic structures are of high interest since the strong shape anisotropy reveals new magnetization reversal modes and possible applications. One possibility to create magnetic nanofibers in a relatively simple way is offered by electrospinning them from polymer solutions or melts with incorporated magnetic nanoparticles. This review gives an overview of most recent methods of electrospinning magnetic nanofibers, measuring their properties as well as possible applications from basic research to single-cell manipulation to microwave absorption.

scholarly journals Rapidly Solidified Gas-Atomized Aluminum Alloys Compared with Conventionally Cast Counterparts: Implications for Cold Spray Materials Consolidation

Coatings ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1035
Author(s):  
Bryer C. Sousa ◽  
Caitlin Walde ◽  
Victor K. Champagne, Jr. ◽  
Aaron T. Nardi ◽  
Richard D. Sisson, Jr. ◽  
...  
Keyword(s):  
Cold Spray ◽  
Material Properties ◽  
In Silico ◽  
Bulk Material ◽  
Processing Parameters ◽  
Fine Tuning ◽  
Secondary Phases ◽  
Scanning Calorimetry ◽  
Rapidly Solidified ◽  
Conventionally Cast

In this work, three commercially available aluminum alloy systems (Al 2024, Al 6061, and Al 7075) were considered to explicitly capture the differences in material properties associated with a rapidly solidified, gas-atomized particulate feedstock as compared with their conventionally cast counterparts. Differences between the microstructural, thermodynamic, mechanical, and kinetic behaviors associated with gas-atomized and conventionally bulk counterparts have been tacitly assumed by the cold spray community. However, many researchers continue to utilize legacy properties from bulk materials when simulating particle impact phenomena in silico, for example. By way of recognizing the fact that bulk material properties may not serve as substitutes for gas-atomized powder property input parameters for cold spray process simulation and computation in silico, enhanced cold spray research and development will be more easily achieved. Therefore, understanding the feedstock powder characteristics for use in cold spray can lead to fine-tuning the properties of cold spray consolidations. Optical microscopy, scanning electron microscopy, nanoindentation, microhardness, differential scanning calorimetry, elemental analysis, and cooling rate calculations were utilized. This work confirms preliminary findings that powder alloys may not be treated the same way as their bulk counterparts in so far as the enactment of heat treatment processing parameters are concerned. Specifically, vast discrepancies were found in the grain size, secondary phases, and mechanical behavior between the powder and cast versions of each alloy.

MEMS Die Warpage During Curing of Die Attach Material

2015 ◽  
Author(s):  
Hohyung Lee ◽  
Ruiyang Liu ◽  
Seungbae Park ◽  
Xiaojie Xue
Keyword(s):  
Material Properties ◽  
Residual Strain ◽  
Critical Role ◽  
Measurement Data ◽  
Curing Process ◽  
Assembly Process ◽  
Structural Elements ◽  
Mems Sensor ◽  
Fea Model ◽  
Die Attach

Microelectromechanical system (MEMS) packages are vulnerable to stresses due to its functional structure. During the assembly process of the package, stresses stemming out of CTE mismatches of the structural elements and curing of the die attach material can cause warpage of the MEMS die [1]. Even though die attach material takes relatively small volumetric portion of the package, it plays a critical role in warpage of the die due to its location and sensitivity of a MEMS sensor. Most of virgin die attach adhesives are in a state of viscous liquid and, as it is cured the material properties such as modulus and CTE change. Accordingly, residual strain is cumulated on MEMS die after curing process and signal trim process is required. Therefore, the material properties changes depending on the curing profile is valuable information for assembly process of the MEMS package. To monitor the material properties changes and shrinkage during curing process, strain and modulus of a die attach material are measured in each curing step. Also, to investigate the material property change depending on the curing profile, two different curing profiles are used. Experimental data show that die attach materials are gradually cured after each thermal cycling, which cause the increment of the modulus and glass transition temperature (Tg) with shrinkage at elevated temperature. Using the measurement data, FEA model is built to predict the warpage of the MEMS die. In the FEA model, residual strain on MEMS die is calculated by inputting material properties of die attach in each curing step. Also, die warpage of the package during the curing process is monitored using an optical profiler for the validation of the simulation results.

Mechanical Response of Porous and Dense NiTi-TiC Composites

2004 ◽  
Vol 844 ◽  
Author(s):  
Douglas E. Burkes ◽  
Guglielmo Gottoli ◽  
John J. Moore ◽  
Reed A. Ayers
Keyword(s):  
Material Properties ◽  
Mechanical Response ◽  
Bulk Material ◽  
Processing Parameters ◽  
Ceramic Composites ◽  
Advanced Materials ◽  
Matrix Composites ◽  
Compression Tests ◽  
Commercial Applications ◽  
Micro Indentation

ABSTRACTThe Center for Commercial Applications of Combustion in Space (CCACS) at the Colorado School of Mines is currently using combustion synthesis to produce several advanced materials. These materials include ceramic, intermetallic, and metal-matrix composites in both porous and dense form. Currently, NiTi – TiC intermetallic ceramic composites are under investigation for use as a bone replacement material. The NiTi intermetallic has the potential to provide a surface that is capable of readily producing an oxide layer for corrosion resistance. The TiC ceramic has the potential to increase the hardness and wear resistance of the bulk material that can improve the performance lifetime of the implant. Processing parameters are critical to the production of the NiTi – TiC composite and will be discussed. These parameters can lead to the formation of substoichiometric TiC and nickel rich NiTi that changes the overall mechanical and material properties. In addition, the size of the TiC particles present within the bulk product varies with porosity. Both porous and dense samples have been mechanically analyzed employing micro-indentation techniques as well as compression tests in an attempt to characterize the mechanical response of these composites. The effects of the TiC particles, the formation of Ni3Ti intermetallic and the effects of porosity on the overall mechanical and material properties will be discussed.

Optimal Elastic Design of CFCs

2011 ◽  
Vol 488-489 ◽  
pp. 295-298 ◽  
Author(s):  
Galyna Stasiuk ◽  
Romana Piat ◽  
Yuriy Sinchuk
Keyword(s):  
Elastic Properties ◽  
Material Properties ◽  
Bulk Material ◽  
Carbon Composite ◽  
Bending Test ◽  
Three Point Bending ◽  
Design Variables ◽  
Tension And Compression ◽  
Elastic Design ◽  
Analytical Homogenization

The aim of the proposed studies is the development of the carbon/carbon composite with prescribed elastic properties. To achieve this, a microstructure optimisation problem for estimation of the microstructure with prescribed stiffness is formulated. The design variables of the posed problem are the local fibers distribution and porosity. The volume fractions of the fibers and pores in the whole microstructure are fixed. Material properties of the local microstructure of the composite are calculated using virtual models. Semi-analytical homogenization procedures were used for the development of these models. Modeling results are compared with elastic properties obtained experimentally by tension and compression test and ultrasonic studies of the bulk material. Approach to design microstructure for three point bending test is proposed.

scholarly journals Morphology and Structure of Compacted Coated Powders Studied by SEM and TEM

2008 ◽  
Vol 14 (S3) ◽  
pp. 31-34
Author(s):  
F. Simões ◽  
B. Trindade
Keyword(s):  
High Temperatures ◽  
Material Properties ◽  
Room Temperature ◽  
Coating Layer ◽  
Bulk Material ◽  
Hot Isostatic Pressing ◽  
Al Alloys ◽  
Morphology And Structure ◽  
High Plastic ◽  
Oxidation And Corrosion

The interest in titanium based intermetallics, such as Ti-Al alloys, for high temperatures applications has been increased in recent years mainly due to their high plastic deformation resistance, chemistry stability (oxidation and corrosion resistance) and creep and fatigue resistance at high temperatures. However, the industrial application of Ti-Al intermetallics is very limited so far, due to the lack of ductility and fracture toughness at room temperature with associated processing difficulties. To overcome this problem and to improve mechanical properties of Ti-Al intermetallics, a powder mixture with atomic composition of Ti52Al48 was synthesized by mechanical alloying (MA) and subsequently coated with a ductile element (aluminium), by d.c. magnetron sputtering. Later, in order to obtain a compacted material, as final step, the coated MA'ed powders were submitted to hot isostatic pressing (HIP), giving rise to a bulk material. The aim of the current work is to understand the influence of coating layer in mechanical alloyed (MA'ed) powders and the influence in bulk material properties.

scholarly journals Solving the problem of classification of material properties using a neural network

2021 ◽  
Vol 2131 (3) ◽  
pp. 032084
Author(s):  
N E Babushkina ◽  
A A Lyapin
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Recurrent Neural Network ◽  
Material Properties ◽  
Practical Significance ◽  
Experimental Measurements ◽  
Statistical Parameters ◽  
The Neural Network ◽  
Main Components

Abstract The article sets the task of classifying various materials and determining their belonging to a specified group using a recurrent neural network. The practical significance of the article is to obtain the results of the neural network, confirming the possibility of classifying materials by the hardness parameter using a neural network. As part of the study, a number of experimental measurements were carried out. The structure of the neural network and its main components are described. The statistical parameters of the experimental data are estimated.

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