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Viswanath Managuli, Sitikantha Roy
A new asymptotically correct contact model has been developed for conical tip based AFM nanoindentation. This new model provides both elastic and non-specific adhesion properties of cells and soft gels by taking sample thickness at the point of indentation and its depth of indentation into consideration. The bottom substrate effect is the most common source of error in the study of "AFM force maps" of the cellular sample. The present model incorporates an asymptotically correct correction term as a function of depth of indentation to eliminate the substrate effect in the analysis...
July 17, 2017: Journal of Biomechanical Engineering
Z L Zhou, X X Sun, J Ma, M H Tong, S K Y To, A S T Wong, A H W Ngan
Recent studies have indicated that the nanoindentation measured stiffness of carcinoma adherent cells is in general lower than normal cells, thus suggesting that cell stiffness may serve as a bio-marker for carcinoma. However, the proper establishment of such a conclusion would require biophysical understanding of the underlying mechanism of the cell stiffness. In this work, we compared the elastic moduli of the actin cytoskeletons of Hey A8 ovarian carcinoma cells with and without metastasis (HM and NM), as measured by 2D atomic force microscopy (AFM) with low-depth nanoindentation via a rate-jump method...
July 5, 2017: Journal of Biomechanics
Erqiang Liu, Gesheng Xiao, Wufei Jia, Xuefeng Shu, Xuexia Yang, Yulei Wang
To study the tetragonal-to-monoclinic (T-M) phase transformation behavior under different strain rates and indentation depths, nanoindentation tests were performed on stabilized zirconia ceramics with Continuous Stiffness Measurements. The results indicate decreased phase transformation velocities at both lower and higher strain rates, but increased velocity under medium strain rate during loading. The phase transformation process is sensitive to Ṗ/P but the final volume fractions are almost identical (45%)...
July 5, 2017: Journal of the Mechanical Behavior of Biomedical Materials
Prashant Chandrasekaran, Basak Doyran, Qing Li, Biao Han, Till E Bechtold, Eiki Koyama, X Lucas Lu, Lin Han
This study aims to quantify the biomechanical properties of murine temporomandibular joint (TMJ) articular disc and condyle cartilage using AFM-nanoindentation. For skeletally mature, 3-month old mice, the surface of condyle cartilage was found to be significantly stiffer (306±84kPa, mean±95% CI) than those of the superior (85±23kPa) and inferior (45±12kPa) sides of the articular disc. On the disc surface, significant heterogeneity was also detected across multiple anatomical sites, with the posterior end being the stiffest and central region being the softest...
June 27, 2017: Journal of Biomechanics
Tao Fu, Xianghe Peng, Cheng Huang, Henggao Xiang, Shayuan Weng, Zhongchang Wang, Ning Hu
Twin boundaries (TBs) have been observed in and introduced into nonmetallic materials in recent years, which brought new concepts for the design of new structural materials. However, the roles of TB on the mechanical properties and strengthening/softening of transition metal nitrides remain unclear. To investigate the TB effects and the in-plane anisotropy, nanoindentations on VN (111) films with and without TB were simulated with molecular dynamics, in which a cylindrical indenter was used, and its longitudinal axis were assigned along <112> and <110>, respectively...
July 6, 2017: Scientific Reports
Shijing Sun, Furkan H Isikgor, Zeyu Deng, Fengxia Wei, Gregor Kieslich, Paul D Bristowe, Jianyong Ouyang, Anthony K Cheetham
The mechanical properties of formamidinium lead halide perovskites (FAPbX3, X = Br or I) grown by inverse temperature crystallization have been studied by nanoindentation. The measured Young's moduli (9.7 - 12.3 GPa) and hardnesses (0.36 - 0.45 GPa) indicate good mechanical flexibility and ductility. The effects of hydrogen bonding were evaluated by performing ab initio molecular dynamics on both formamidinium and methylammonium perovskites and calculating radial distribution functions. The structural and chemical factors influencing these properties are discussed by comparison with corresponding values in the literature for other hybrid perovskites, including double perovskites...
June 30, 2017: ChemSusChem
Na-Ri Kang, Young-Cheon Kim, Hansol Jeon, Seong Keun Kim, Jae-Il Jang, Heung Nam Han, Ju-Young Kim
We fabricate nanotubular ZnO with wall thickness of 45, 92, 123 nm using nanoporous gold (np-Au) with ligament diameter at necks of 1.43 μm as sacrificial template. Through micro-tensile and micro-compressive testing of nanotubular ZnO structures, we find that the exponent m in [Formula: see text], where [Formula: see text] is the relative strength and [Formula: see text] is the relative density, for tension is 1.09 and for compression is 0.63. Both exponents are lower than the value of 1.5 in the Gibson-Ashby model that describes the relation between relative strength and relative density where the strength of constituent material is independent of external size, which indicates that strength of constituent ZnO increases as wall thickness decreases...
June 28, 2017: Scientific Reports
Malgorzata Kopycinska-Mueller, Martin Barth, Martin Kuettner, Bernd Koehler
We confirmed the occurrence of phase transformations in an AFM silicon tip during loading and unloading experiments performed on a polycrystalline Ti sample. The influence of the phase transformations on the effective mechanical and electrical properties of the tip was observed with the help of load-unload curves measured simultaneously for the tip-sample contact stiffness k* and the effective electrical resistance of the system Reff. We used the atomic force acoustic microscopy (AFAM) method to determine the values of k*...
June 26, 2017: Nanotechnology
Orlaith Brennan, Joseph Sweeney, Brian O'Meara, Amro Widaa, Franck Bonnier, Hugh J Byrne, Denise M O'Gorman, Fergal J O'Brien
Calcium supplements are used as an aid in the prevention of osteopenia and osteoporosis and also for the treatment of patients when used along with medication. Many of these supplements are calcium carbonate based. This study compared a calcium-rich, marine multi-mineral complex (Aquamin) to calcium carbonate in an ovariectomised rat model of osteoporosis in order to assess Aquamin's efficacy in preventing the onset of bone loss. Animals were randomly assigned to either non-ovariectomy control (Control), ovariectomy (OVX) plus calcium carbonate, ovariectomy plus Aquamin or ovariectomy plus Aquamin delay where Aquamin treatment started 8 weeks post OVX...
June 24, 2017: Calcified Tissue International
K Saeki, Y-C Chien, G Nonomura, A F Chin, S Habelitz, L B Gower, S J Marshall, G W Marshall
OBJECTIVES: Acetate and lactate are important cariogenic acids produced by oral bacteria. They produced different residual dentin structures in artificial lesions of similar depth. We evaluated if such lesions responded in the same way to a polymer-induced-liquid-precursor (PILP) remineralization. DESIGN: Dentin blocks obtained from human third molars, divided into 6 groups (n=3). Blocks were demineralized with acetate (66h) or lactate (168h) buffer at pH 5.0 to create 140μm target lesion depths...
June 15, 2017: Archives of Oral Biology
Zhengdi He, Lingling Chen, Xuejuan Hu, Yasushi Shimada, Masayuki Otsuki, Junji Tagami, Shuangchen Ruan
The purpose of this study was to evaluate the chemical and mechanical modifications in subsurface dentin layer after Er: YAG (Erbium-Yttrium Aluminium Garnet) laser irradiation, as the guidance of new dental restorative materials specific for laser irradiated dentin. MATERIALS AND METHODS: Dentin disks obtained from extracted human molars were prepared and exposed to a single pulse Er:YAG laser irradiation at 80mJ/pulse. After laser irradiation the mechanical and chemical characteristics of intertubular dentin in subsurface layer were studied using nanoindentation tester and micro-Raman spectromy (μ-RS)...
June 3, 2017: Journal of the Mechanical Behavior of Biomedical Materials
Ippei Hamanaka, Misa Iwamoto, Lippo V J Lassila, Pekka K Vallittu, Yutaka Takahashi
Objective This study investigated the wear resistance of injection-molded thermoplastic denture base resins using nanoindentation instrument. Materials and methods Six injection-molded thermoplastic denture base resins (two polyamides, two polyesters, one polycarbonate, one polymethylmethacrylate [PMMA]) and a PMMA conventional heat-polymerized denture-based polymer control were tested. Elastic modulus, hardness, wear depth, and roughness were calculated using a nanoindentation instrument. Results Elastic modulus and hardness of the injection-molded thermoplastic denture base resins were significantly lower than those of the PMMA conventional heat-polymerized denture-based polymer...
December 2016: Acta Biomaterialia Odontologica Scandinavica
Tooba Shoaib, Prathima C Nalam, Yichen He, Yuting Chen, Rosa M Espinosa-Marzal
Recognizing the limitations of solid-supported lipid bilayers to reproduce the behavior of cell membranes, including bendability, transmembrane protein inclusion, and virus entry, this study describes a novel biomimetic system for cell membranes with the potential to overcome these and other limitations. The developed strategy utilizes a hydrogel with tunable mechanical behavior that resembles those of living cells as the soft support for the phospholipid bilayer, while a polyelectrolyte multilayer film serves as an intermediate layer to facilitate the self-assembly of the lipid bilayer on the soft cushion...
July 5, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Fang Wang, S S Jyothirmayee Aravind, Hao Wu, Joseph Forys, Venkat Venkataraman, Kandalam Ramanujachary, Xiao Hu
Green graphene materials prepared by photoreduction of graphite oxide were first time blended with aqueous-based silk fibroin proteins to improve the mechanical and thermal properties of silk biomaterials, and their nanocomposite interaction mechanism was illustrated. Powder X-ray diffraction (XRD) analysis confirmed the complete exfoliation of graphite oxide to graphene in presence of focused pulses of solar radiation. By varying the concentration of graphene (0.1wt% to 10wt%), a series of free standing graphene-silk films were prepared and were systematically characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and nanoindentation measurements...
October 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
J Mora-Macías, A Pajares, P Miranda, J Domínguez, E Reina-Romo
Nanoindentation has been used successfully in the determination of the mechanical properties of bone. Its application in fracture healing provides information on the evolution of material properties of the woven bone during regeneration process. However, this technique has not been applied in assessing the mechanical properties of woven bone during distraction osteogenesis. Therefore, the aim of this work is to evaluate the spatial and temporal variations of the elastic modulus of the woven bone generated during the bone transport process...
June 1, 2017: Journal of the Mechanical Behavior of Biomedical Materials
Matthew Faulkner, Jorge Rodriguez-Ramos, Gregory F Dykes, Siân V Owen, Selene Casella, Deborah M Simpson, Robert J Beynon, Lu-Ning Liu
Carboxysomes are proteinaceous organelles that play essential roles in enhancing carbon fixation in cyanobacteria and some proteobacteria. These self-assembling organelles encapsulate Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) and carbonic anhydrase using a protein shell structurally resembling an icosahedral viral capsid. The protein shell serves as a physical barrier to protect enzymes from the cytosol and a selectively permeable membrane to mediate transport of enzyme substrates and products...
June 15, 2017: Nanoscale
Biljana Janković, Tatjana Joksimović, Jernej Stare, Evgeniy Losev, Viktoriya Zemtsova, Stane Srčič, Elena Boldyreva
The nanomechanical properties of the α-, β-, and γ- conformational polymorphs of chlorpropamide were determined by the dynamic contact module continuous stiffness measurement at nanoindenter. The mechanical anisotropy of the α-polymorph was confirmed by indenting different faces, and its deformational behavior was assigned as ductile. Based on the nanoindentation results, the β and γ forms are moderately hard with plastic flow at contact points. The results revealed a correlation between Young's modulus and inter-planar interaction energy with regard to crystal orientation...
June 9, 2017: European Journal of Pharmaceutical Sciences
Christopher L Salinas, Enrique Escobar de Obaldia, Chanhue Jeong, Jessica Hernandez, Pablo Zavattieri, David Kisailus
Gastropods shells have evolved to resist the threat of increasingly stronger predators that smash, peal, and crush their shells. Their shells are most commonly constructed from a crossed lamellar microstructure, which consists of an exquisitely architected arrangement of aragonitic mineral and organic encompassing at least four orders of hierarchy. It is this careful control of mineral and organic placement within the entire crossed lamellar structure that yields a four-order of magnitude increase in fracture toughness versus abiotic aragonite...
May 31, 2017: Journal of the Mechanical Behavior of Biomedical Materials
Ping Hu, Shun Dong, Xinghong Zhang, Kaixuan Gui, Guiqing Chen, Ze Hu
Several-millimeter long SiC nanowires (NWs) with unique optical properties, excellent thermal stability and flexible nanomechanical properties were synthesized using a simple method with silicon and phenolic resin as the raw materials. The SiC NWs displayed special optical properties that were attributed to their large size and Al-doping. They displayed broad green emission at 527.8 nm (2.35 eV) and purple emission concentrated at 438.9 nm (2.83 eV), in contrast to the other results, and the synthesized SiC NWs could also remain relatively stable in air up to 1000 °C indicating excellent thermal stability...
June 7, 2017: Scientific Reports
Emily Callard Preedy, Stefano Perni, Polina Prokopovich
Bone cells are damaged by wear particles originating from total joint replacement implants. We investigated Mesenchymal stem cells (MSCs) nanomechanical properties when exposed to cobalt and titanium nanoparticles (resembling wear debris) of different sizes for up to 3days using AFM nanoindentation; along with flow-cytometry and MTT assay. The results demonstrated that cells exposed to increasing concentrations of nanoparticles had a lower value of elasticity and spring constant without significant effect on cell metabolic activity and viability but some morphological alteration (bleeping)...
May 10, 2017: Colloids and Surfaces. B, Biointerfaces
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