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Quince Z, Alonso-Caneiro D, Read SA, Collins MJ. Static compression optical coherence elastography to measure the mechanical properties of soft contact lenses. BIOMEDICAL OPTICS EXPRESS 2021; 12:1821-1833. [PMID: 33996200 PMCID: PMC8086445 DOI: 10.1364/boe.419344] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 02/12/2021] [Accepted: 02/23/2021] [Indexed: 06/12/2023]
Abstract
In this study, a novel method was developed for estimating the elastic modulus (Young's modulus) of soft contact lens materials using static compression optical coherence elastography. Using a commercially available spectral domain optical coherence tomography instrument, an experimental setup was developed to image a soft contact lens sample before and during compression with a known applied force, from which the lens material's mechanical properties can be derived. A semi-automatic segmentation method using graph-search theory and dynamic processing was used to trace the lens boundaries and to determine key structural changes within the images. To validate the method, five soft contact lens materials with a range of known elastic moduli and water contents were tested. The proposed method was successful in estimating the Young's modulus in the five different soft contact lens materials. It was demonstrated that the method provides highly repeatable measurements, with an intraclass correlation coefficient of >95%. The Young's modulus results were compared to published manufacturer data with no significant difference for four out of the five materials (p > 0.05). These results demonstrate that a static compression optical coherence tomography method can reliably measure the elastic modulus of soft contact lenses. This provides a methodology that can be used to explore in vitro contact lens mechanical properties, but more importantly, may also be extended to study the mechanical characteristics of in vivo or ex vivo tissue, provided that they can be imaged using OCT.
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Ishihara K, Fukazawa K, Sharma V, Liang S, Shows A, Dunbar DC, Zheng Y, Ge J, Zhang S, Hong Y, Shi X, Wu JY. Antifouling Silicone Hydrogel Contact Lenses with a Bioinspired 2-Methacryloyloxyethyl Phosphorylcholine Polymer Surface. ACS OMEGA 2021; 6:7058-7067. [PMID: 33748619 PMCID: PMC7970573 DOI: 10.1021/acsomega.0c06327] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 02/03/2021] [Indexed: 05/24/2023]
Abstract
Inspired by the cell membrane surface as well as the ocular tissue, a novel and clinically applicable antifouling silicone hydrogel contact lens material was developed. The unique chemical and biological features on the surface on a silicone hydrogel base substrate were achieved by a cross-linked polymer layer composed of 2-methacryloyloxyethyl phosphorylcholine (MPC), which was considered important for optimal on-eye performance. The effects of the polymer layer on adsorption of biomolecules, such as lipid and proteins, and adhesion of cells and bacteria were evaluated and compared with several conventional silicone hydrogel contact lens materials. The MPC polymer layer provided significant resistance to lipid deposition as visually demonstrated by the three-dimensional confocal images of whole contact lenses. Also, fibroblast cell adhesion was decreased to a 1% level compared with that on the conventional silicone hydrogel contact lenses. The movement of the cells on the surface of the MPC polymer-modified lens material was greater compared with other silicone hydrogel contact lenses indicating that lubrication of the contact lenses on ocular tissue might be improved. The superior hydrophilic nature of the MPC polymer layer provides improved surface properties compared to the underlying silicone hydrogel base substrate.
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Affiliation(s)
- Kazuhiko Ishihara
- Department
of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Kyoko Fukazawa
- Department
of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Vinay Sharma
- Alcon
Vision LLC, Fort Worth, Texas 76134, United States
| | - Shuang Liang
- Alcon
Vision LLC, Fort Worth, Texas 76134, United States
| | - Amanda Shows
- Alcon
Vision LLC, Fort Worth, Texas 76134, United States
| | | | - Yang Zheng
- Alcon
Vision LLC, Duluth, Georgia 30097, United
States
| | - Junhao Ge
- Alcon
Vision LLC, Duluth, Georgia 30097, United
States
| | - Steve Zhang
- Alcon
Vision LLC, Duluth, Georgia 30097, United
States
| | - Ye Hong
- Alcon
Vision LLC, Duluth, Georgia 30097, United
States
| | - Xinfeng Shi
- Alcon
Vision LLC, Fort Worth, Texas 76134, United States
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3
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Schulte MF, Bochenek S, Brugnoni M, Scotti A, Mourran A, Richtering W. Stiffness Tomography of Ultra-Soft Nanogels by Atomic Force Microscopy. Angew Chem Int Ed Engl 2021; 60:2280-2287. [PMID: 33459462 PMCID: PMC7898630 DOI: 10.1002/anie.202011615] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Indexed: 01/02/2023]
Abstract
The softness of nanohydrogels results in unique properties and recently attracted tremendous interest due to the multi-functionalization of interfaces. Herein, we study extremely soft temperature-sensitive ultra-low cross-linked (ULC) nanogels adsorbed to the solid/water interface by atomic force microscopy (AFM). The ultra-soft nanogels seem to disappear in classical imaging modes since a sharp tip fully penetrates these porous networks with very low forces in the range of steric interactions (ca. 100 pN). However, the detailed evaluation of Force Volume mode measurements allows us to resolve their overall shape and at the same time their internal structure in all three dimensions. The nanogels exhibit an extraordinary disk-like and entirely homogeneous but extremely soft structure-even softer than polymer brushes. Moreover, the temperature-sensitive nanogels can be switched on demand between the ultra-soft and a very stiff state.
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Affiliation(s)
| | - Steffen Bochenek
- Institute of Physical ChemistryRWTH Aachen UniversityLandoltweg 252056AachenGermany
| | - Monia Brugnoni
- Institute of Physical ChemistryRWTH Aachen UniversityLandoltweg 252056AachenGermany
| | - Andrea Scotti
- Institute of Physical ChemistryRWTH Aachen UniversityLandoltweg 252056AachenGermany
| | - Ahmed Mourran
- DWI—Leibniz Institute for Interactive MaterialsForckenbeckstr. 5052056AachenGermany
| | - Walter Richtering
- Institute of Physical ChemistryRWTH Aachen UniversityLandoltweg 252056AachenGermany
- DWI—Leibniz Institute for Interactive MaterialsForckenbeckstr. 5052056AachenGermany
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Shi X, Cantu-Crouch D, Sharma V, Pruitt J, Yao G, Fukazawa K, Wu JY, Ishihara K. Surface characterization of a silicone hydrogel contact lens having bioinspired 2-methacryloyloxyethyl phosphorylcholine polymer layer in hydrated state. Colloids Surf B Biointerfaces 2021; 199:111539. [PMID: 33387797 DOI: 10.1016/j.colsurfb.2020.111539] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 12/14/2020] [Accepted: 12/15/2020] [Indexed: 01/08/2023]
Abstract
A silicone hydrogel contact lens material, with a unique chemical and physical structure has been designed for long-term ocular performance. Enhancement of this silicone hydrogel contact lens material was achieved through surface modification using a cross-linkable bioinspired 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer, which creates a soft surface gel layer on the silicone hydrogel base material. The surface properties of this MPC polymer-modified lens were characterized under hydrated condition revealing, inter alia, its unique polymer structure, excellent hydrophilicity, lubricity, and flexibility. Analysis of the MPC polymer layer in a hydrated state was performed using a combination of a high-resolution environmental scanning electron microscopy and atomic force microscopy. Compared to the silicone hydrogel base material, this surface had a higher captive bubble contact angle, which corresponds to higher hydrophilicity of the surface. In addition, the hydrated MPC polymer layer exhibited an extremely soft surface and reduced the coefficient of friction by more than 80 %. These characteristics were attributed to the hydration state of the MPC polymer layer on the surface of the silicone hydrogel base material. Also, interaction force of protein deposition was lowered on the surface. Such superior surface properties are anticipated to contribute to excellent ocular performance.
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Affiliation(s)
- Xinfeng Shi
- Alcon Vision, LLC, Fort Worth, TX, 76134, USA
| | | | | | | | - George Yao
- Alcon Vision, LLC, Duluth, GA, 30097, USA
| | - Kyoko Fukazawa
- Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | | | - Kazuhiko Ishihara
- Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
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5
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Schulte MF, Bochenek S, Brugnoni M, Scotti A, Mourran A, Richtering W. Stiffness Tomography of Ultra‐Soft Nanogels by Atomic Force Microscopy. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202011615] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- M. Friederike Schulte
- Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52056 Aachen Germany
| | - Steffen Bochenek
- Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52056 Aachen Germany
| | - Monia Brugnoni
- Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52056 Aachen Germany
| | - Andrea Scotti
- Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52056 Aachen Germany
| | - Ahmed Mourran
- DWI—Leibniz Institute for Interactive Materials Forckenbeckstr. 50 52056 Aachen Germany
| | - Walter Richtering
- Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52056 Aachen Germany
- DWI—Leibniz Institute for Interactive Materials Forckenbeckstr. 50 52056 Aachen Germany
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6
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Burgener K, Bhamla MS. A polymer-based technique to remove pollutants from soft contact lenses. Cont Lens Anterior Eye 2020; 44:101335. [PMID: 32444249 DOI: 10.1016/j.clae.2020.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 05/07/2020] [Accepted: 05/10/2020] [Indexed: 11/18/2022]
Abstract
PURPOSE To demonstrate an alternative to the rinse and rub (RR) method for cleaning pollutants from the exterior surface of soft contact lenses. This proposed technique is termed Polymer on Polymer Pollutant Removal (PoPPR), which utilizes the elastic properties of polydimethylsiloxane (PDMS) to physically remove contaminants from contact lens surfaces through non-adhesive unpeeling. METHODS Three different ratios of setting agent to polymer PDMS (1:30, 1:40, and 1:50) were evaluated using the PoPPR method against the control method of RR with a commercial multi-purpose lens cleaning solution. Three simulated pollutants of different sizes: pollen (25-40 μm), microbeads (1-5 μm), and nanoparticles (5-10 nm), were used to test the effectiveness of both cleaning methods. The fraction of pollutants removed from each contact lens was recorded and evaluated for significance. RESULTS PDMS 1:40 was found to be the optimal ratio for lens cleaning using the PoPPR method. For larger particles (>10 μm), no difference was observed between conventional RR and proposed PoPPR method (p > 0.05). However, the new PoPPR technique was significantly better at removing small PM2.5 particles (<2.5 μm) compared to the RR method, specifically for microbeads (p = 0.006) and nanoparticles (p < 0.001). CONCLUSION This proof-of-concept work demonstrates that the PoPPR method of cleaning contact lenses is as effective as the conventional cleaning method for larger particles such as pollen. The PoPPR method is more effective at removing extremely fine particulate pollutants, including microplastics and nanoparticles. This method offers a potentially more efficient cleaning protocol that could enhance the safety, health, and comfort of contact lens users, especially those living in regions with significant air pollution.
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Affiliation(s)
- Katherine Burgener
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, United States
| | - M Saad Bhamla
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, United States.
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7
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Kim S, Korolovych VF, Muhlbauer RL, Tsukruk VV. 3D‐printed
polymer packing structures: Uniformity of morphology and mechanical properties via microprocessing conditions. J Appl Polym Sci 2020. [DOI: 10.1002/app.49381] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Sunghan Kim
- School of Mechanical EngineeringChung‐Ang University Seoul South Korea
| | - Volodymyr F. Korolovych
- School of Materials Science and EngineeringGeorgia Institute of Technology Atlanta Georgia USA
| | | | - Vladimir V. Tsukruk
- School of Materials Science and EngineeringGeorgia Institute of Technology Atlanta Georgia USA
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8
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Mutlu Z, Shams Es‐haghi S, Cakmak M. Recent Trends in Advanced Contact Lenses. Adv Healthc Mater 2019; 8:e1801390. [PMID: 30938941 DOI: 10.1002/adhm.201801390] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 02/28/2019] [Indexed: 12/28/2022]
Abstract
Exploiting contact lenses for ocular drug delivery is an emerging field in the area of biomedical engineering and advanced healthcare materials. Despite all the research conducted in this area, still, new technologies are in their early stages of the development, and more work must be done in terms of clinical trials to commercialize these technologies. A great challenge in using contact lenses for drug delivery is to achieve a prolonged drug release profile within the therapeutic range for various eye-related problems and diseases. In general, desired release kinetics to avoid the initial burst release is the zero-order kinetics within the therapeutic range. This review highlights the new technologies developed to achieve efficient and extended drug delivery. It also provides an overview of the materials and methods for fabrication of contact lenses and their mechanical and optical properties.
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Affiliation(s)
- Zeynep Mutlu
- Birck Nanotechnology CenterPurdue University West Lafayette IN 47907‐2057 USA
- School of Materials EngineeringPurdue University West Lafayette IN 47907‐2045 USA
| | - Siamak Shams Es‐haghi
- Birck Nanotechnology CenterPurdue University West Lafayette IN 47907‐2057 USA
- School of Materials EngineeringPurdue University West Lafayette IN 47907‐2045 USA
| | - Mukerrem Cakmak
- Birck Nanotechnology CenterPurdue University West Lafayette IN 47907‐2057 USA
- School of Materials EngineeringPurdue University West Lafayette IN 47907‐2045 USA
- School of Mechanical EngineeringPurdue University West Lafayette IN 47907‐2088 USA
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Abstract
This review discusses the important concept of cotton fiber friction at both the macro- and nanoscale. First, the technological importance of fiber friction and its role in fiber breakage during fiber processing is discussed. Next, previous studies on frictional properties of cotton fibers are reviewed and different experimental procedures to measure friction between fibers or against another surface are evaluated. Friction models developed to explain friction process during various experimental procedures are considered and their limitations are discussed. Since interpretation of friction processes at the macroscale can be challenging (mainly due to difficulties in analyzing the multiple asperities in contact), a separate section is devoted to surveying studies on the emerging field of single-asperity friction experiments with atomic force microscope (AFM). Special attention is given to studies on nanoscale frictional characteristics of rough viscoelastic surfaces (e.g., plant cuticular biopolymers and cotton fibers). Due to the close relationship between friction and adhesion hysteresis at the nanoscale, adhesion studies with AFM on viscoelastic surfaces are also reviewed. Lastly, recommendations are made for future research in the field of frictional properties of cotton fibers.
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10
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Schulte MF, Scotti A, Gelissen APH, Richtering W, Mourran A. Probing the Internal Heterogeneity of Responsive Microgels Adsorbed to an Interface by a Sharp SFM Tip: Comparing Core-Shell and Hollow Microgels. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:4150-4158. [PMID: 29509428 DOI: 10.1021/acs.langmuir.7b03811] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Microgels composed of thermoresponsive polymer poly( N-isopropylacrylamide) (PNIPAM) are interfacial active. Their adsorption leads to deformation, causing conformational changes that have profound effects on the macroscopic properties of these films. Yet, methods to quantitatively probe the local density are lacking. We introduced scanning force microscopy (SFM) to quantitatively probe the internal structure of microgels physically adsorbed on a solid (SiO2)/water interface. Using a sharp SFM tip, we investigated the two types of microgels: (i) core-shell microgels featuring a hard silica core and a PNIPAM shell and (ii) hollow microgels obtained by dissolution of the silica core. Thus, both systems have the same polymer network as the peripheral structure but a distinctly different internal structure, that is, a rigid core versus a void. By evaluating the force-distance curves, the force profile during insertion of the tip into the polymer network enables to determine a depth-dependent contact resistance, which closely correlates with the density profiles determined in solution by small-angle neutron scattering. We found that the cavity of the swollen hollow microgels is still present when adsorbed to the solid substrate. Remarkably, while currently used techniques such as colloidal probe or reflectometry only provide an average of the z-profile, the methodology introduced herein actually probes the real three-dimensional density profile, which is ultimately important to understand the macroscopic behavior of microgel films. This will bridge the gap between the colloidal probe experiments that deform the microgel globally and the insertion in which the disturbance is located near the tip.
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Affiliation(s)
- M Friederike Schulte
- Institute of Physical Chemistry , RWTH Aachen University , Landoltweg 2 , 52056 Aachen , Germany
- DWI-Leibniz Institute for Interactive Materials , Forckenbeckstr. 50 , 52056 Aachen , Germany
| | - Andrea Scotti
- Institute of Physical Chemistry , RWTH Aachen University , Landoltweg 2 , 52056 Aachen , Germany
| | - Arjan P H Gelissen
- Institute of Physical Chemistry , RWTH Aachen University , Landoltweg 2 , 52056 Aachen , Germany
| | - Walter Richtering
- Institute of Physical Chemistry , RWTH Aachen University , Landoltweg 2 , 52056 Aachen , Germany
- DWI-Leibniz Institute for Interactive Materials , Forckenbeckstr. 50 , 52056 Aachen , Germany
| | - Ahmed Mourran
- DWI-Leibniz Institute for Interactive Materials , Forckenbeckstr. 50 , 52056 Aachen , Germany
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11
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Maza E, von Bilderling C, Cortez ML, Díaz G, Bianchi M, Pietrasanta LI, Giussi JM, Azzaroni O. Layer-by-Layer Assembled Microgels Can Combine Conflicting Properties: Switchable Stiffness and Wettability without Affecting Permeability. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:3711-3719. [PMID: 29480725 DOI: 10.1021/acs.langmuir.8b00047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Responsive interfacial architectures of practical interest commonly require the combination of conflicting properties in terms of their demand upon material structure. Switchable stiffness, wettability, and permeability, key features for tissue engineering applications, are in fact known to be exclusively interdependent. Here, we present a nanoarchitectonic approach that decouples these divergent properties by the use of thermoresponsive microgels as building blocks for the construction of three-dimensional arrays of interconnected pores. Layer-by-layer assembled poly( N-isopropylacrylamide- co-methacrylic acid) microgel films were found to exhibit an increase in hydrophobicity, stiffness, and adhesion properties upon switching the temperature from below to above the lower critical solution temperature, whereas the permeability of redox probes through the film remained unchanged. Our findings indicate that the switch in hydrophilicity and nanomechanical properties undergone by the microgels does not compromise the porosity of the film, thus allowing the free diffusion of redox probes through the polymer-free volume of the submicrometer pores. This novel approach for decoupling conflicting properties provides a strategic route for creating tailorable scaffolds with unforeseen functionalities.
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Affiliation(s)
- Eliana Maza
- Instituto de Investigaciones Fisicoquímicas teóricas y Aplicadas (INIFTA) , Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional de La Plata (UNLP) , Diagonal 113 y 64 s/n , 1900 La Plata , Buenos Aires , Argentina
| | - Catalina von Bilderling
- Instituto de Investigaciones Fisicoquímicas teóricas y Aplicadas (INIFTA) , Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional de La Plata (UNLP) , Diagonal 113 y 64 s/n , 1900 La Plata , Buenos Aires , Argentina
| | - M Lorena Cortez
- Instituto de Investigaciones Fisicoquímicas teóricas y Aplicadas (INIFTA) , Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional de La Plata (UNLP) , Diagonal 113 y 64 s/n , 1900 La Plata , Buenos Aires , Argentina
| | - Gisela Díaz
- Instituto de Investigaciones Fisicoquímicas teóricas y Aplicadas (INIFTA) , Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional de La Plata (UNLP) , Diagonal 113 y 64 s/n , 1900 La Plata , Buenos Aires , Argentina
| | | | | | - Juan M Giussi
- Instituto de Investigaciones Fisicoquímicas teóricas y Aplicadas (INIFTA) , Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional de La Plata (UNLP) , Diagonal 113 y 64 s/n , 1900 La Plata , Buenos Aires , Argentina
| | - Omar Azzaroni
- Instituto de Investigaciones Fisicoquímicas teóricas y Aplicadas (INIFTA) , Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional de La Plata (UNLP) , Diagonal 113 y 64 s/n , 1900 La Plata , Buenos Aires , Argentina
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MacManus DB, Gilchrist MD, Murphy JG. An empirical measure of nonlinear strain for soft tissue indentation. ROYAL SOCIETY OPEN SCIENCE 2017; 4:170894. [PMID: 29291082 PMCID: PMC5717656 DOI: 10.1098/rsos.170894] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 09/26/2017] [Indexed: 05/09/2023]
Abstract
Indentation is a primary tool in the investigation of the mechanical properties of very soft tissue such as the brain. However, the usual material characterization protocols are not applicable because the resulting deformation is inhomogeneous, with even the identification of the amount of strain ambiguous and uncertain. Focusing on spherical indentation only, a standard is needed to quantify the amount of strain in terms of the probe radius and displacement so that different indentation experiments can be compared and contrasted. It is shown here that the minimum axial value of the Eulerian logarithmic strain tensor has many desirable properties of such a standard, such as invariance under the choice of material model, and experimental conditions for a given probe displacement. The disadvantage of this measure is that sophisticated finite element techniques need to be used in its determination. An empirical relation is obtained between this strain and the probe radius and displacement to circumvent this problem, and it is shown that this relationship is an excellent predictor of the strain measure. Two essential features of this empirical measure for nonlinear strains are that the exact strain measure for the linear theory is recovered on restriction to infinitesimal deformations and that the simulations use models based on reliable and accurate indentation data obtained from freshly harvested murine brains using a bespoke micro-indentation device.
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Affiliation(s)
- D. B. MacManus
- Department of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin 4, Ireland
- Author for correspondence: D. B. MacManus e-mail:
| | - M. D. Gilchrist
- Department of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin 4, Ireland
| | - J. G. Murphy
- Department of Mechanical Engineering, Dublin City University, Glasnevin, Dublin 9, Ireland
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13
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Bhamra TS, Tighe BJ. Mechanical properties of contact lenses: The contribution of measurement techniques and clinical feedback to 50 years of materials development. Cont Lens Anterior Eye 2016; 40:70-81. [PMID: 27884616 DOI: 10.1016/j.clae.2016.11.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 11/09/2016] [Accepted: 11/11/2016] [Indexed: 10/20/2022]
Abstract
PURPOSE This review summarises the way in which mechanical property measurements combined with clinical perception have influenced the last half century of materials evolution in contact lens development. METHODS Literature concerning the use of in-vitro testing in assessment of the mechanical behaviour of contact lenses, and the mutual deformation of the lens material and ocular tissue was examined. Tensile measurements of historic and available hydrogel lenses have been collected, in addition to manufacturer-generated figures for the moduli of commercial silicone hydrogel lenses. RESULTS The three conventional modes of mechanical property testing; compression, tension and shear each represent different perspective in understanding the mutual interaction of the cornea and the contact lens. Tensile testing provides a measure of modulus, together with tensile strength and elongation to break, which all relate to handling and durability. Studies under compression also measure modulus and in particular indicate elastic response to eyelid load. Studies under shear conditions enable dynamic mechanical behaviour of the material to be assessed and the elastic and viscous components of modulus to be determined. These different methods of measurement have contributed to the interpretation of lens behaviour in the ocular environment. An amalgamated frequency distribution of tensile moduli for historic and currently available contact lens materials reveals the modal range to be 0.3-0.6MPa. CONCLUSION Mechanical property measurements of lens materials have enabled calibration of an important aspect of their ocular interaction. This together with clinical feedback has influenced development of new lens materials and assisted clinical rationalisation of in-eye behaviour of different lenses.
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Affiliation(s)
- Tarnveer Singh Bhamra
- Biomaterials Research Unit, Chemical Engineering and Applied Chemistry, Aston University, Aston Triangle, Birmingham, B4 7ET, UK.
| | - Brian J Tighe
- Biomaterials Research Unit, Chemical Engineering and Applied Chemistry, Aston University, Aston Triangle, Birmingham, B4 7ET, UK
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14
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15
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Fontenier B, Hault-Dubrulle A, Drazetic P, Fontaine C, Naceur H. On the mechanical characterization and modeling of polymer gel brain substitute under dynamic rotational loading. J Mech Behav Biomed Mater 2016; 63:44-55. [PMID: 27341290 DOI: 10.1016/j.jmbbm.2016.06.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 06/03/2016] [Accepted: 06/06/2016] [Indexed: 10/21/2022]
Abstract
The use of highly sensitive soft materials has become increasingly apparent in the last few years in numerous industrial fields, due to their viscous and damping nature. Unfortunately these materials remain difficult to characterize using conventional techniques, mainly because of the very low internal forces supported by these materials especially under high strain-rates of deformation. The aim of this work is to investigate the dynamic response of a polymer gel brain analog material under specific rotational-impact experiments. The selected polymer gel commercially known as Sylgard 527 has been studied using a specific procedure for its experimental characterization and numerical modeling. At first an indentation experiment was conducted at several loading rates to study the strain rate sensitivity of the Sylgard 527 gel. During the unloading several relaxation tests were performed after indentation, to assess the viscous behavior of the material. A specific numerical procedure based on moving least square approximation and response surface method was then performed to determine adequate robust material parameters of the Sylgard 527 gel. A sensitivity analysis was assessed to confirm the robustness of the obtained material parameters. For the validation of the obtained material model, a second experiment was conducted using a dynamic rotational loading apparatus. It consists of a metallic cylindrical cup filled with the polymer gel and subjected to an eccentric transient rotational impact. Complete kinematics of the cup and the large strains induced in the Sylgard 527 gel, have been recorded at several patterns by means of optical measurement. The whole apparatus was modeled by the Finite Element Method using explicit dynamic time integration available within Ls-dyna(®) software. Comparison between the physical and the numerical models of the Sylgard 527 gel behavior under rotational choc shows excellent agreements.
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Affiliation(s)
- B Fontenier
- Laboratory LAMIH UMR 8201 CNRS, University of Valenciennes, 59313 Valenciennes, France.
| | - A Hault-Dubrulle
- Laboratory LAMIH UMR 8201 CNRS, University of Valenciennes, 59313 Valenciennes, France
| | - P Drazetic
- Laboratory LAMIH UMR 8201 CNRS, University of Valenciennes, 59313 Valenciennes, France
| | - C Fontaine
- Laboratory of Anatomy, University of Lille 2, 59000 Lille, France
| | - H Naceur
- Laboratory LAMIH UMR 8201 CNRS, University of Valenciennes, 59313 Valenciennes, France
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Megevand B, Pruvost S, Lins LC, Livi S, Gérard JF, Duchet-Rumeau J. Probing nanomechanical properties with AFM to understand the structure and behavior of polymer blends compatibilized with ionic liquids. RSC Adv 2016. [DOI: 10.1039/c6ra18492h] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The PeakForce QNM AFM mode was used to investigate the nanoscale mechanical properties of poly(butylene-adipate-co-terephthalate)/poly(lactic acid) (PBAT/PLA) blends successfully compatibilized with phosphonium-based ionic liquids (ILs).
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Affiliation(s)
- Benjamin Megevand
- Université de Lyon
- INSA Lyon
- UMR CNRS 5223
- IMP Ingénierie des Matériaux Polymères
- F-69621 Villeurbanne
| | - Sébastien Pruvost
- Université de Lyon
- INSA Lyon
- UMR CNRS 5223
- IMP Ingénierie des Matériaux Polymères
- F-69621 Villeurbanne
| | - Luanda C. Lins
- Université de Lyon
- INSA Lyon
- UMR CNRS 5223
- IMP Ingénierie des Matériaux Polymères
- F-69621 Villeurbanne
| | - Sébastien Livi
- Université de Lyon
- INSA Lyon
- UMR CNRS 5223
- IMP Ingénierie des Matériaux Polymères
- F-69621 Villeurbanne
| | - Jean-François Gérard
- Université de Lyon
- INSA Lyon
- UMR CNRS 5223
- IMP Ingénierie des Matériaux Polymères
- F-69621 Villeurbanne
| | - Jannick Duchet-Rumeau
- Université de Lyon
- INSA Lyon
- UMR CNRS 5223
- IMP Ingénierie des Matériaux Polymères
- F-69621 Villeurbanne
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