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Sosa EM, Moure MM. Mechanical Characterization of Synthetic Gels for Creation of Surrogate Hands Subjected to Low-Velocity Impacts. Gels 2022; 8:gels8090559. [PMID: 36135273 PMCID: PMC9498611 DOI: 10.3390/gels8090559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 08/18/2022] [Accepted: 08/31/2022] [Indexed: 11/24/2022] Open
Abstract
The development of human body simulators that can be used as surrogates for testing protective devices and measures requires selecting synthetic materials with mechanical properties closely representative of the human tissues under consideration. For impact tests, gelatinous materials are often used to represent the soft tissues as a whole without distinguishing layers such as skin, fat, or muscles. This research focuses on the mechanical characterization of medical-grade synthetic gels that can be implemented to represent the soft tissues of the hand. Six grades of commercially available gels are selected for quasi-static hardness and firmness tests as well as for controlled low-velocity impact tests, which are not routinely conducted by gel manufacturers and require additional considerations such as energy level and specimen sizes relevant to the specific application. Specimens subject to impacts represent the hand thicknesses at the fingers, knuckles, and mid-metacarpal regions. Two impact test configurations are considered: one with the gel specimens including a solid insert representing a bone and one without this insert. The impact behavior of the candidate gels is evaluated by the coefficient of restitution, the energy loss percentage, and the peak reaction force at the time of impact. The resulting values are compared with similar indicators reported for experiments with cadaveric hands. Relatively softer gels, characterized by Shore OOO hardness in the range of 32.6 ± 0.9 to 34.4 ± 2.0, closely matched the impact behavior of cadaveric specimens. These results show that softer gels would be the most suitable gels to represent soft tissues in the creation of surrogate hands that can be used for extensive impact testing, thus, minimizing the need for cadaveric specimens.
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Affiliation(s)
- Eduardo M. Sosa
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506, USA
- Correspondence:
| | - Marta M. Moure
- Aerospace Systems and Transport Research Group, Rey Juan Carlos University, 28942 Fuenlabrada, Madrid, Spain
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Chen Y, Ding JL, Babaiasl M, Yang F, Swensen JP. Characterization and modeling of a thermoplastic elastomer tissue simulant under uniaxial compression loading for a wide range of strain rates. J Mech Behav Biomed Mater 2022; 131:105218. [DOI: 10.1016/j.jmbbm.2022.105218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 03/04/2022] [Accepted: 04/02/2022] [Indexed: 11/16/2022]
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Svendsen MBS, Ghulam QM, Zielinski AH, Lachenmeier C, Eiberg JP. Validation of an assessment tool for estimation of abdominal aortic aneurysm compression in diagnostic ultrasound. ULTRASONICS 2021; 116:106484. [PMID: 34102524 DOI: 10.1016/j.ultras.2021.106484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2020] [Revised: 03/26/2021] [Accepted: 05/27/2021] [Indexed: 06/12/2023]
Abstract
The study investigated ultrasound (US) transducer push, tantamount to applied transducer pressure, during abdominal aortic aneurysm (AAA) US scanning in a simulated non-clinical setup. During an assessment of maximal AAA diameter on a three-dimensional print-based AAA phantom, US transducer push varied as much as 2000% (range: 0.52-12.45 kPa) amongst 16 experienced sonographers. The mean transducer push was 5.54 ± 3.91 kPa (CV = 0.71). Deformation of a standardized gel-pad allowed for transducer push calculation based on US images; Young's modulus of the gel-pad was estimated to 44,26 N/m2. The method is theoretically validated in a safe and non-clinical environment. Future investigations with the aim of clinical validation of the gel-pad principle on AAA patients are suggested, including the objectification of the magnitude of an eventual transducer push-related error during US AAA diameter measurement.
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Affiliation(s)
| | - Qasam Mohammed Ghulam
- Department of Vascular Surgery, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark.
| | - Alexander Hakon Zielinski
- Department of Vascular Surgery, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark; Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Christian Lachenmeier
- Copenhagen Academy for Medical Education and Simulation (CAMES), Teilum, Blegdamsvej 9, 2100 Copenhagen, Denmark
| | - Jonas Peter Eiberg
- Copenhagen Academy for Medical Education and Simulation (CAMES), Teilum, Blegdamsvej 9, 2100 Copenhagen, Denmark; Department of Vascular Surgery, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark; Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
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Mineart KP, Hong C, Rankin LA. Decoupling of Mechanical and Transport Properties in Organogels via Solvent Variation. Gels 2021; 7:gels7020061. [PMID: 34064043 PMCID: PMC8162343 DOI: 10.3390/gels7020061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 05/18/2021] [Indexed: 11/22/2022] Open
Abstract
Organogels have recently been considered as materials for transdermal drug delivery media, wherein their transport and mechanical properties are among the most important considerations. Transport through organogels has only recently been investigated and findings highlight an inextricable link between gels’ transport and mechanical properties based upon the formulated polymer concentration. Here, organogels composed of styrenic triblock copolymer and different aliphatic mineral oils, each with a unique dynamic viscosity, are characterized in terms of their quasi-static uniaxial mechanical behavior and the internal diffusion of two unique solute penetrants. Mechanical testing results indicate that variation of mineral oil viscosity does not affect gel mechanical behavior. This likely stems from negligible changes in the interactions between mineral oils and the block copolymer, which leads to consistent crosslinked network structure and chain entanglement (at a fixed polymer concentration). Conversely, results from diffusion experiments highlight that two penetrants—oleic acid (OA) and aggregated aerosol-OT (AOT)—diffuse through gels at a rate inversely proportional to mineral oil viscosity. The inverse dependence is theoretically supported by the hydrodynamic model of solute diffusion through gels. Collectively, our results show that organogel solvent variation can be used as a design parameter to tailor solute transport through gels while maintaining fixed mechanical properties.
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Luo S, Wen Y, Li J. Experimental investigation on the characteristics of temporary cavity in BABT with 9 mm projectiles. Forensic Sci Int 2021; 323:110772. [PMID: 33872919 DOI: 10.1016/j.forsciint.2021.110772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 03/20/2021] [Accepted: 03/23/2021] [Indexed: 10/21/2022]
Abstract
Temporary cavity, one physical phenomenon in BABT reflects the dynamic response of biological tissues and is used to evaluate the trauma. To clarify the characteristics of cavity evolution during 9 mm Luger penetration, we obtain the deformation profiles by using an experimental method with a high-speed camera and thereby visualize the cavity formation and development. According to the dynamic impact experiments at the velocity from 220 to 420 m/s, the temporary cavity profile can be approximately regarded as a semi-ellipsoid. The maximum depth increases as a quadratic function of velocity. Additionally, the maximum volume of the temporary cavity is attained significantly after the maximum depth. The change rate of cavity volume in the expansion stage is larger than that in the contraction stage.
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Affiliation(s)
- Shaomin Luo
- School of Aerospace Engineering, Guizhou Institute of Technology, Guiyang 550003, Guizhou, China.
| | - Yaoke Wen
- School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu, China.
| | - Juan Li
- School of Materials and Metallurgical Engineering, Guizhou Institute of Technology, Guiyang 550003, Guizhou, China.
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Luo K, Subhash G, Spearot DE. On shockwave propagation and attenuation in poly(ethylene glycol) diacrylate hydrogels. J Mech Behav Biomed Mater 2021; 118:104423. [PMID: 33752092 DOI: 10.1016/j.jmbbm.2021.104423] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 01/13/2021] [Accepted: 02/21/2021] [Indexed: 10/22/2022]
Abstract
An analytical model is developed to predict shockwave propagation and attenuation in hydrogels by combining the classical method of shock characteristics and a solution for the shock front structure. To guide the development of the model, molecular dynamics (MD) simulations are performed. Specifically, a one-dimensional shock pulse in poly(ethylene glycol) diacrylate (PEGDA) hydrogels is simulated with the nonequilibrium MD method. The role of polymer concentration on the shock response is evaluated by constructing hydrogels with 20, 35, and 50 wt% PEGDA concentrations in an idealized crosslinked network. Steady-state pressure-density and shock-particle velocity relationships are established using the Murnaghan equation of state. Shock front structure is characterized by a power-law equation that relates the shock front thickness with shock pressure. These results are used as critical input for the shock propagation and attenuation model. The model is then evaluated via comparison with the classical method of characteristics. It shows significant improvement in accuracy and successfully captures salient features of shockwave attenuation, including the shock pressure amplitude, the velocities of the shock and release waves, and the attenuation timeline. Hydrogels with higher polymer concentrations exhibit a shorter attenuation time at all particle velocities studied. This behavior is attributed to differences in bulk properties and shock front structure in hydrogels with different polymer/water concentrations.
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Affiliation(s)
- Ke Luo
- Department of Materials Science & Engineering, University of Florida, USA
| | - Ghatu Subhash
- Department of Mechanical & Aerospace Engineering, University of Florida, USA
| | - Douglas E Spearot
- Department of Mechanical & Aerospace Engineering, University of Florida, USA.
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Coget Y, Demarty Y, Rusinek A. Characterization of the Mechanical Behavior of a Lead Alloy, from Quasi-Static to Dynamic Loading for a Wide Range of Temperatures. MATERIALS 2020; 13:ma13102357. [PMID: 32443908 PMCID: PMC7287887 DOI: 10.3390/ma13102357] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 05/14/2020] [Accepted: 05/15/2020] [Indexed: 11/23/2022]
Abstract
The current needs in terms of ballistic protection for armed forces require an almost constant improvement in performance to face the constantly evolving threats and scenarios. Ballistic tests are conventionally carried out in order to assess and validate the levels of protection. The challenge is to be able to set up a digital protocol and only carry out final validation tests. Indeed, the advantage of digital simulation lies in the possibility of being able to evaluate a wide variety of configurations. In order to obtain reliable results, it is necessary to use sufficiently precise material behavior models to transcribe the phenomena observed during the impact. Our study focuses on the behavior of a small caliber ammunition with a ductile core impacting personal protection. More particularly on the mechanical behavior of the lead alloy core. Thus, compression tests have been carried out on a wide range of deformation rates, from quasi-static behavior to dynamic regime, at different temperatures. The study in dynamic conditions was carried out using split Hopkinson pressure bars. Due to the material properties, the experimental device had to be adapted in order to optimize the propagation of the waves allowing to measure signals (elastic waves). These tests demonstrate the dependency of the stress with strain rate and temperature. Dynamic restoration and recrystallization phenomena, characteristic of a material deformed in its hot working area, have also been identified. The associated oscillations due to Pochhammer–Chree effect, observable on the stress–strain curves, constitute the major problem for the implementation of behavioral models. Finally, a constitutive model sensitive to strain rate and temperature is investigated for ballistic purposes.
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Affiliation(s)
- Yann Coget
- French-German research institute of Saint-Louis, 5 rue du Général Cassagnou, 68300 Saint-Louis, France;
- Laboratory of Microstructure Studies and Mechanics of Materials, UMR-CNRS 7239, Lorraine University, 7 rue Félix Savart, BP 15082, 57073 Metz, France
| | - Yaël Demarty
- French-German research institute of Saint-Louis, 5 rue du Général Cassagnou, 68300 Saint-Louis, France;
- Correspondence: (Y.D.); (A.R.)
| | - Alexis Rusinek
- Laboratory of Microstructure Studies and Mechanics of Materials, UMR-CNRS 7239, Lorraine University, 7 rue Félix Savart, BP 15082, 57073 Metz, France
- Correspondence: (Y.D.); (A.R.)
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Bracq A, Delille R, Maréchal C, Bourel B, Roth S, Mauzac O. Rib fractures prediction method for kinetic energy projectile impact: from blunt ballistic experiments on SEBS gel to impact modeling on a human torso FE model. Forensic Sci Int 2019; 297:177-183. [DOI: 10.1016/j.forsciint.2019.02.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2017] [Revised: 10/11/2018] [Accepted: 02/04/2019] [Indexed: 10/27/2022]
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Mishra S, Badani Prado RM, Lacy TE, Kundu S. Investigation of failure behavior of a thermoplastic elastomer gel. SOFT MATTER 2018; 14:7958-7969. [PMID: 30113614 DOI: 10.1039/c8sm01397g] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Gels are increasingly being used in many applications, and it is important to understand how these gels fail subjected to mechanical deformation. Here, we investigate the failure behavior of a thermoplastic elastomer gel (TPEG) consisting of poly(styrene)-poly(isoprene)-poly(styrene) in mineral oil, in tensile mode, under constant stress, and in fracture tests, where the fracture initiates from a predefined crack. In these gels, the poly(styrene) endblocks associate to form spherical aggregates, as captured using SAXS. Shear-rheology experiments indicate that the poly(isoprene) midblocks connecting these aggregates are loosely entangled. The relaxation behavior of these gels has been captured by time-temperature superposition of frequency sweep data and stress-relaxation experiments. The relaxation process in these gels involves endblock pullout from the aggregates and subsequent relaxation of the chains. An unfavorable enthalpic interaction between the endblock and mineral oil results in a significantly large relaxation time. These gels display rate dependent mechanical properties, likely due to the midblock entanglements. Fracture and creep failure tests provide insights into the gel failure mechanism. Creep experiments indicate that these gels fail by a thermally activated process. Fracture experiments capture the energy release rate as a function of crack-tip velocity. The critical energy release rate is estimated by incorporating the friction force the polystyrene chains are subjected to, as those are pulled out of aggregates, and the enthalpic cost to overcome unfavorable interaction between poly(styrene) and mineral oil. Our results provide further insights to the failure behavior of the self-assembled TPEGs.
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Affiliation(s)
- Satish Mishra
- Dave C. Swalm School of Chemical Engineering, Mississippi State University, MS State, MS 39762, USA.
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