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El-Azab SA, Zhang C, Jiang S, Vyatskikh AL, Valdevit L, Lavernia EJ, Schoenung JM. In situ observation of melt pool evolution in ultrasonic vibration-assisted directed energy deposition. Sci Rep 2023; 13:17705. [PMID: 37848463 PMCID: PMC10582076 DOI: 10.1038/s41598-023-44108-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Accepted: 10/03/2023] [Indexed: 10/19/2023] Open
Abstract
The presence of defects, such as pores, in materials processed using additive manufacturing represents a challenge during the manufacturing of many engineering components. Recently, ultrasonic vibration-assisted (UV-A) directed energy deposition (DED) has been shown to reduce porosity, promote grain refinement, and enhance mechanical performance in metal components. Whereas it is evident that the formation of such microstructural features is affected by the melt pool behavior, the specific mechanisms by which ultrasonic vibration (UV) influences the melt pool remain elusive. In the present investigation, UV was applied in situ to DED of 316L stainless steel single tracks and bulk parts. For the first time, high-speed video imaging and thermal imaging were implemented in situ to quantitatively correlate the application of UV to melt pool evolution in DED. Extensive imaging data were coupled with in-depth microstructural characterization to develop a statistically robust dataset describing the observed phenomena. Our findings show that UV increases the melt pool peak temperature and dimensions, while improving the wettability of injected particles with the melt pool surface and reducing particle residence time. Near the substrate, we observe that UV results in a 92% decrease in porosity, and a 54% decrease in dendritic arm spacing. The effect of UV on the melt pool is caused by the combined mechanisms of acoustic cavitation, ultrasound absorption, and acoustic streaming. Through in situ imaging we demonstrate quantitatively that these phenomena, acting simultaneously, effectively diminish with increasing build height and size due to acoustic attenuation, consequently decreasing the positive effect of implementing UV-A DED. Thus, this research provides valuable insight into the value of in situ imaging, as well as the effects of UV on DED melt pool dynamics, the stochastic interactions between the melt pool and incoming powder particles, and the limitations of build geometry on the UV-A DED technique.
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Affiliation(s)
- Salma A El-Azab
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA
| | - Cheng Zhang
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA
| | - Sen Jiang
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA
| | - Aleksandra L Vyatskikh
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA
| | - Lorenzo Valdevit
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA
| | - Enrique J Lavernia
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA
| | - Julie M Schoenung
- Department of Materials Science and Engineering, University of California, 716 Engineering Tower, Irvine, CA, 92697, USA.
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2
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Bauer J, Sala-Casanovas M, Amiri M, Valdevit L. Nanoarchitected metal/ceramic interpenetrating phase composites. Sci Adv 2022; 8:eabo3080. [PMID: 35977008 PMCID: PMC9385151 DOI: 10.1126/sciadv.abo3080] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 07/06/2022] [Indexed: 06/03/2023]
Abstract
Architected metals and ceramics with nanoscale cellular designs, e.g., nanolattices, are currently subject of extensive investigation. By harnessing extreme material size effects, nanolattices demonstrated classically inaccessible properties at low density, with exceptional potential for superior lightweight materials. This study expands the concept of nanoarchitecture to dense metal/ceramic composites, presenting co-continuous architectures of three-dimensional printed pyrolytic carbon shell reinforcements and electrodeposited nickel matrices. We demonstrate ductile compressive deformability with elongated ultrahigh strength plateaus, resulting in an extremely high combination of compressive strength and strain energy absorption. Simultaneously, property-to-weight ratios outperform those of lightweight nanolattices. Superior to cellular nanoarchitectures, interpenetrating nanocomposites may combine multiple size-dependent characteristics, whether mechanical or functional, which are radically antagonistic in existing materials. This provides a pathway toward previously unobtainable multifunctionality, extending far beyond lightweight structure applications.
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Affiliation(s)
- Jens Bauer
- Materials Science and Engineering Department, University of California, Irvine, Irvine, CA 92697, USA
| | - Martí Sala-Casanovas
- Mechanical and Aerospace Engineering Department, University of California, Irvine, Irvine, CA 92697, USA
| | - Mahsa Amiri
- Materials Science and Engineering Department, University of California, Irvine, Irvine, CA 92697, USA
| | - Lorenzo Valdevit
- Materials Science and Engineering Department, University of California, Irvine, Irvine, CA 92697, USA
- Mechanical and Aerospace Engineering Department, University of California, Irvine, Irvine, CA 92697, USA
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3
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Thiraux R, Dupuy AD, Lei T, Rupert TJ, Mohraz A, Valdevit L. Damage tolerance in additively manufactured ceramic architected materials. Ann Ital Chir 2022. [DOI: 10.1016/j.jeurceramsoc.2022.05.059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Bauer J, Kraus JA, Crook C, Rimoli JJ, Valdevit L. Tensegrity Metamaterials: Toward Failure-Resistant Engineering Systems through Delocalized Deformation. Adv Mater 2021; 33:e2005647. [PMID: 33543809 DOI: 10.1002/adma.202005647] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 12/01/2020] [Indexed: 06/12/2023]
Abstract
Failure of materials and structures is inherently linked to localized mechanisms, from shear banding in metals, to crack propagation in ceramics and collapse of space-trusses after buckling of individual struts. In lightweight structures, localized deformation causes catastrophic failure, limiting their application to small strain regimes. To ensure robustness under real-world nonlinear loading scenarios, overdesigned linear-elastic constructions are adopted. Here, the concept of delocalized deformation as a pathway to failure-resistant structures and materials is introduced. Space-tileable tensegrity metamaterials achieving delocalized deformation via the discontinuity of their compression members are presented. Unprecedented failure resistance is shown, with up to 25-fold enhancement in deformability and orders of magnitude increased energy absorption capability without failure over same-strength state-of-the-art lattice architectures. This study provides important groundwork for design of superior engineering systems, from reusable impact protection systems to adaptive load-bearing structures.
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Affiliation(s)
- Jens Bauer
- Mechanical and Aerospace Engineering Department, University of California, Irvine, Irvine, CA, 92697, USA
| | - Julie A Kraus
- School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Cameron Crook
- Materials Science and Engineering Department, University of California, Irvine, Irvine, CA, 92697, USA
| | - Julian J Rimoli
- School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Lorenzo Valdevit
- Mechanical and Aerospace Engineering Department, University of California, Irvine, Irvine, CA, 92697, USA
- Materials Science and Engineering Department, University of California, Irvine, Irvine, CA, 92697, USA
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5
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Bauer J, Izard AG, Zhang Y, Baldacchini T, Valdevit L. Thermal post-curing as an efficient strategy to eliminate process parameter sensitivity in the mechanical properties of two-photon polymerized materials. Opt Express 2020; 28:20362-20371. [PMID: 32680097 DOI: 10.1364/oe.395986] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 06/10/2020] [Indexed: 06/11/2023]
Abstract
Two-photon polymerization direct laser writing (TPP-DLW) is one of the most versatile technologies to additively manufacture complex parts with nanoscale resolution. However, the wide range of mechanical properties that results from the chosen combination of multiple process parameters imposes an obstacle to its widespread use. Here we introduce a thermal post-curing route as an effective and simple method to increase the mechanical properties of acrylate-based TPP-DLW-derived parts by 20-250% and to largely eliminate the characteristic coupling of processing parameters, material properties and part functionality. We identify the underlying mechanism of the property enhancement as a self-initiated thermal curing reaction, which robustly facilitates the high property reproducibility that is essential for any application of TPP-DLW.
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Crook C, Bauer J, Guell Izard A, Santos de Oliveira C, Martins de Souza E Silva J, Berger JB, Valdevit L. Plate-nanolattices at the theoretical limit of stiffness and strength. Nat Commun 2020; 11:1579. [PMID: 32221283 PMCID: PMC7101344 DOI: 10.1038/s41467-020-15434-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 03/09/2020] [Indexed: 11/29/2022] Open
Abstract
Though beam-based lattices have dominated mechanical metamaterials for the past two decades, low structural efficiency limits their performance to fractions of the Hashin-Shtrikman and Suquet upper bounds, i.e. the theoretical stiffness and strength limits of any isotropic cellular topology, respectively. While plate-based designs are predicted to reach the upper bounds, experimental verification has remained elusive due to significant manufacturing challenges. Here, we present a new class of nanolattices, constructed from closed-cell plate-architectures. Carbon plate-nanolattices are fabricated via two-photon lithography and pyrolysis and shown to reach the Hashin-Shtrikman and Suquet upper bounds, via in situ mechanical compression, nano-computed tomography and micro-Raman spectroscopy. Demonstrating specific strengths surpassing those of bulk diamond and average performance improvements up to 639% over the best beam-nanolattices, this study provides detailed experimental evidence of plate architectures as a superior mechanical metamaterial topology. Plate-lattices are predicted to reach the upper bounds of strength and stiffness compared to traditional beam-lattices, but they are difficult to manufacture. Here, the authors use two-photon polymerization 3D-printing and pyrolysis to make carbon plate-nanolattices which reach those theoretical bounds, making them up to 639% stronger than beam-nanolattices.
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Affiliation(s)
- Cameron Crook
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA
| | - Jens Bauer
- Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA, USA.
| | - Anna Guell Izard
- Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA, USA
| | | | | | - Jonathan B Berger
- Nama Development, LLC, Goleta, CA, USA.,Materials Department, University of California, Santa Barbara, CA, USA
| | - Lorenzo Valdevit
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA.,Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA, USA
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Guell Izard A, Bauer J, Crook C, Turlo V, Valdevit L. Ultrahigh Energy Absorption Multifunctional Spinodal Nanoarchitectures. Small 2019; 15:e1903834. [PMID: 31531942 DOI: 10.1002/smll.201903834] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 08/31/2019] [Indexed: 06/10/2023]
Abstract
Nanolattices are promoted as next-generation multifunctional high-performance materials, but their mechanical response is limited to extreme strength yet brittleness, or extreme deformability but low strength and stiffness. Ideal impact protection systems require high-stress plateaus over long deformation ranges to maximize energy absorption. Here, glassy carbon nanospinodals, i.e., nanoarchitectures with spinodal shell topology, combining ultrahigh energy absorption and exceptional strength and stiffness at low weight are presented. Noncatastrophic deformation up to 80% strain, and energy absorption up to one order of magnitude higher than for other nano-, micro-, macro-architectures and solids, and state-of-the-art impact protection structures are shown. At the same time, the strength and stiffness are on par with the most advanced yet brittle nanolattices, demonstrating true multifunctionality. Finite element simulations show that optimized shell thickness-to-curvature-radius ratios suppress catastrophic failure by impeding propagation of dangerously oriented cracks. In contrast to most micro- and nano-architected materials, spinodal architectures may be easily manufacturable on an industrial scale, and may become the next generation of superior cellular materials for structural applications.
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Affiliation(s)
- Anna Guell Izard
- Department of Mechanical and Aerospace Engineering, University of California, Irvine, Irvine, CA, 92697, USA
| | - Jens Bauer
- Department of Mechanical and Aerospace Engineering, University of California, Irvine, Irvine, CA, 92697, USA
| | - Cameron Crook
- Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA, 92697, USA
| | - Vladyslav Turlo
- Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA, 92697, USA
| | - Lorenzo Valdevit
- Department of Mechanical and Aerospace Engineering, University of California, Irvine, Irvine, CA, 92697, USA
- Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA, 92697, USA
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8
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Garcia AE, Wang CS, Sanderson RN, McDevitt KM, Zhang Y, Valdevit L, Mumm DR, Mohraz A, Ragan R. Scalable synthesis of gyroid-inspired freestanding three-dimensional graphene architectures. Nanoscale Adv 2019; 1:3870-3882. [PMID: 36132116 PMCID: PMC9418730 DOI: 10.1039/c9na00358d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 09/16/2019] [Indexed: 05/26/2023]
Abstract
Three-dimensional porous architectures of graphene are desirable for energy storage, catalysis, and sensing applications. Yet it has proven challenging to devise scalable methods capable of producing co-continuous architectures and well-defined, uniform pore and ligament sizes at length scales relevant to applications. This is further complicated by processing temperatures necessary for high quality graphene. Here, bicontinuous interfacially jammed emulsion gels (bijels) are formed and processed into sacrificial porous Ni scaffolds for chemical vapor deposition to produce freestanding three-dimensional turbostratic graphene (bi-3DG) monoliths with high specific surface area. Scanning electron microscopy (SEM) images show that the bi-3DG monoliths inherit the unique microstructural characteristics of their bijel parents. Processing of the Ni templates strongly influences the resultant bi-3DG structures, enabling the formation of stacked graphene flakes or fewer-layer continuous films. Despite the multilayer nature, Raman spectra exhibit no discernable defect peak and large relative intensity for the Raman 2D mode, which is a characteristic of turbostratic graphene. Moiré patterns, observed in scanning tunneling microscopy images, further confirm the presence of turbostratic graphene. Nanoindentation of macroscopic pillars reveals a Young's modulus of 30 MPa, one of the highest recorded for sp2 carbon in a porous structure. Overall, this work highlights the utility of a scalable self-assembly method towards porous high quality graphene constructs with tunable, uniform, and co-continuous microstructure.
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Affiliation(s)
- Adrian E Garcia
- Department of Materials Science and Engineering, University of California Irvine CA 92697-2585 USA
| | - Chen Santillan Wang
- Department of Materials Science and Engineering, University of California Irvine CA 92697-2585 USA
| | - Robert N Sanderson
- Department of Physics and Astronomy, University of California Irvine CA 92697-4575 USA
| | - Kyle M McDevitt
- Department of Materials Science and Engineering, University of California Irvine CA 92697-2585 USA
| | - Yunfei Zhang
- Department of Mechanical and Aerospace Engineering, University of California Irvine CA 92697-2700 USA
| | - Lorenzo Valdevit
- Department of Materials Science and Engineering, University of California Irvine CA 92697-2585 USA
- Department of Mechanical and Aerospace Engineering, University of California Irvine CA 92697-2700 USA
| | - Daniel R Mumm
- Department of Materials Science and Engineering, University of California Irvine CA 92697-2585 USA
| | - Ali Mohraz
- Department of Chemical and Biomolecular Engineering, University of California Irvine CA 92697-2580 USA
| | - Regina Ragan
- Department of Materials Science and Engineering, University of California Irvine CA 92697-2585 USA
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Bauer J, Meza LR, Schaedler TA, Schwaiger R, Zheng X, Valdevit L. Nanolattices: An Emerging Class of Mechanical Metamaterials. Adv Mater 2017; 29. [PMID: 28873250 DOI: 10.1002/adma.201701850] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 05/23/2017] [Indexed: 05/12/2023]
Abstract
In 1903, Alexander Graham Bell developed a design principle to generate lightweight, mechanically robust lattice structures based on triangular cells; this has since found broad application in lightweight design. Over one hundred years later, the same principle is being used in the fabrication of nanolattice materials, namely lattice structures composed of nanoscale constituents. Taking advantage of the size-dependent properties typical of nanoparticles, nanowires, and thin films, nanolattices redefine the limits of the accessible material-property space throughout different disciplines. Herein, the exceptional mechanical performance of nanolattices, including their ultrahigh strength, damage tolerance, and stiffness, are reviewed, and their potential for multifunctional applications beyond mechanics is examined. The efficient integration of architecture and size-affected properties is key to further develop nanolattices. The introduction of a hierarchical architecture is an effective tool in enhancing mechanical properties, and the eventual goal of nanolattice design may be to replicate the intricate hierarchies and functionalities observed in biological materials. Additive manufacturing and self-assembly techniques enable lattice design at the nanoscale; the scaling-up of nanolattice fabrication is currently the major challenge to their widespread use in technological applications.
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Affiliation(s)
- Jens Bauer
- Department of Mechanical and Aerospace Engineering, University of California Irvine, CA, 92697, USA
- Institute for Applied Materials, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, 76344, Germany
| | - Lucas R Meza
- Engineering Department, Trumpington Street, Cambridge, CB2 1PZ, UK
| | | | - Ruth Schwaiger
- Institute for Applied Materials, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, 76344, Germany
| | - Xiaoyu Zheng
- Department of Mechanical Engineering, Virginia Tech, 635 Prices Fork Road, Blacksburg, VA, 24061, USA
| | - Lorenzo Valdevit
- Department of Mechanical and Aerospace Engineering, University of California Irvine, CA, 92697, USA
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Haghpanah B, Salari-Sharif L, Pourrajab P, Hopkins J, Valdevit L. Multistable Shape-Reconfigurable Architected Materials. Adv Mater 2016; 28:7915-7920. [PMID: 27384125 DOI: 10.1002/adma.201601650] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Revised: 05/27/2016] [Indexed: 05/19/2023]
Abstract
Multistable shape-reconfigurable architected materials encompassing living hinges and enabling combinations of high strength, high volumetric change, and complex shape-morphing patterns are introduced. Analytical and numerical investigations, validated by experiments, are performed to characterize the mechanical behavior of the proposed materials. The proposed architected materials can be constructed from virtually any base material, at any length scale and dimensionality.
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Affiliation(s)
- Babak Haghpanah
- Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA, USA, 92697
| | - Ladan Salari-Sharif
- Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA, USA, 92697
| | - Peyman Pourrajab
- Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA, USA, 92697
| | - Jonathan Hopkins
- Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, CA, USA, 90095
| | - Lorenzo Valdevit
- Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA, USA, 92697.
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Kurup A, Ravindranath S, Tran T, Keating M, Gascard P, Valdevit L, Tlsty TD, Botvinick EL. Novel insights from 3D models: the pivotal role of physical symmetry in epithelial organization. Sci Rep 2015; 5:15153. [PMID: 26472542 PMCID: PMC4608012 DOI: 10.1038/srep15153] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 09/15/2015] [Indexed: 12/19/2022] Open
Abstract
3D tissue culture models are utilized to study breast cancer and other pathologies because they better capture the complexity of in vivo tissue architecture compared to 2D models. However, to mimic the in vivo environment, the mechanics and geometry of the ECM must also be considered. Here, we studied the mechanical environment created in two 3D models, the overlay protocol (OP) and embedded protocol (EP). Mammary epithelial acini features were compared using OP or EP under conditions known to alter acinus organization, i.e. collagen crosslinking and/or ErbB2 receptor activation. Finite element analysis and active microrheology demonstrated that OP creates a physically asymmetric environment with non-uniform mechanical stresses in radial and circumferential directions. Further contrasting with EP, acini in OP displayed cooperation between ErbB2 signalling and matrix crosslinking. These differences in acini phenotype observed between OP and EP highlight the functional impact of physical symmetry in 3D tissue culture models.
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Affiliation(s)
- Abhishek Kurup
- University of California Irvine, Department of Biomedical Engineering, Irvine, USA
| | - Shreyas Ravindranath
- University of California Irvine, Department of Biomedical Engineering, Irvine, USA
| | - Tim Tran
- University of California Irvine, Department of Biomedical Engineering, Irvine, USA
| | - Mark Keating
- University of California Irvine, Department of Biomedical Engineering, Irvine, USA
| | - Philippe Gascard
- University of California San Francisco, Department of Pathology, San Francisco, USA
| | - Lorenzo Valdevit
- University of California Irvine, Department of Mechanical and Aerospace Engineering, Irvine, USA
| | - Thea D Tlsty
- University of California San Francisco, Department of Pathology, San Francisco, USA
| | - Elliot L Botvinick
- University of California Irvine, Department of Biomedical Engineering, Irvine, USA.,University of California Irvine, Department of Surgery, Irvine, USA
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Abstract
Ultralight (<10 milligrams per cubic centimeter) cellular materials are desirable for thermal insulation; battery electrodes; catalyst supports; and acoustic, vibration, or shock energy damping. We present ultralight materials based on periodic hollow-tube microlattices. These materials are fabricated by starting with a template formed by self-propagating photopolymer waveguide prototyping, coating the template by electroless nickel plating, and subsequently etching away the template. The resulting metallic microlattices exhibit densities ρ ≥ 0.9 milligram per cubic centimeter, complete recovery after compression exceeding 50% strain, and energy absorption similar to elastomers. Young's modulus E scales with density as E ~ ρ(2), in contrast to the E ~ ρ(3) scaling observed for ultralight aerogels and carbon nanotube foams with stochastic architecture. We attribute these properties to structural hierarchy at the nanometer, micrometer, and millimeter scales.
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Affiliation(s)
- T A Schaedler
- HRL Laboratories Limited Liability Company, Malibu, CA 90265, USA.
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Lian J, Jang D, Valdevit L, Schaedler TA, Jacobsen AJ, B Carter W, Greer JR. Catastrophic vs gradual collapse of thin-walled nanocrystalline Ni hollow cylinders as building blocks of microlattice structures. Nano Lett 2011; 11:4118-4125. [PMID: 21851060 DOI: 10.1021/nl202475p] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Lightweight yet stiff and strong lattice structures are attractive for various engineering applications, such as cores of sandwich shells and components designed for impact mitigation. Recent breakthroughs in manufacturing enable efficient fabrication of hierarchically architected microlattices, with dimensional control spanning seven orders of magnitude in length scale. These materials have the potential to exploit desirable nanoscale-size effects in a macroscopic structure, as long as their mechanical behavior at each appropriate scale - nano, micro, and macro levels - is properly understood. In this letter, we report the nanomechanical response of individual microlattice members. We show that hollow nanocrystalline Ni cylinders differing only in wall thicknesses, 500 and 150 nm, exhibit strikingly different collapse modes: the 500 nm sample collapses in a brittle manner, via a single strain burst, while the 150 nm sample shows a gradual collapse, via a series of small and discrete strain bursts. Further, compressive strength in 150 nm sample is 99.2% lower than predicted by shell buckling theory, likely due to localized buckling and fracture events observed during in situ compression experiments. We attribute this difference to the size-induced transition in deformation behavior, unique to nanoscale, and discuss it in the framework of "size effects" in crystalline strength.
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Affiliation(s)
- Jie Lian
- Division of Engineering and Applied Sciences, California Institute of Technology , 1200 East California Boulevard, MC 309-81, Pasadena, California 91125-8100, United States.
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Gamero-Castaño M, Torrents A, Valdevit L, Zheng JG. Pressure-induced amorphization in silicon caused by the impact of electrosprayed nanodroplets. Phys Rev Lett 2010; 105:145701. [PMID: 21230843 DOI: 10.1103/physrevlett.105.145701] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 08/31/2010] [Indexed: 05/30/2023]
Abstract
This Letter describes the shock-induced amorphization of single-crystal Si bombarded by nanodroplets. At impact velocities of several kilometers per second, the projectiles trigger strong compression pulses lasting tens of picoseconds. The phase transition, confirmed via transmission electron microscopy and electron backscatter diffraction, takes place when the projectile's stagnation pressure is approximately 15 GPa. We speculate that the amorphization results either from the decompression of the β-Sn phase or during the compression of the diamond phase.
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Affiliation(s)
- Manuel Gamero-Castaño
- Department of Mechanical and Aerospace Engineering, University of California, Irvine, California 92697, USA.
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