Architected Lattices with High Stiffness and Toughness via Multicore–Shell 3D Printing

Mueller, J. Howard; Raney, Jordan R.; Shea, Kristina; Lewis, Jennifer A.

doi:10.1002/adma.201705001

Cited by 150 publications

(89 citation statements)

References 39 publications

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“…Devices employed in biomedical, soft electronics, optoelectronics, and robotics must often integrate soft functional materials with stiffer structural components. Integrating a broad spectrum of available materials affords large variations in properties with multiple functionalities to meet the demands of many applications . However, large internal stresses concentrate at the interface across materials with divergent properties, leaving the interface vulnerable to mechanical failure .…”

Section: Introductionmentioning

confidence: 99%

Stereolithographic 3D Printing for Deterministic Control over Integration in Dual‐Material Composites

Muralidharan

Uzcategui

McLeod

et al. 2019

Adv Materials Technologies

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A rapid and facile approach to predictably control integration between two materials with divergent properties is introduced. Programmed integration between photopolymerizable soft and stiff hydrogels is investigated due to their promise in applications such as tissue engineering where heterogeneous properties are often desired. The spatial control afforded by grayscale 3D printing is leveraged to define regions at the interface that permit diffusive transport of a second material in‐filled into the 3D printed part. The printing parameters (i.e., effective exposure dose) for the resin are correlated directly to mesh size to achieve controlled diffusion. Applying this information to grayscale exposures leads to a range of distances over which integration is achieved with high fidelity. A prescribed finite distance of integration between soft and stiff hydrogels leads to a 33% increase in strain to failure under tensile testing and eliminates failure at the interface. The feasibility of this approach is demonstrated in a layer‐by‐layer 3D printed part fabricated by stereolithography, which is subsequently infilled with a soft hydrogel containing osteoblastic cells. In summary, this approach holds promise for applications where integration of multiple materials and living cells is needed by allowing precise control over integration and reducing mechanical failure at contrasting material interfaces.

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Section: Introductionmentioning

confidence: 99%

Stereolithographic 3D Printing for Deterministic Control over Integration in Dual‐Material Composites

Muralidharan

Uzcategui

McLeod

et al. 2019

Adv Materials Technologies

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“…To date, direct ink writing, stereolithography, and two‐photon lithography have been used to create porous polymer constructs with highly tunable properties. For example, architected polymer lattices have been produced in several geometries with dense, hollow, and foam‐based struts. In the latter case, however, there was limited control over the bubble size and distribution within each strut, since those lattices were produced via direct foam writing .…”

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confidence: 99%

Architected Polymer Foams via Direct Bubble Writing

et al. 2019

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Polymer foams are cellular solids composed of solid and gas phases, whose mechanical, thermal, and acoustic properties are determined by the composition, volume fraction, and connectivity of both phases. A new high‐throughput additive manufacturing method, referred to as direct bubble writing, for creating polymer foams with locally programmed bubble size, volume fraction, and connectivity is reported. Direct bubble writing relies on rapid generation and patterning of liquid shell–gas core droplets produced using a core–shell nozzle. The printed polymer foams are able to retain their overall shape, since the outer shell of these bubble droplets consist of a low‐viscosity monomer that is rapidly polymerized during the printing process. The transition between open‐ and closed‐cell foams is independently controlled by the gas used, while the foam can be tailored on‐the‐fly by adjusting the gas pressure used to produce the bubble droplets. As exemplars, homogeneous and graded polymer foams in several motifs, including 3D lattices, shells, and out‐of‐plane pillars are fabricated. Conductive composite foams with controlled stiffness for use as soft pressure sensors are also produced.

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“…As such, they are used to design soft solid materials with applications including foodstuff, bio-compatible materials, highly stretchable electronics and soft robotics [7][8][9][10][11][12]. Recently, colloidal gels have been employed to produce novel materials via direct ink writing, a versatile additive manufacturing technique in which shear-thinning fluids are deposited by extrusion through a nozzle [13][14][15]. Extrusion disrupts the gel's equilibrium microstructure until it yields and reorganizes to accommodate the flow process.…”

Section: Introductionmentioning

confidence: 99%

Shear melting and recovery of crosslinkable cellulose nanocrystal–polymer gels

et al. 2019

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Cellulose nanocrystals (CNC) are naturally-derived nanostructures of growing importance for the production of composites having attractive mechanical properties, and offer improved sustainability over purely petroleum-based alternatives. Fabrication of CNC composites typically involves extrusion of CNC suspensions and gels in a variety of solvents, in the presence of additives such as polymers and curing agents. However, most studies so far have focused on aqueous CNC gels, yet the behavior of CNC-polymer gels in organic solvents is important to their wider processability. Here, we study the rheological behavior of composite polymer-CNC gels in dimethylformamide, which include additives for both UV and thermal crosslinking. Using rheometry coupled with in-situ infrared spectroscopy, we show that under external shear, CNC-polymer gels display progressive and irreversible failure of the hydrogen bond network that is responsible for their pronounced elastic properties. In the absence of cross-linking additives, the polymer-CNC gels show negligible recovery upon cessation of flow, while the presence of additives allows the gels to recover via van der Waals interactions. By exploring a broad range of shear history and CNC concentrations, we construct master curves for the temporal evolution of the viscoelastic properties of the polymer-CNC gels, illustrating universality of the observed dynamics with respect to gel composition and flow conditions. We therefore find that polymer-CNC composite gels display a number of the distinctive features of colloidal glasses and, strikingly, that their response to the flow conditions encountered during processing can be tuned by chemical additives. These findings have implications for processing of dense CNC-polymer composites in solvent casting, 3D printing, and other manufacturing techniques. arXiv:1901.04373v1 [cond-mat.soft]

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Architected Lattices with High Stiffness and Toughness via Multicore–Shell 3D Printing

Cited by 150 publications

References 39 publications

Stereolithographic 3D Printing for Deterministic Control over Integration in Dual‐Material Composites

Stereolithographic 3D Printing for Deterministic Control over Integration in Dual‐Material Composites

Architected Polymer Foams via Direct Bubble Writing

Shear melting and recovery of crosslinkable cellulose nanocrystal–polymer gels

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