12 research outputs found

    Independence of Primary and Secondary Structures in Periodic Precipitation Patterns

    No full text
    Microscopic periodic precipitation patterns featuring both primary and secondary bands form in thin gel films. The initial conditions for the precipitation process are defined by wet stamping and are chosen such that the primary and secondary structures are not necessarily collinear; the fact that these structures propagate in different directions suggests that they form independently of one another. This hypothesis is further supported by a theoretical model in which two different intermediate species mediate band formation

    Additional file 3: of A 3-dimensional fibre scaffold as an investigative tool for studying the morphogenesis of isolated plant cells

    No full text
    A Windows Media movie Movie S2.avi showing a 824 4D dataset of microtubule dynamics. White arrow shows the plus end 825 of an individual microtubule undergoing rounds of growth (polymerisation) 826 and catastrophe (depolymerisation). (AVI 699 kb

    Additional file 2: of A 3-dimensional fibre scaffold as an investigative tool for studying the morphogenesis of isolated plant cells

    No full text
    An Apple Quicktime movie named Movie S1.mov 820 showing a 3D reconstruction of confocal z-stack of microtubule 821 organisation in a rounded cell existing and interacting between two 822 individual fibres. (MOV 5686 kb

    Additional file 1: Figures S1-S9. of A 3-dimensional fibre scaffold as an investigative tool for studying the morphogenesis of isolated plant cells

    No full text
    Figure S1. Projections of confocal z-stacks of Arabidopsis thaliana cells containing the microtubule reporter construct 35S::GFP-MBD: (a-b) immediately before seeding into scaffolds; (b-e) at day 2, 6 and 11 of scaffold incubation. Scale bars: 100 µm. Figure S2. Scaffold morphology observed under SEM (a) before treatment, (b) after UV treatment, (c) after 18 min X-Ray treatment, (d) after immersion in ethanol for 2 hr. Extensive nanofibre fusion is observed in (d). Scale bars: 400 µm. Figure S3. SEM image of a seeded scaffold incubated in growth medium under constant agitation. Arrows indicate small, round and immobilised cells of 47 ± 8 µm. Scale bar: 500 µm. Figure S4. Silica beads (diameter range 40–200 µm, 2.5 x 104 beads per ml-1 in MS growth medium) trapped in the scaffold (a) before and (b) after constant agitation at 130 RPM for 3 days. Scale bars: 100 µm. Figure S5. DIC microscopy of a cell culture free from seed-mucilage contamination. Images show a cell wrapping around a microfibre and interacting with neighbouring fibres. Depth of view: (a) 0 µm, (b) 7.2 µm. Arrows indicate cell-fibre interaction. Red lines highlight relevant microfibres. Scale bars: 100 µm. Figure S6. Spiral growth of a cell around a microfibre. Red lines highlight locations of microfibers. (a) Actin reporter (b) transmission. Scale bars: 100 µm. Figure S7. Confocal z-projections showing GFP-labelled microtubule patterns in A. thaliana cells expressing the reporter construct 35S::GFP-MBD. White arrows indicate microtubules aligned parallel with the principal growth direction. Main panel scale bar: 100 µm. Figure S8. Confocal (a-b, showing autofluorescent cells and microfibres) and high vacuum SEM (c-d, greyscale) images of mesophyll cells of Zinnia elegans cultured in scaffolds at day 3 after seeding. Arrows indicate cell-fibre interactions. Scale bars: 100 µm. Figure S9. Arabidopsis cells expressing DR5::GFP-ER in unmodified scaffolds (a GFP, b transmission, cell outlines are indicated by arrowheads) and in scaffolds encapsulated with the synthetic auxin 2,4-D (c). Scale bars: 100 µm (d) Cell-scaffold PIN7-GFP is observed in discrete punctae (arrows) and the localisation does not differ from cells in liquid culture (data not shown). Scale bar: 10 µm

    Anisotropic Colloidal Micromuscles from Liquid Crystal Elastomers

    No full text
    Monodomain liquid crystal elastomers (LCEs) are new materials uniquely suitable for artificial muscles, as they undergo large reversible uniaxial shape changes, with strains of 20–500% and stresses of 10–100 kPa, falling exactly into the dynamic range of a muscle. LCEs exhibit little to no fatigue over thousands of actuation cycles. Their practical use has been limited, however, owing to the difficulty of synthesizing components, achieving consistent alignment during cross-linking across the whole material and often a high nematic-isotropic phase transition temperature. The most widely studied method for LC alignment involves mechanical stretching of the material during one of two cross-linking steps, which makes fabrication difficult to control and lends itself mainly to samples that can be easily grasped (with sizes of the order of mm). In this article, we describe a method of adapting the LCE synthesis to microscale objects, achieving monodomain alignment with a single cross-linking step, and lowering the cycling temperature. LCE precursor droplets are embedded in and then stretched in a polymer matrix at high temperature. Confinement of the uniaxially stretched droplets maintains the alignment achieved during stretching and allows us to eliminate one of the cross-linking steps and the variability associated with it. Adding a comonomer during the polymerization leads to lowering of the nematic-to-isotropic transition temperature (58 °C), significantly expanding the range of potential applications for these micromuscles. We demonstrate reversible thermal switching of the micromuscles in line with the largest strain changes observed for side-chain LCEs and a differential scanning calorimetry characterization of the material phase transitions. The method demonstrates the parallel fabrication of many microscale actuators and is amenable to further scale-up and manufacturing

    “Self-Shaping” of Multicomponent Drops

    No full text
    In our recent study we showed that single-component emulsion drops, stabilized by proper surfactants, can spontaneously break symmetry and transform into various polygonal shapes during cooling [Denkov Nature 2015, 528, 392−395]. This process involves the formation of a plastic rotator phase of self-assembled oil molecules beneath the drop surface. The plastic phase spontaneously forms a frame of plastic rods at the oil drop perimeter which supports the polygonal shapes. However, most of the common substances used in industry appear as mixtures of molecules rather than pure substances. Here we present a systematic study of the ability of multicomponent emulsion drops to deform upon cooling. The observed trends can be summarized as follows: (1) The general drop-shape evolution for multicomponent drops during cooling is the same as with single-component drops; however, some additional shapes are observed. (2) Preservation of the particle shape upon freezing is possible for alkane mixtures with chain length difference Δ<i>n</i> ≤ 4; for greater Δ<i>n</i>, phase separation within the droplet is observed. (3) Multicomponent particles prepared from alkanes with Δ<i>n</i> ≤ 4 plastify upon cooling due to the formation of a bulk rotator phase within the particles. (4) If a compound, which cannot induce self-shaping when pure, is mixed with a certain amount of a compound which induces self-shaping, then drops prepared from this mixture can also self-shape upon cooling. (5) Self-emulsification phenomena are also observed for multicomponent drops. In addition to the three recently reported mechanisms of self-emulsification [Tcholakova Nat. Commun. 2017 (8), 15012], a new (fourth) mechanism is observed upon freezing for alkane mixtures with Δ<i>n</i> > 4. It involves disintegration of the particles due to a phase separation of alkanes upon freezing

    Video_5_Low Fatigue Dynamic Auxetic Lattices With 3D Printable, Multistable, and Tuneable Unit Cells.mov

    No full text
    <p>Stress distribution has led to the design of both tough and lightweight materials. Truss structures distribute stress well and are commonly used to design lightweight materials for applications experiencing low strains. In 3D lattices, however, few structures allow high elastic compression and tunable deformation. This is especially true for auxetic material designs, such as the prototypical re-entrant honeycomb with sharp corners, which are particularly susceptible to stress concentrations. There is a pressing need for lightweight lattice designs that are dynamic, as well as resistant to fatigue. Truss designs based on hinged structures exist in nature and delocalize stress rather than concentrating it in small areas. They have inspired us to develop s-hinge shaped elastic unit cell elements from which new classes of architected modular 2D and 3D lattices can be printed or assembled. These lattices feature locally tunable Poisson ratios (auxetic), large elastic deformations without fatigue, as well as mechanical switching between multistable states. We demonstrate 3D printed structures with stress delocalization that enables macroscopic 30% cyclable elastic strains, far exceeding those intrinsic to the materials that constitute them (6%). We also present a simple semi-analytical model of the deformations which is able to predict the mechanical properties of the structures within <5% error of experimental measurements from a few parameters such as dimensions and material properties. Using this model, we discovered and experimentally verified a critical angle of the s-hinge enabling bistable transformations between auxetic and normal materials. The dynamic modeling tools developed here could be used for complex 3D designs from any 3D printable material (metals, ceramics, and polymers). Locally tunable deformation and much higher elastic strains than the parent material would enable the next generation of compact, foldable and expandable structures. Mixing unit cells with different hinge angles, we designed gradient Poisson's ratio materials, as well as ones with multiple stable states where elastic energy can be stored in latching structures, offering prospects for multi-functional designs. Much like the energy efficient Venus flytrap, such structures can store elastic energy and release it on demand when appropriate stimuli are present.</p

    Video_3_Low Fatigue Dynamic Auxetic Lattices With 3D Printable, Multistable, and Tuneable Unit Cells.MP4

    No full text
    <p>Stress distribution has led to the design of both tough and lightweight materials. Truss structures distribute stress well and are commonly used to design lightweight materials for applications experiencing low strains. In 3D lattices, however, few structures allow high elastic compression and tunable deformation. This is especially true for auxetic material designs, such as the prototypical re-entrant honeycomb with sharp corners, which are particularly susceptible to stress concentrations. There is a pressing need for lightweight lattice designs that are dynamic, as well as resistant to fatigue. Truss designs based on hinged structures exist in nature and delocalize stress rather than concentrating it in small areas. They have inspired us to develop s-hinge shaped elastic unit cell elements from which new classes of architected modular 2D and 3D lattices can be printed or assembled. These lattices feature locally tunable Poisson ratios (auxetic), large elastic deformations without fatigue, as well as mechanical switching between multistable states. We demonstrate 3D printed structures with stress delocalization that enables macroscopic 30% cyclable elastic strains, far exceeding those intrinsic to the materials that constitute them (6%). We also present a simple semi-analytical model of the deformations which is able to predict the mechanical properties of the structures within <5% error of experimental measurements from a few parameters such as dimensions and material properties. Using this model, we discovered and experimentally verified a critical angle of the s-hinge enabling bistable transformations between auxetic and normal materials. The dynamic modeling tools developed here could be used for complex 3D designs from any 3D printable material (metals, ceramics, and polymers). Locally tunable deformation and much higher elastic strains than the parent material would enable the next generation of compact, foldable and expandable structures. Mixing unit cells with different hinge angles, we designed gradient Poisson's ratio materials, as well as ones with multiple stable states where elastic energy can be stored in latching structures, offering prospects for multi-functional designs. Much like the energy efficient Venus flytrap, such structures can store elastic energy and release it on demand when appropriate stimuli are present.</p

    Presentation_1_Low Fatigue Dynamic Auxetic Lattices With 3D Printable, Multistable, and Tuneable Unit Cells.pdf

    No full text
    <p>Stress distribution has led to the design of both tough and lightweight materials. Truss structures distribute stress well and are commonly used to design lightweight materials for applications experiencing low strains. In 3D lattices, however, few structures allow high elastic compression and tunable deformation. This is especially true for auxetic material designs, such as the prototypical re-entrant honeycomb with sharp corners, which are particularly susceptible to stress concentrations. There is a pressing need for lightweight lattice designs that are dynamic, as well as resistant to fatigue. Truss designs based on hinged structures exist in nature and delocalize stress rather than concentrating it in small areas. They have inspired us to develop s-hinge shaped elastic unit cell elements from which new classes of architected modular 2D and 3D lattices can be printed or assembled. These lattices feature locally tunable Poisson ratios (auxetic), large elastic deformations without fatigue, as well as mechanical switching between multistable states. We demonstrate 3D printed structures with stress delocalization that enables macroscopic 30% cyclable elastic strains, far exceeding those intrinsic to the materials that constitute them (6%). We also present a simple semi-analytical model of the deformations which is able to predict the mechanical properties of the structures within <5% error of experimental measurements from a few parameters such as dimensions and material properties. Using this model, we discovered and experimentally verified a critical angle of the s-hinge enabling bistable transformations between auxetic and normal materials. The dynamic modeling tools developed here could be used for complex 3D designs from any 3D printable material (metals, ceramics, and polymers). Locally tunable deformation and much higher elastic strains than the parent material would enable the next generation of compact, foldable and expandable structures. Mixing unit cells with different hinge angles, we designed gradient Poisson's ratio materials, as well as ones with multiple stable states where elastic energy can be stored in latching structures, offering prospects for multi-functional designs. Much like the energy efficient Venus flytrap, such structures can store elastic energy and release it on demand when appropriate stimuli are present.</p

    Video_1_Low Fatigue Dynamic Auxetic Lattices With 3D Printable, Multistable, and Tuneable Unit Cells.MP4

    No full text
    <p>Stress distribution has led to the design of both tough and lightweight materials. Truss structures distribute stress well and are commonly used to design lightweight materials for applications experiencing low strains. In 3D lattices, however, few structures allow high elastic compression and tunable deformation. This is especially true for auxetic material designs, such as the prototypical re-entrant honeycomb with sharp corners, which are particularly susceptible to stress concentrations. There is a pressing need for lightweight lattice designs that are dynamic, as well as resistant to fatigue. Truss designs based on hinged structures exist in nature and delocalize stress rather than concentrating it in small areas. They have inspired us to develop s-hinge shaped elastic unit cell elements from which new classes of architected modular 2D and 3D lattices can be printed or assembled. These lattices feature locally tunable Poisson ratios (auxetic), large elastic deformations without fatigue, as well as mechanical switching between multistable states. We demonstrate 3D printed structures with stress delocalization that enables macroscopic 30% cyclable elastic strains, far exceeding those intrinsic to the materials that constitute them (6%). We also present a simple semi-analytical model of the deformations which is able to predict the mechanical properties of the structures within <5% error of experimental measurements from a few parameters such as dimensions and material properties. Using this model, we discovered and experimentally verified a critical angle of the s-hinge enabling bistable transformations between auxetic and normal materials. The dynamic modeling tools developed here could be used for complex 3D designs from any 3D printable material (metals, ceramics, and polymers). Locally tunable deformation and much higher elastic strains than the parent material would enable the next generation of compact, foldable and expandable structures. Mixing unit cells with different hinge angles, we designed gradient Poisson's ratio materials, as well as ones with multiple stable states where elastic energy can be stored in latching structures, offering prospects for multi-functional designs. Much like the energy efficient Venus flytrap, such structures can store elastic energy and release it on demand when appropriate stimuli are present.</p
    corecore