A 3-dimensional fibre scaffold as an investigative tool for studying the morphogenesis of isolated plant pells.

BACKGROUND: Cell culture methods allow the detailed observations of individual plant cells and their internal processes. Whereas cultured cells are more amenable to microscopy, they have had limited use when studying the complex interactions between cell populations and responses to external signals associated with tissue and whole plant development. Such interactions result in the diverse range of cell shapes observed in planta compared to the simple polygonal or ovoid shapes in vitro. Microfluidic devices can isolate the dynamics of single plant cells but have restricted use for providing a tissue-like and fibrous extracellular environment for cells to interact. A gap exists, therefore, in the understanding of spatiotemporal interactions of single plant cells interacting with their three-dimensional (3D) environment. A model system is needed to bridge this gap. For this purpose we have borrowed a tool, a 3D nano- and microfibre tissue scaffold, recently used in biomedical engineering of animal and human tissue physiology and pathophysiology in vitro. RESULTS: We have developed a method of 3D cell culture for plants, which mimics the plant tissue environment, using biocompatible scaffolds similar to those used in mammalian tissue engineering. The scaffolds provide both developmental cues and structural stability to isolated callus-derived cells grown in liquid culture. The protocol is rapid, compared to the growth and preparation of whole plants for microscopy, and provides detailed subcellular information on cells interacting with their local environment. We observe cell shapes never observed for individual cultured cells. Rather than exhibiting only spheroid or ellipsoidal shapes, the cells adapt their shape to fit the local space and are capable of growing past each other, taking on growth and morphological characteristics with greater complexity than observed even in whole plants. Confocal imaging of transgenic Arabidopsis thaliana lines containing fluorescent microtubule and actin reporters enables further study of the effects of interactions and complex morphologies upon cytoskeletal organisation both in 3D and in time (4D). CONCLUSIONS: The 3D culture within the fibre scaffolds permits cells to grow freely within a matrix containing both large and small spaces, a technique that is expected to add to current lithographic technologies, where growth is carefully controlled and constricted. The cells, once seeded in the scaffolds, can adopt a variety of morphologies, demonstrating that they do not need to be part of a tightly packed tissue to form complex shapes. This points to a role of the immediate nano- and micro-topography in plant cell morphogenesis. This work defines a new suite of techniques for exploring cell-environment interactions

Magnetic actuation and transition shapes of a bistable spherical cap

Multistable shells have been proposed for a variety of applications; however, their actuation is almost exclusively addressed through embedded piezoelectric patches. Additional actuation techniques are needed for applications requiring high strains or where remote actuation is desirable. Part of the reason for the lack of research in this area is the absence of appropriate models describing the detailed deformation and energetics of such shells. This work presents a bistable spherical cap made of iron carbonyl-infused polydimethylsiloxane. The magnetizable structure can be actuated remotely through permanent magnets while the transition is recorded with a high-speed camera. Moreover, the experiment is reproduced in a finite element (FE) dynamic model for comparison with the physical observations. High-speed footage of the physical cap inversion together with the FE modeling gives valuable insight on preferable intermediate geometries. Both methods return similar values for the magnetic field strength required for the snap-through. High-strain multistable spherical cap transformation is demonstrated, based on informed material selection. We discover that non-axisymmetric transition shapes are preferred in intermediate geometries by bistable spherical caps. We develop the methods for design and analysis of such actuators, including the feasibility of remote actuation methods for multistable shells.EGL acknowledges financial support by the Alexander S. Onassis Public Benefit Foundation and the Cyprus State Scholarship Foundation. SKS acknowledges funding by the European Research Council (ERC) grant EMATTER [#280078].This is the final published version. It first appeared at http://www.tandfonline.com/action/showCopyRight?doi=10.1080%2F19475411.2014.997322#tabModule

Fault-Tolerant Electro-Responsive Surfaces for Dynamic Micropattern Molds and Tunable Optics.

Electrically deformable surfaces based on dielectric elastomers have recently demonstrated controllable microscale roughness, ease of operation, fast response, and possibilities for programmable control. Potential applications include marine anti-biofouling, dynamic pattern generation, and voltage-controlled smart windows. Most of these systems, however, exhibit limited durability due to irreversible dielectric breakdown. Lowering device voltage to avoid this issue is hindered by an inadequate understanding of the electrically-induced wrinkling deformation as a function of the deformable elastic film thickness. Here we report responsive surfaces that overcome these shortcomings: we achieve fault-tolerant behavior based on the ability to self-insulate breakdown faults, and we enhance fundamental understanding of the system by quantifying the critical field necessary to induce wrinkles in films of different thickness and comparing to analytical models. We also observe new capabilities of these responsive surfaces, such as field amplification near local breakdown sites, which enable actuation and wrinkle pattern formation at lower applied voltages. We demonstrate the wide applicability of our responsive, fault-tolerant films by using our system for adjustable transparency films, tunable diffraction gratings, and a dynamic surface template/factory from which various static micropatterns can be molded on demand

Stamping colloidal photonic crystals: a facile way towards complex pixel colour patterns for sensing and displays.

Patterning of colloidal photonic crystals (CPCs) has been strongly investigated in recent years for sensing and image displays. Rather than using traditional template-directed approaches, here microimprint lithography along with convective self-assembly is applied to generate complex CPC patterns that can be adjusted to show single- or dual-colour patterns or composite CPC patterns possessing two different colours. These composite CPC patterns show different wettability with water because of the surface chemistry of the polymers and silica used. This dramatically transforms the structural colours upon liquid infiltration. By mixing different ethanol concentrations with water, the infiltration efficiency can be further improved and easily read out from changes in reflection intensity and spectral peak shifts. Integrating these nano-architectures into devices can thus yield function as image displays and as sensors for solvents.We acknowledge financial support from EPSRC grant EP/ G060649/1, EP/I012060/1, EP/J007552/1, EP/L027151/1, ERC grant LINASS 320503, EMATTER 280078.This is the final published version. The article first appeared at http://pubs.rsc.org/en/Content/ArticleLanding/2015/NR/C4NR05934D#!divAbstract

Symmetry breaking polymerization: one-pot synthesis of plasmonic hybrid Janus nanoparticles.

Asymmetric hybrid nanoparticles have many important applications in catalysis, nanomotion, sensing, and diagnosis, however ways to generate the asymmetric hybrid nanoparticles are quite limited and inefficient. Most current methods rely on interfacial adhesion and modification of already formed particles. In this article we report a one-pot, facile and scalable synthesis of anisotropic Au-polymer hybrid nanoparticles via interfacial oxidative dispersion polymerization. The interfacial nucleation and polymerization lead to spontaneous symmetry breaking and formation of the Janus particles. The reaction is initiated by monomer radicals generated by the strong oxidant HAuCl4, which is itself later reduced by the electron-rich monomers to self-nucleate and form Au nanoparticles (NPs). The competition between divinylbenzene adsorption and the PVP capping agent results in effective partial surface wetting, forming asymmetric Au-PDVB hybrid nanoparticles, by confining growth of each material to its own phase. Such spontaneous symmetry breaking, important in morphogenesis, with control over the subsequent growth processes should lead to significant advances in the synthesis of asymmetric nanostructures.The research was funded by ERC grants EMATTER 280078 and LINASS 320503, and EPSRC grants EP/G060649/1, and EP/ L027151/1.This is the final published version. It first appeared at http://pubs.rsc.org/en/Content/ArticleLanding/2015/NR/c5nr01999k#!divAbstract

Selectively Patterning Polymer Opal Films via Microimprint Lithography.

Large-scale structural color flexible coatings have been hard to create, and patterning color on them is key to many applications, including large-area strain sensors, wall-size displays, security devices, and smart fabrics. To achieve controlled tuning, a micro-imprinting technique is applied here to pattern both the surface morphology and the structural color of the polymer opal films (POFs). These POFs are made of 3D ordered arrays of hard spherical particles embedded inside soft shells. The soft outer shells cause the POFs to deform upon imprinting with a pre-patterned stamp, driving a flow of the soft polymer and a rearrangement of the hard spheres within the films. As a result, a patterned surface morphology is generated within the POFs and the structural colors are selectively modified within different regions. These changes are dependent on the pressure, temperature, and duration of imprinting, as well as the feature sizes in the stamps. Moreover, the pattern geometry and structural colors can then be further tuned by stretching. Micropattern color generation upon imprinting depends on control of colloidal transport in a polymer matrix under shear flow and brings many potential properties including stretchability and tunability, as well as being of fundamental interest.This is the final version. It was first published in Advanced Optical Materials by Wiley at http://onlinelibrary.wiley.com/doi/10.1002/adom.201400327/abstract

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

Background: Cell culture methods allow the detailed observations of individual plant cells and their internal processes. Whereas cultured cells are more amenable to microscopy, they have had limited use when studying the complex interactions between cell populations and responses to external signals associated with tissue and whole plant development. Such interactions result in the diverse range of cell shapes observed in planta compared to the simple polygonal or ovoid shapes in vitro. Microfluidic devices can isolate the dynamics of single plant cells but have restricted use for providing a tissue-like and fibrous extracellular environment for cells to interact. A gap exists, therefore, in the understanding of spatiotemporal interactions of single plant cells interacting with their three-dimensional (3D) environment. A model system is needed to bridge this gap. For this purpose we have borrowed a tool, a 3D nano- and microfibre tissue scaffold, recently used in biomedical engineering of animal and human tissue physiology and pathophysiology in vitro. Results: We have developed a method of 3D cell culture for plants, which mimics the plant tissue environment, using biocompatible scaffolds similar to those used in mammalian tissue engineering. The scaffolds provide both developmental cues and structural stability to isolated callus-derived cells grown in liquid culture. The protocol is rapid, compared to the growth and preparation of whole plants for microscopy, and provides detailed subcellular information on cells interacting with their local environment. We observe cell shapes never observed for individual cultured cells. Rather than exhibiting only spheroid or ellipsoidal shapes, the cells adapt their shape to fit the local space and are capable of growing past each other, taking on growth and morphological characteristics with greater complexity than observed even in whole plants. Confocal imaging of transgenic Arabidopsis thaliana lines containing fluorescent microtubule and actin reporters enables further study of the effects of interactions and complex morphologies upon cytoskeletal organisation both in 3D and in time (4D). Conclusions: The 3D culture within the fibre scaffolds permits cells to grow freely within a matrix containing both large and small spaces, a technique that is expected to add to current lithographic technologies, where growth is carefully controlled and constricted. The cells, once seeded in the scaffolds, can adopt a variety of morphologies, demonstrating that they do not need to be part of a tightly packed tissue to form complex shapes. This points to a role of the immediate nano- and micro-topography in plant cell morphogenesis. This work defines a new suite of techniques for exploring cell-environment interactions

Revealing Invisible Photonic Inscriptions: Images from Strain.

Photonic structural materials have received intensive interest and have been strongly developed over the past few years for image displays, sensing, and anticounterfeit materials. Their "smartness" arises from their color responsivity to changes of environment, strain, or external fields. Here, we introduce a novel invisible photonic system that reveals encrypted images or characters by simply stretching, or immersing in solvents. This type of intriguing photonic material is composed of regularly arranged core-shell particles that are selectively cross-linked by UV irradiation, giving different strain response compared to un-cross-linked regions. The images reversibly appear and disappear when cycling the strain and releasing it. The unique advantages of this soft polymer opal system compared with other types of photonic gels are that it can be produced in roll to roll quantities, can be vigorously deformed to achieve strong color changes, and has no solvent evaporation issues because it is a photonic rubber system. We demonstrate potential applications together with a fabrication procedure which is straightforward and scalable, vital for user take-up. Our work deepens understanding of this rubbery photonic system based on core-shell nanospheres.We acknowledge financial support from EPSRC grant EP/G060649/1, EP/I012060/1, EP/J007552/1, ERC grant LINASS 320503, EMATTER 280078.This is the accepted manuscript. The final version is available at http://pubs.acs.org/doi/abs/10.1021/acsami.5b02768

Functional conductive nanomaterials via polymerisation in nano-channels: PEDOT in a MOF.

Reactions inside the pores of metal-organic frameworks (MOFs) offer potential for controlling polymer structures with regularity to sub-nanometre scales. We report a wet-chemistry route to poly-3,4-ethylenedioxythiophene (PEDOT)-MOF composites. After a two-step removal of the MOF template we obtain unique and stable macroscale structures of this conductive polymer with some nanoscale regularity.The project is funded through the European Research Council (ERC) grant (grant number: EMATTER 280078). AKC thanks the Ras Al Khaimah Center for Advanced Materials (RAK-CAM). JDWM and MF acknowledge funding through a Discovery Grant from The Natural Sciences and Engineering Research Council of Canada (NSERC). TW thanks the China Scholarship Council (CSC) for funding and the Engineering and Physical Sciences Research Council of the UK (EPSRC) Centre for Doctoral Training in Sensor Technologies and Applications (grant number: EP/L015889/1) for support. SH acknowledges the Alexander von Humboldt Foundation for funding. SS is funded through a scholarship from the Cambridge Overseas Trust. JSB thanks the Isaac Newton Trust for financial support for the FEI Tecnait TEM. The authors would also like to show the gratitude to Phenom-World for the use of the Phenom Pro X SEM and Dr Suman-Lata Sahonta for the help with Raman spectroscopy.This is the final version of the article. It first appeared from the Royal Society of Chemistry at http://dx.doi.org/10.1039/c6mh00230g