Elastic microphase separation produces robust bicontinuous materials.

Bicontinuous microstructures are essential to the function of diverse natural and synthetic systems. Their synthesis has been based on two approaches: arrested phase separation or self-assembly of block copolymers. The former is attractive for its chemical simplicity and the latter, for its thermodynamic robustness. Here we introduce elastic microphase separation (EMPS) as an alternative approach to make bicontinuous microstructures. Conceptually, EMPS balances the molecular-scale forces that drive demixing with large-scale elasticity to encode a thermodynamic length scale. This process features a continuous phase transition, reversible without hysteresis. Practically, EMPS is triggered by simply supersaturating an elastomeric matrix with a liquid, resulting in uniform bicontinuous materials with a well-defined microscopic length scale tuned by the matrix stiffness. The versatility of EMPS is further demonstrated by fabricating bicontinuous materials with superior mechanical properties and controlled anisotropy and microstructural gradients. Overall, EMPS presents a robust alternative for the bulk fabrication of homogeneous bicontinuous materials.

Effect of curvature on the diffusion of colloidal bananas.

Anisotropic colloidal particles exhibit complex dynamics which play a crucial role in their functionality, transport, and phase behavior. In this Letter, we investigate the two-dimensional diffusion of smoothly curved colloidal rods-also known as colloidal bananas-as a function of their opening angle α. We measure the translational and rotational diffusion coefficients of the particles with opening angles ranging from 0^{∘} (straight rods) to nearly 360^{∘}(closed rings). In particular, we find that the anisotropic diffusion of the particles varies nonmonotonically with their opening angle and that the axis of fastest diffusion switches from the long to the short axis of the particles when α>180^{∘}. We also find that the rotational diffusion coefficient of nearly closed rings is approximately an order of magnitude higher than that of straight rods of the same length. Finally, we show that the experimental results are consistent with slender body theory, indicating that the dynamical behavior of the particles arises primarily from their local drag anisotropy. These results highlight the impact of curvature on the Brownian motion of elongated colloidal particles, which must be taken into account when seeking to understand the behavior of curved colloidal particles.

Putting the Squeeze on Phase Separation.

Phase separation is a ubiquitous process and finds applications in a variety of biological, organic, and inorganic systems. Nature has evolved the ability to control phase separation to both regulate cellular processes and make composite materials with outstanding mechanical and optical properties. Striking examples of the latter are the vibrant blue and green feathers of many bird species, which are thought to result from an exquisite control of the size and spatial correlations of their phase-separated microstructures. By contrast, it is much harder for material scientists to arrest and control phase separation in synthetic materials with such a high level of precision at these length scales. In this Perspective, we briefly review some established methods to control liquid-liquid phase separation processes and then highlight the emergence of a promising arrest method based on phase separation in an elastic polymer network. Finally, we discuss upcoming challenges and opportunities for fabricating microstructured materials via mechanically controlled phase separation.

Hierarchical self-assembly of polydisperse colloidal bananas into a two-dimensional vortex phase.

Self-assembly of microscopic building blocks into highly ordered and functional structures is ubiquitous in nature and found at all length scales. Hierarchical structures formed by colloidal building blocks are typically assembled from monodisperse particles interacting via engineered directional interactions. Here, we show that polydisperse colloidal bananas self-assemble into a complex and hierarchical quasi-two-dimensional structure, called the vortex phase, only due to excluded volume interactions and polydispersity in the particle curvature. Using confocal microscopy, we uncover the remarkable formation mechanism of the vortex phase and characterize its exotic structure and dynamics at the single-particle level. These results demonstrate that hierarchical self-assembly of complex materials can be solely driven by entropy and shape polydispersity of the constituting particles.

Synthesis of Rough Colloidal SU-8 Rods and Bananas via Nanoprecipitation.

Surface roughness plays an important role in determining the mechanical properties, wettability, and self-assembly in colloidal systems. In this work, we develop a simple and fast method to produce rough colloidal SU-8 rods, bananas, and spheres, via the nanoprecipitation of SU-8 in water. During this process, SU-8 nanospheres are absorbed onto the surface of the colloidal SU-8 particles and then cross-linked using UV-light. The size of the spherical asperities and the asperity density are controlled by the concentration of SU-8 used during the nanoprecipitation reaction. Fluorescent labeling of the rough SU-8 colloidal particles allows for their confocal imaging, which demonstrates their stability at high packing fractions. With these newly developed rough particles, we provide a colloidal model system that allows for studies addressing the impact of surface roughness on materials composed of anisotropic particles.

Shaping colloidal bananas to reveal biaxial, splay-bend nematic, and smectic phases.

Understanding the impact of curvature on the self-assembly of elongated microscopic building blocks, such as molecules and proteins, is key to engineering functional materials with predesigned structure. We develop model "banana-shaped" colloidal particles with tunable dimensions and curvature, whose structure and dynamics are accessible at the particle level. By heating initially straight rods made of SU-8 photoresist, we induce a controllable shape deformation that causes the rods to buckle into banana-shaped particles. We elucidate the phase behavior of differently curved colloidal bananas using confocal microscopy. Although highly curved bananas only form isotropic phases, less curved bananas exhibit very rich phase behavior, including biaxial nematic phases, polar and antipolar smectic-like phases, and even the long-predicted, elusive splay-bend nematic phase.

Update in infectious diseases 2019

The IX Course of Antimicrobials and Infectious Diseases update included a review of the main issues in clinical microbiology, epidemiology and clinical aspects for a current approach of infectious pathology. The present introduction summarizes about the most important meetings related to infectious diseases during 2018 (ECCMID, IAS, ASM and ID Week). In addition, the course provides a practical information to focus on nosocomial infection models, with immunosuppressed patients or complex multidrug-resistant pathogens. The closing lecture of this year reviewed the infection during donation process

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Synthesis of Colloidal SU-8 Polymer Rods Using Sonication.

The bulk synthesis of fluorescent colloidal SU-8 polymer rods with tunable dimensions is described. The colloidal SU-8 rods are prepared by shearing an emulsion of SU-8 polymer droplets and then exposing the resulting non-Brownian rods to ultrasonic waves, which breaks them into colloidal rods with typical lengths of 3.5-10 µm and diameters of 0.4-1 µm. The rods are stable in both aqueous and apolar solvents, and by varying the composition of apolar solvent mixtures both the difference in refractive index and mass density between particles and solvent can be independently controlled. Consequently, these colloidal SU-8 rods can be used in both 3D confocal microscopy and optical trapping experiments while carefully tuning the effect of gravity. This is demonstrated by using confocal microscopy to image the liquid crystalline phases and the isotropic-nematic interface formed by the colloidal SU-8 rods and by optically trapping single rods in water. Finally, the simultaneous confocal imaging and optical manipulation of multiple SU-8 rods in the isotropic phase is shown.

Wet-Chemical Synthesis of Chiral Colloids.

We disclose a method for the synthesis of chiral colloids from spontaneously formed hollow sugar-surfactant microtubes with internally confined mobile colloidal spheres. Key feature of our approach is the grafting of colloid surfaces with photoresponsive coumarin moieties, which allow for UV-induced, covalent clicking of colloids into permanent chains, with morphologies set by the colloid-to-tube diameter ratio. Subsequent dissolution of tube confinement yields aqueous suspensions that comprise bulk quantities of a variety of linear chains, including single helical chains of polystyrene colloids. These colloidal equivalents of chiral (DNA) molecules are intended for microscopic study of chiral dynamics on a single-particle level.

Highlights in ASM MICROBE 2017 (New Orleans)

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Update in Infectious Diseases 2017 / Actualización en patología infecciosa 2017

Antimicrobial resistance in complex models of continuous infection is a current issue. The update 2017 course addresses about microbiological, epidemiological and clinical aspects useful for a current approach to infectious disease. During the last year, nosocomial pneumonia approach guides, recommendations for management of yeast and filamentous fungal infections, review papers on the empirical approach to peritonitis and extensive guidelines on stewardship have been published. HIV infection is being treated before and more intensively. The implementation of molecular biology, spectrometry and inmunology to traditional techniques of staining and culture achieve a better and faster microbiological diagnosis. Finally, the infection is increasingly integrated, assessing non-antibiotic aspects in the treatment (AU)

La resistencia a los antimicrobianos en modelos cada vez más complejos de infección continúa siendo actualidad. El curso de actualización de este año 2017 trata aspectos microbiológicos, epidemiológicos y clínicos útiles para un abordaje actual de la patología infecciosa. Durante el último año se han publicado guías de aproximación a la neumonía nosocomial, recomendaciones sobre el manejo de la infección fúngica por levaduras y filamentosos, documentos de revisión sobre el abordaje empírico de la peritonitis y una extensas guías sobre stewardship. En la infección por el VIH, cada vez se trata antes y más intensamente. La implementación de la biología molecular, la espectrometría y la inmunología a las técnicas tradicionales de tinción y cultivo consiguen un diagnóstico microbiológico mejor y más rápido. Por último, la infección se aborda de forma cada vez más integral, valorando aspectos no antibióticos en el tratamiento (AU)