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We report on the design and implementation of an evaporation blocker for cone-plate and plate-plate geometries. In addition to minimizing sample evaporation by trapping the saturated vapor inside a sample chamber, an important feature of the evaporation blocker is the suppression of solvent transport through condensation. Validation tests with DI-water, hydrogels, and colloidal suspensions demonstrate that the new accessory reduces solvent evaporation significantly more than commercially available environmental control chambers. Experiments were also performed to show that the evaporation blocker enables a variety of experiments on thermoresponsive complex fluids that were previously impossible, and provide new insight into the molecular organization of these materials. The evaporation blocker was specifically designed for an Anton Paar MCR rheometer, but the fundamental principles are widely applicable.

We report an in situ method for three-dimensionally resolved temperature measurement in microsystems. The temperature of the surrounding fluid is correlated from Brownian diffusion of suspended nanoparticles. We use video-microscopy in combination with image analysis software to selectively track nanoparticles in the focal plane. This method is superior with regards to reproducibility and reduced systematic errors since measuring Brownian diffusivity does not rely on fluorescence intensity or lifetime of fluorophores. The efficacy of the method is demonstrated by measuring spatial temperature profiles in various microfluidic devices that generate temperature gradients and by comparing these results with numerical simulations. We show that the method is accurate and can be used to extract spatial temperature variations in three dimensions. Compared to conventional methods that require expensive multiphoton optical sectioning setups, this technique is simple and inexpensive. In addition, we demonstrate the capability of this method as an in situ tool for simultaneously observing live cells under the microscope and monitoring the local temperature of the cell medium without biochemical interference, which is crucial for quantitative studies of cells in microfluidic devices.

The stability and properties of dilute solution hydrogels, synthesized by transition metal mediated polymerization of amino acid N-carboxyanhydrides(NCAs) is studied in deionized (DI) water as well as various ionic media. Unique mechanism of gelation displayed in amphiphilic block co-polypeptide hydrogels was found to impart these materials with a number of desireable properties.

Author(s): Andrew P. Nowak [1, 2]; Victor Breedveld [2, 3]; Lisa Pakstis [4]; Bulent Ozbas [4]; David J. Pine [2, 3]; Darrin Pochan [4]; Timothy J. Deming (corresponding author) [1, [...]

We introduce and demonstrate critical steps toward the Geode process for the bottom-up synthesis of semiconductor nanowires. Central to the process is the design and fabrication of an unconventional, high surface area substrate: the interior surface of hollow silica microcapsules, assembled from silica particles via emulsion templating, and featuring porous walls to enable efficient gas transport. The interior surface of these hollow silica microcapsules is decorated with gold nanoparticles that seed nanowire growth via the vapor–liquid–solid (VLS) mechanism. We demonstrate the production of the necessary microcapsules and show how microcapsule structure and stability upon drying are influenced by the type of silica particles and use of a particle cross-linking agent. Finally, we demonstrate the synthesis of crystalline Si nanowires in the microcapsule interior. [ABSTRACT FROM AUTHOR]