Calendar of MRSEC Events

Abstract: Over the past few years, mounting interests have been attracted in topics involving intrinsically disordered proteins (IDP). Particularly in the fields of protein engineering, supramolecular self-assembly, functional hydrogels and biomechanics, sophisticated design and manufacturing are realized through amalgamating the IDPs with bioactive components. As one type of the most important IDPs, elastin presents multiple extraordinary properties, including good biomechanical characteristics, biopolymeric phase separation behavior, biodegradability and low immunogenicity. These promising features allow elastin-like proteins to be developed as a new generation of functional biomaterials in the context of cross-disciplinary studies. However, it is challenging to supercharge elastin variants for macroscopic assembly of advanced materials. This talk will highlight recent technical advances and practical applications employing Supercharged elastin-like Proteins (SUPs). First, I will introduce the interplay between SUPs and surfactants and soft matter ensembles generated through the two-component complexation. Second, an artificial tongue consisting of SUPs and polyelectrolyte elements for whiskey discrimination will be underscored. Lastly, a recent finding on etiology of Alzheimer’s disease and elastin would be presented.

Abstract: Gelation of colloidal suspensions plays a crucial role in the formation of numerous solids. Examples range from cement to yogurt, which results respectively from the aggregation of CSH nanoparticles and casein micelles. In both systems, short-range attractive interactions between the particles lead to the formation of a percolated network that is responsible for the solid-like behavior of the material. Generated by a kinetic arrest, these solids are out-of-equilibrium structures, whose properties are sensitive to the route followed during gelation. Indeed, external shear often comes to compete with the attractive interactions that drive the gelation, affecting the gel's microstructure, which encodes the gel's shear history. Such a "memory effect" is, for instance, easily visualized in the various morphologies of crack patterns that form when the gel is left to dry.

Abstract: Self-organization phenomena that lead to pattern formation and synchronization play an important role in biology, chemistry, physics and technological applications. They manifest for example in electrical waves on the heart muscle, fireflies flashing in unison, power-grid blackouts and neurological functions as well as disorders. I will present a versatile experimental setup based on optically coupled catalytic micro-particles, that allows studying synchronization patterns in very large networks of relaxation oscillators under well-controlled laboratory conditions. In particular I will show the experimental verification of the elusive spiral wave chimera state, whose existence was predicted more than 15 years ago. This pattern features a wave rotating around a spatially extended core that consists of phase-randomized oscillators. The spiral wave chimera is likely to play a role in cortical cell ensembles, arrays of SQUIDS and carpets of cilia. Furthermore, these experimental capabilities facilitate the free choice of network topology, coupling function as well as its strength, range and time delay, which can even be chosen as time-dependent. This opens the door to a broad range of future experimental inquiries into pattern formation and synchronization on large networks, which were previously out of reach.

Abstract: Optical techniques can enable non-invasive, in situ measurements of the properties of biologically or industrially relevant colloidal particles. One such property is the fractal dimension of fractal-like aggregates, which can be formed by some proteins when heated. Here, we consider recent experiments that used holographic microscopy, a technique based on optical interference, and an optical scattering model based on an effective-medium theory to determine the fractal dimension of colloidal aggregates. We numerically generate fractal aggregates with a known structure, simulate the images that would be experimentally obtained from those aggregates, and analyze the simulated images using the proposed scattering model. Our results show that holographic microscopy accurately determines the fractal dimension (to within ~10%) when multiple scattering within the aggregates is negligible. They also suggest that holographic microscopy is useful because it probes the extinction cross section of the aggregates.