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A paper by our group, in collaboration with David Srolovitz’s group at UPenn, was recently published in Nano Letters [view pdf or view at publisher]. A multiscale modeling framework was formulated to describe structural transformations in transition metal dichalcogenide (TMD) monolayers. It was demonstrated that application of strain can be used to control the morphology and mechanical response of these elastically bendable 2D materials in order to generate functionally patterned domains of the metallic/semimetallic T’ phase. This enables dynamically programmable 2D materials with locally conducting regions that can be “drawn” in real time.

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A paper by Mikko was recently published in Biophysical Journal [view pdf or view at publisher]. It is shown that fluctuation-induced interactions of compositional domains in multicomponent lipid bilayer membranes provide a means for co-localization of domains in the two leaflets. Spatial variations in membrane bending rigidity are demonstrated to lead to an attractive interleaflet coupling that is robust against membrane tension and
substrate interactions.

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Research from our group, in collaboration with the groups of Jared Toettcher and Cliff Brangwynne, was recently published in a Cell paper [view pdf or view at publisher]. Light-dependent triggering of protein association allows selective temporal and spatial control of droplet and gel formation aimed at understanding the different forms of membrane-less bodies and fibrillar structures within cells. More information can also be found in this Princeton news article.

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Ryan presented a poster titled “Simulating Fracture in SOFC Anode Materials” at the Fifth Annual Princeton E-ffiliates Partnership Meeting. His poster features a phase-field model of brittle fracture that captures the stresses induced from oxidation in fuel cells and the resulting fracture events. Check out the poster!

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Dr. Joel Berry has finished his postdoc in our group and will now join Prof. David Srolovitz’s group at UPenn as a postdoc. First-year MAE graduate student Yang Xia has joined our group. Best wishes to Joel in his new position, and welcome to Yang!

A simulation study of twisted crystal growth in organic thin films has recently been published in Physical Review E [view pdf or view at publisher]. We developed a phase-field model that energetically favors twisting of the 3D crystalline orientation about and along particular axes, allowing us to simulate a variety of morphologies, including banded spherulites, curved dendrites, and “s”-shaped or “c”-shaped needle crystals. In curved dendrites, we find that the twisting rate affects not only the morphology but also the kinetics of crystallization.

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Droplet Growth SimulationC. Elegans Nuclear Bodies

Our investigation of the assembly dynamics of membraneless biological organelles was published this week in the online Early Edition of Proceedings of the National Academy of Sciences [view pdf or view at publisher]. In collaboration with Stephanie Weber, Nilesh Vaidya, and Cliff Brangwynne from the Department of Chemical and Biological Engineering, we have shown that the assembly dynamics of liquid-phase nuclear bodies (condensed droplets rich in RNA and protein) in C. Elegans embryos can be explained by classical models of phase separation and coarsening long associated with nonliving condensed matter – namely Brownian coalescence and, to a lesser degree, Ostwald ripening. Our findings also indicate that highly nonequilibrium biological activity such as rRNA transcription, rather than fundamentally altering the passive phase separation mechanisms, can act to locally modulate the thermodynamic parameters governing phase separation, thus locally fine tuning organelle size and stability in response to developmental or environmental conditions.

 

capillary_effects_diagramA study of capillary effects in channel-guided crystallization of organic thin films was recently published in APL Materials [view pdf or view at publisher]. An analytical expression was derived for the growth velocity of crystallization guided along a channel defined by differential growth rates. The equation was validated with phase-field simulations and then fit to experimental data for solvent vapor annealed thin films of TES ADT, which yielded the ratio of interfacial energy to bulk thermodynamic driving force and the minimum feature size that can be patterned with this technique.

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A study of bulk metallic glass systems from the group has recently been published in the journal “Modelling and Simulation in Materials Science and Engineering.” This work addresses the problem of catastrophic failure via intense plastic strain localization. Employing a non-linear continuum model, we show that the precipitation of crystalline particles yields microstructures that delay the propagation of incipient shear bands and ultimately result in improved ductility characteristics. See the research page for more information on this topic.

At this year’s MAE research day, an annual event where graduate students in the department share their research, Alta represented the materials area and won first place for her talk on modeling crystallization in organic thin films. At the MAE welcome back BBQ, Alta was also recognized for receiving the Larisse Rosentweig Klein Memorial Award, which is presented to a post-general female graduate student who shows outstanding promise in graduate research.
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