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Professor Ruiz Pestana’s paper in ACS Nano offers insight into how and how fast water nanodroplets evaporate on heated surfaces, and on how their behavior strikingly departs from predictions of well-established macroscopic theories of evaporation

While experiments and continuum models have provided a relatively good understanding of the evaporation of macroscopic water droplets, elucidating how sessile nanodroplets evaporate is an open question critical for advancing nanotechnological applications where nanodroplets can play an essential role. Here, using molecular dynamics simulations, we find that evaporating nanodroplets, in contrast to their macroscopic counterparts, are not always in thermal equilibrium with the substrate and that the vapor concentration on the nanodroplet surface does not reach a steady state. As a result, the evaporative behavior of nanodroplets is significantly different. Regardless of hydrophobicity, nanodroplets do not follow conventional evaporation modes but instead exhibit dynamic wetting behavior characterized by huge, non-equilibrium, isovolumetric fluctuations in the contact angle and contact radius. For hydrophilic nanodroplets, the evaporation rate, controlled by the vapor concentration, decays exponentially over time. Hydrophobic nanodroplets follow stretched exponential kinetics arising from the slower thermalization with the substrate. The evaporative half-lifetime of the nanodroplets is directly related to the thermalization time scale and therefore increases monotonically with the hydrophobicity of the substrate. Finally, the evaporative flux profile along the nanodroplet surface is highly nonuniform but does not diverge at the contact line as the macroscopic continuum models predict.

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James Coakley, Assistant Professor of Mechanical and Aeronautic Engineering, received the National Science Foundation (NSF)’s most prestigious grant to faculty members starting their academic careers, Early Career Development Program (CAREER) award.

This grant, titled “CAREER: Precipitation Pathways and Deformation Micromechanisms of Refractory Superalloys (RSAs),” will be used to support Prof. Coakley’s research on refractory superalloys, a new family of structural materials that possess a promising combination of high strength and plasticity at room temperature and higher temperatures.

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Researchers capture how materials break apart following an extreme shock

University of Miami Professor James Coakley and his collaborators’ groundbreaking study to understand fundamental processes in materials during extremely rapid failure, published in Science Advances, is showcased on the SLAC National Accelerator Laboratory Site.

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Interdisciplinary Research at the U on Multiscale Study of Sustainable Infrastructure Materials by Professors Prannoy Suraneni and Luis Ruiz Pestana Funded By National Science Foundation.

The interdisciplinary research proposal by Civil, Architectural, and Environmental Engineering (CAEE) Professors Prannoy Suraneni and Luis Ruiz Pestana at the University of Miami was selected for a National Science Foundation (NSF) grant to study multiscale approaches to develop next-generation sustainable infrastructure materials. Together, this team brings the expertise of multiscale stimulations and dissolution experiments and reactivity tests to integrate knowledge across all the relevant time and length scales as required for bridging the gap between current molecular and macroscale understanding of glass reactivity as a function of its composition. The NSF grant (#2101961) is titled “Multiscale study of dissolution and reactivity of calcium aluminosilicate glasses: Toward the rational design of low-carbon cement substitutes.” By developing such fundamental, multiscale understanding of the mechanisms that govern the dissolution and reactivity of calcium aluminosilicate glasses, this team aims to reduce anthropogenic carbon emissions. These glasses are the main reactive phases of supplementary cementitious materials (SCMs), low-carbon replacements for cements in concrete. The results of this study promise to enable the rational selection of highly reactive SCM formulations to achieve unprecedented levels of OPC replacement in concrete, which will significantly help reduce the carbon footprint associated with the concrete industry. In addition to the proposed research, their educational outreach activities, in collaboration with Dream in Green, aim to educate students on the importance of sustainable infrastructure materials and the key role that science and engineering play on their development. Through those activities, they also aim to provide role models to students, in particular to women and other underrepresented minorities in STEM.