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Creators/Authors contains: "Qin, Jian"

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  1. Free, publicly-accessible full text available October 24, 2024
  2. Free, publicly-accessible full text available August 8, 2024
  3. Self-healing soft electronic and robotic devices can, like human skin, recover autonomously from damage. While current devices use a single type of dynamic polymer for all functional layers to ensure strong interlayer adhesion, this approach requires manual layer alignment. In this study, we used two dynamic polymers, which have immiscible backbones but identical dynamic bonds, to maintain interlayer adhesion while enabling autonomous realignment during healing. These dynamic polymers exhibit a weakly interpenetrating and adhesive interface, whose width is tunable. When multilayered polymer films are misaligned after damage, these structures autonomously realign during healing to minimize interfacial free energy. We fabricated devices with conductive, dielectric, and magnetic particles that functionally heal after damage, enabling thin-film pressure sensors, magnetically assembled soft robots, and underwater circuit assembly.

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    Free, publicly-accessible full text available June 2, 2024
  4. The induced surface charges appear to diverge when dielectric particles form close contacts. Resolving this singularity numerically is prohibitively expensive because high spatial resolution is needed. We show that the strength of this singularity is logarithmic in both inter-particle separation and dielectric permittivity. A regularization scheme is proposed to isolate this singularity, and to calculate the exact cohesive energy for clusters of contacting dielectric particles. The results indicate that polarization energy stabilizes clusters of open configurations when permittivity is high, in agreement with the behavior of conducting particles, but stabilizes the compact configurations when permittivity is low. 
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  5. null (Ed.)
  6. Abstract

    Electrochemical cells that utilize metals (e.g., lithium, sodium, zinc) as anodes are under intense investigation as they are projected to replace the current lithium‐ion batteries to serve as a more energy‐dense option for commercial applications. In addition, metal electrodes provide opportunities for fundamental research of different phenomena, such as ion transport and electrochemical kinetics, in the complex environment of reactive metal‐electrodeposition. In this work, computationally and experimentally the competing effects related to transport and kinetics during the metal electrodeposition process are examined. Using Brownian dynamics simulations, it is shown that slower deposition kinetics results in a more compact and uniform Li morphology. This finding is experimentally implemented by designing ion‐containing polymeric coatings on the electrodes that simultaneously provide pathways for lithium‐ion transport, while impeding the charge transfer (Li++ e→ Li) at heterogeneous surfaces. It is further shown that these ionic polymer interfaces can significantly extend the cell‐lifetime of a lithium metal battery in both ether‐based and carbonate‐based electrolytes. Through theoretical and experimental investigations, it is found that a low kinetic to transport rate ratio is a major factor in influencing the Li plating morphology. The plating morphology can be further fine‐tuned by increasing ionic conductivity.

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