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1. In situ and ex situ processes for synthesizing metal multilayers with electronically conductive interfaces

   https://doi.org/10.1063/5.0084573  

   Angeles, Frank; Shi, Xinping; Wilson, Richard B. (June 2022, Journal of Applied Physics)

   A number of technological applications and scientific experiments require processes for preparing metal multilayers with electronically and thermally conductive interfaces. We investigate how in situ vs ex situ synthesis processes affect the thermal conductance of metal/metal interfaces. We use time-domain thermoreflectance experiments to study thermal transport in Au/Fe, Al/Cu, and Cu/Pt bilayer samples. We quantify the effect of exposing the bottom metal layer to an ambient environment prior to deposition of the top metal layer. We observe that for Au/Fe, exposure of the Fe layer to air before depositing the top Au layer significantly impedes interfacial electronic currents. Exposing Cu to air prior to depositing an Al layer effectively eliminates interfacial electronic heat currents between the two metal layers. Exposure to air appears to have no effect on interfacial transport in the Cu/Pt system. Finally, we show that a short RF sputter etch of the bottom layer surface is sufficient to ensure a thermally and electronically conductive metal/metal interface in all materials we study. We analyze our results with a two-temperature model and bound the electronic interface conductance for the nine samples we study. Our findings have applications for thin-film synthesis and advance fundamental understanding of electronic thermal conductance at different types of interfaces between metals. 

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2. In situ monitoring of PISA morphologies

   https://doi.org/10.1039/d1py00239b  

   Rho, Julia Y.; Scheutz, Georg M.; Häkkinen, Satu; Garrison, John B.; Song, Qiao; Yang, Jie; Richardson, Robert; Perrier, Sébastien; Sumerlin, Brent S. (July 2021, Polymer Chemistry)

   Polymerization-induced self-assembly (PISA) is a facile method to obtain block copolymer aggregates with defined morphologies. However, the transitions between these morphologies have been difficult to monitor directly in real-time during the polymerization. Herein, we describe a straightforward and readily accessible in situ method to monitor the evolution of nanostructure via changes in internal hydrophobicity during the PISA process using a polymer-tethered pyrene fluorescent probe. We were able to correlate morphological transitions with changes of the pyrene emission and gain unprecedented insight into the evolution of core hydrophobicity during PISA. 

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3. Nonlinear memristor model with exact solution allows for ex situ reservoir computing training and in situ inference

   https://doi.org/10.1039/D4NR03439B  

   Armendarez, Nicholas; Hasan, Md Sakib; Najem, Joseph (January 2025, Nanoscale)

   A generalized logistic differential equation model of biomolecular memristors improves the tuning of hyperparameters of parallel-memristor physical reservoir computing systems by enablingex situtraining. 

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4. Ex Situ Gaseous Reagent for Multicomponent Amine Bioconjugation

   https://doi.org/10.1021/acs.orglett.4c02246  

   Ding, Yuxuan; Pedersen, Simon S; Wang, Yixian; Xiao, Han; Ball, Zachary T (July 2024, Organic Letters)

   We report a minimalist gaseous sulfonyl-chloride-derived reagent for multicomponent bioconjugation with amine, phenol, or aniline reagents to afford urea or carbamate products. With the utilization of a gas-phase reagent for a reaction mediated by metal ions, a variety of biologically relevant molecules, such as saccharide, poly(ethylene glycol), fluorophore, and affinity tag, can be efficiently cross-linked to the N terminus or lysine side-chain amines on natural polypeptides or proteins. 

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5. In situ / operando synchrotron x-ray studies of metal additive manufacturing

   https://doi.org/10.1557/mrs.2020.275  

   Sun, Tao; Tan, Wenda; Chen, Lianyi; Rollett, Anthony (November 2020, MRS Bulletin)

   null (Ed.)

   Additive manufacturing (AM) comprises a group of transformative technologies that are likely to revolutionize manufacturing. In particular, laser-based metal AM techniques can not only fabricate parts with extreme complexity, but also provide innovative means for designing and processing new metallic systems. However, there are still several technical barriers that constrain metal AM. Overcoming these barriers requires a better understanding of the physics underlying the complex and dynamic laser–metal interaction at the heart of many AM processes. This article briefly describes the state of the art of in situ / operando synchrotron x-ray imaging and diffraction for studying metal AM, mostly the laser powder-bed fusion process. It highlights the immediate impact of operando synchrotron studies on the advancement of AM technologies, and presents future research challenges and opportunities. 

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