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1. Energetics of topographically designed Smectic-A oily streaks

   Missaoui, Amine ; Susser, Adam L. ; Aharoni, Hillel ; Rosenblatt, Charles ( May 2023 , Soft matter)

   A thin Smectic-A liquid crystal (LC) film is deposited on a polymer vinyl alcohol-coated substrate that had been scribed with a uniform easy axis pattern over a small square of dimensions side L < 85 um. Because of the small size of the patterned region facilitates material distribution to form either a hill (for a thin film) or divot (for a thick film) above the scribed square, which that exhibits an oily streak (OS) texture. Optical profilometry measurements vs. film thickness suggest that the OS structure aims to adopt a preferred thickness z0 that depends on the nature of the molecule, the temperature, and the surface tension at the air interface. We present a phenomenological model that estimates the energy cost of the OS layer as its thickness deviates from z0. 

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2. Laser Scribing of Photovoltaic Solar Thin Films: A Review

   https://doi.org/10.3390/jmmp7030094  

   Jamaatisomarin, Farzad ; Chen, Ruqi ; Hosseini-Zavareh, Sajed ; Lei, Shuting ( June 2023 , Journal of Manufacturing and Materials Processing)

   The development of thin-film photovoltaics has emerged as a promising solution to the global energy crisis within the field of solar cell technology. However, transitioning from laboratory scale to large-area solar cells requires precise and high-quality scribes to achieve the required voltage and reduce ohmic losses. Laser scribing has shown great potential in preserving efficiency by minimizing the drop in geometrical fill factor, resistive losses, and shunt formation. However, due to the laser induced photothermal effects, various defects can initiate and impact the quality of scribed grooves and weaken the module’s efficiency. In this regard, much research has been conducted to analyze the geometrical fill factor, surface integrity, and electrical performance of the laser scribes to reach higher power conversion efficiencies. This comprehensive review of laser scribing of photovoltaic solar thin films pivots on scribe quality and analyzes the critical factors and challenges affecting the efficiency and reliability of the scribing process. This review also covers the latest developments in using laser systems, parameters, and techniques for patterning various types of solar thin films to identify the optimized laser ablation condition. Furthermore, potential research directions for future investigations at improving the quality and performance of thin film laser scribing are suggested. 

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3. Foam film stratification studies probe intermicellar interactions

   https://doi.org/10.1073/pnas.2024805118  

   Ochoa, Chrystian ; Gao, Shang ; Srivastava, Samanvaya ; Sharma, Vivek ( June 2021 , Proceedings of the National Academy of Sciences)

   Ultrathin foam films containing supramolecular structures like micelles in bulk and adsorbed surfactant at the liquid–air interface undergo drainage via stratification. At a fixed surfactant concentration, the stepwise decrease in the average film thickness of a stratifying micellar film yields a characteristic step size that also describes the quantized thickness difference between coexisting thick–thin flat regions. Even though many published studies claim that step size equals intermicellar distance obtained using scattering from bulk solutions, we found no reports of a direct comparison between the two length scales. It is well established that step size is inversely proportional to the cubic root of surfactant concentration but cannot be estimated by adding micelle size to Debye length, as the latter is inversely proportional to the square root of surfactant concentration. In this contribution, we contrast the step size obtained from analysis of nanoscopic thickness variations and transitions in stratifying foam films using Interferometry Digital Imaging Optical Microscopy (IDIOM) protocols, that we developed, with the intermicellar distance obtained using small-angle X-ray scattering. We find that stratification driven by the confinement-induced layering of micelles within the liquid–air interfaces of a foam film provides a sensitive probe of non-DLVO (Derjaguin–Landau–Verwey–Overbeek) supramolecular oscillatory structural forces and micellar interactions.

    

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4. South Atlantic Transect: Variations in Oceanic Crustal Structure at 31°S

   https://doi.org/10.1029/2020GC009017  

   Christeson, G. L. ; Reece, R. S. ; Kardell, D. A. ; Estep, J. D. ; Fedotova, A. ; Goff, J. A. ( July 2020 , Geochemistry, Geophysics, Geosystems)

   We present an analysis of geophysical data acquired along a transect of 0–62 Ma crust located on the western flank of the Mid‐Atlantic Ridge at 31°S; all crust was formed at the same ridge segment. Crustal thickness, constrained by five wide‐angle profiles, has mean values of 5.6 km at 6.6 and 15.2 Ma, 7.0 km at 30.6 Ma, 5.5 km at 49.2 Ma, and 3.6 km at 61.2 Ma. Crustal thickness is uniform along each ridge‐parallel profile (standard deviations 0.1–0.3 km), indicating uniform along‐axis magmatic accretion over lateral distances of 40–60 km. The crustal structure of 61.2 Ma crust is not only anomalously thin compared to the other profiles but also contains regions with a linear velocity gradient from seafloor to Moho, which suggests that intense fracturing may extend to the base of the thin crust. Abyssal hill root‐mean‐square heights in the study region are 57–142 m and have an inverse correlation with spreading rate. These values are lower than the average root‐mean‐square height of 196 m elsewhere on the southern Mid‐Atlantic Ridge and indicate relatively high mantle temperatures in our study area. Unsedimented or lightly sedimented basement highs are prevalent at all ages; we argue that bottom currents scour the high topography, transporting sediment into adjacent basement lows. All drillsites planned for International Ocean Discovery Program Expeditions 390 and 393 are within 1–10 km of unsedimented or lightly sedimented basement highs, which should facilitate fluid flow and continued geochemical exchange between crust and seafloor.

    

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5. Ultrahigh evaporative heat transfer measured locally in submicron water films

   https://doi.org/10.1038/s41598-022-26182-2  

   Wang, Xiaoman ; Ghaffarizadeh, S. Arman ; He, Xiao ; McGaughey, Alan J. H. ; Malen, Jonathan A. ( December 2022 , Scientific Reports)

   Thin film evaporation is a widely-used thermal management solution for micro/nano-devices with high energy densities. Local measurements of the evaporation rate at a liquid-vapor interface, however, are limited. We present a continuous profile of the evaporation heat transfer coefficient ($$h_{\text {evap}}$$$h_{\text{evap}}$) in the submicron thin film region of a water meniscus obtained through local measurements interpreted by a machine learned surrogate of the physical system. Frequency domain thermoreflectance (FDTR), a non-contact laser-based method with micrometer lateral resolution, is used to induce and measure the meniscus evaporation. A neural network is then trained using finite element simulations to extract the$$h_{\text {evap}}$$$h_{\text{evap}}$profile from the FDTR data. For a substrate superheat of 20 K, the maximum$$h_{\text {evap}}$$$h_{\text{evap}}$is$$1.0_{-0.3}^{+0.5}$$$1.0_{-0.3}^{+0.5}$ MW/$$\text {m}^2$$${\text{m}}^2$-K at a film thickness of$$15_{-3}^{+29}$$${15}_{-3}^{+29}$ nm. This ultrahigh$$h_{\text {evap}}$$$h_{\text{evap}}$value is two orders of magnitude larger than the heat transfer coefficient for single-phase forced convection or evaporation from a bulk liquid. Under the assumption of constant wall temperature, our profiles of$$h_{\text {evap}}$$$h_{\text{evap}}$and meniscus thickness suggest that 62% of the heat transfer comes from the region lying 0.1–1 μm from the meniscus edge, whereas just 29% comes from the next 100 μm.

    

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