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1. Dual-tracer laser-induced fluorescence thermometry for understanding bubble growth during nucleate boiling on oriented surfaces

   https://doi.org/10.1016/j.ijheatmasstransfer.2024.125517  

   Ghazvini, Mahyar; Hafez, Mazen; Pena, Cristian; Mandin, Philippe; Inguanta, Rosalinda; Kim, Myeongsub (August 2024, International Journal of Heat and Mass Transfer)

   Nucleate boiling is perhaps one of the most efficient cooling methodologies due to its large heat flux with a relatively low superheat. Nucleate boiling often occurs on surfaces oriented at different angles; therefore, understanding the behavior of bubble growth on various surface orientations is of importance. Despite significant advancement, numerous questions remain regarding the fundamentals of bubble growth mechanisms on oriented surfaces, a major source of enhanced heat dissipation. This work aims to accurately measure three-dimensional (3D), space- and time-resolved, local liquid temperature distributions surrounding a growing bubble on oriented surfaces that quantify the heat transfer from the superheated liquid layer during bubble growth. The dual tracer laser-induced fluorescence thermometry technique combined with high-speed imaging captures transient 2D temperature distributions within a 0.3 ºC accuracy at a 30 μm resolution. The results show that the temperature close to the heated surface and bubble interface exhibits an acute transient behavior at the time of bubble departure, and the growing bubble works as a pump to remove heat from the surface with a temperature difference of up to 10 °C during its growth and departure. The experimental results are compared with data available in the literature to validate the accuracy of the technique. It was found that the heat transfer coefficient close to the bubble interface and heater is approximately 1.3 times higher than the heat transfer coefficient in the bulk liquid. 

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2. Isoflavonoid-Antibiotic Thin Films Fabricated by MAPLE with Improved Resistance to Microbial Colonization

   https://doi.org/10.3390/molecules26123634  

   Grumezescu, Valentina; Negut, Irina; Cristescu, Rodica; Grumezescu, Alexandru Mihai; Holban, Alina Maria; Iordache, Florin; Chifiriuc, Mariana Carmen; Narayan, Roger J.; Chrisey, Douglas B. (June 2021, Molecules)

   Staphylococcus aureus (Gram-positive) and Pseudomonas aeruginosa (Gram-negative) bacteria represent major infectious threats in the hospital environment due to their wide distribution, opportunistic behavior, and increasing antibiotic resistance. This study reports on the deposition of polyvinylpyrrolidone/antibiotic/isoflavonoid thin films by the matrix-assisted pulsed laser evaporation (MAPLE) method as anti-adhesion barrier coatings, on biomedical surfaces for improved resistance to microbial colonization. The thin films were characterized by Fourier transform infrared spectroscopy, infrared microscopy, and scanning electron microscopy. In vitro biological assay tests were performed to evaluate the influence of the thin films on the development of biofilms formed by Gram-positive and Gram-negative bacterial strains. In vitro biocompatibility tests were assessed on human endothelial cells examined for up to five days of incubation, via qualitative and quantitative methods. The results of this study revealed that the laser-fabricated coatings are biocompatible and resistant to microbial colonization and biofilm formation, making them successful candidates for biomedical devices and contact surfaces that would otherwise be amenable to contact transmission. 

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3. Thermophysical properties of 1D materials: transient characterization down to atomic level

   https://doi.org/10.52396/JUSTC-2023-0098  

   Karamati, Amin; Xu, Shen; Lin, Huan; Rahbar, Mahya; Wang, Xinwei (January 2023, JUSTC)

   The thermophysical properties of 1D micro/nanoscale materials could differ significantly from those of their bulk counterparts due to intensive energy carrier scattering by structures. This work provides an in-depth review of cutting-edge techniques employed for transient characterization of thermophysical properties at the micro/nanoscale scale. In terms of transient excitation, step Joule heating, step laser heating, pulsed laser heating, and frequency domain amplitude-modulated laser heating are covered. For thermal probing, electrical and Raman scattering-based physical principles are used. These techniques enable the measurement of thermal conductivity, thermal diffusivity, and specific heat from the sub-mm level down to the atomic level (single-atom thickness). This review emphasizes the advantages of these techniques over steady state techniques and their physics, challenges, and potential applications, highlighting their significance in unraveling the intricate thermal transport phenomena to the atomic level of 1D materials. 

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4. Ramifications of Pulsed Laser Deposition Growth Temperature on BaHfO₃ and Y₂O₃ Doped Y-Ba-Cu-O Thin Films' Microstructure & Performance

   https://doi.org/10.1109/TASC.2021.3068112  

   Sebastian, Mary Ann; Ebbing, Charles R.; Wang, Han; Wang, Haiyan; Bibek, Gautam; Wu, Judy; Haugan, Timothy (January 2021, IEEE Transactions on Applied Superconductivity)

   null (Ed.)

   Deposition temperature is an important parameter to control in pulsed laser deposition of thin films, as it affects the ad-atom mobility and diffusion in regards to film growth. Increased growth temperature can also result in increased stacking fault densities in YBa2Cu3O7- (YBCO) films. This research investigates the influence of deposition temperature on the critical current density, critical temperature, and the microstructure of YBCO thin films double doped with BaHfO3 and Y2O3. A KrF excimer laser was used to produce thin films of YBCO doped with 4 vol.% BaHfO3 and 3 vol. % Y2O3 on LaAlO3 (LAO) substrates at various deposition temperatures from 790 - 825. The growth temperature influence on the flux pinning landscape and Jc (H,T,) properties (T = 5 - 77K, H = 0 - 9T, = 0 -180) of these films will be presented. 

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5. Successful Release of Voriconazole and Flavonoids from MAPLE Deposited Bioactive Surfaces

   https://doi.org/10.3390/app9040786  

   Negut, Irina; Visan, Anita; Popescu, Camelia; Cristescu, Rodica; Ficai, Anton; Grumezescu, Alexandru; Chifiriuc, Mariana; Boehm, Ryan; Yamaleyeva, Dina; Taylor, Michael; et al (February 2019, Applied Sciences)

   We explored the potential of biomimetic thin films fabricated by means of matrix-assisted pulsed laser evaporation (MAPLE) for releasing combinations of active substances represented by flavonoids (quercetin dihydrate and resveratrol) and antifungal compounds (amphotericin B and voriconazole) embedded in a polyvinylpyrrolidone biopolymer; the antifungal activity of the film components was evaluated using in vitro microbiological assays. Thin films were deposited using a pulsed KrF* excimer laser source which were structurally characterized using atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). High-quality thin films with chemical structures similar to dropcast ones were created using an optimum laser fluence of ~80 mJ/cm2. Bioactive substances were included within the polymer thin films using the MAPLE technique. The results of the in vitro microbiology assay, which utilized a modified disk diffusion approach and were performed using two fungal strains (Candida albicans American Type Culture Collection (ATCC) 90028 and Candida parapsilosis American Type Culture Collection (ATCC) 22019), revealed that voriconazole was released in an active form from the polyvinylpyrrolidone matrix. The results of this study show that the MAPLE-deposited bioactive thin films have a promising potential for use in designing combination devices, such as drug delivery devices, and medical device surfaces with antifungal activity. 

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