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A simple experimental method to estimate the power effectively absorbed by a plasma is presented. It relies on a thermal management study that is applied to the whole discharge system, providing the energy released by the plasma and lost by convection and radiation at the reactor walls. The methodology is illustrated in the case of H2 Electron Cyclotron Resonance microwave plasma. Nevertheless, this method can be extended to a variety of electrical discharge or feed gases. Using this method, an experimental coupling efficiency of ∼22 ± ∼8% was derived. In comparison, an analytical balance of the plasma power absorption yields a theoretical coupling efficiency of ∼28 ± ∼9%. [ABSTRACT FROM AUTHOR]

We study the effect of the addition of p- or n-type doping gases, trimethylboron (TMB) or phosphine, respectively, on cluster formation in the SiH4/H2 plasma used for the deposition of hydrogenated polymorphous silicon thin films. The formation of clusters is monitored using time-resolved measurements of the second harmonic of the radio frequency current J2. We show that the addition of PH3 does not change the cluster formation, while the addition of a small amount of trimethylboron strongly affects its charging behavior, preventing to some extent its agglomeration. The most ordered pm-Si:H thin films are obtained under conditions from which not only clusters but also larger silicon agglomerates are formed in the plasma and contribute to the deposition. The inhibiting role of TMB on the agglomeration and powder formation is evidenced by the smoothness of p-type films at high rates, as deduced from the sample surface topography obtained by atomic force microscopy measurements. [ABSTRACT FROM AUTHOR]

The formation of carbon nanoparticles in low pressure magnetized H2/CH4 and H2/C2H2 plasmas is investigated using infrared quantum cascade laser absorption, mass spectrometry, and electrostatic probe measurements. Results showed that dust formation is correlated to the presence of a significant amount of large positively charged hydrocarbon ions. Large negative ions or neutral hydrocarbon were not observed. These results, along with a qualitative comparison of diffusion and reaction characteristic, suggest that a positive ion may contribute to the growth of nanoparticles in hydrocarbon magnetized plasmas. [ABSTRACT FROM PUBLISHER]

This study presents the detailed characterization of a magnetron-based Ar-N2 plasma discharge used to sputter a liquid Ga target for the deposition of gallium nitride (GaN) thin films. By utilizing in situ diagnostic techniques including optical emission spectroscopy and microwave interferometry, we determine different temperatures (rotational and vibrational of N2 molecules, and electronic excitation of Ar atoms) and electron density, respectively. Beyond providing insights into fundamental plasma physics, our research establishes a significant correlation between gas-phase dynamics, particularly those of gallium atoms (flux and average energy at the substrate) and deposited GaN thin film properties (growth rate and crystalline fraction). These findings underscore the role of plasma conditions in enhancing thin film quality, highlighting the importance of plasma characterization in understanding and optimizing GaN thin film growth processes., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

Low-pressure plasma processes are routinely used to grow, functionalize or etch materials, and thanks to some of its unique attributes, plasma has become a major player for some applications such as microelectronics. Plasma processes are however still at a research level when it comes to the synthesis and functionalization of nanoparticles. Yet plasma processes can offer a particularly suitable solution to produce nanoparticles having very peculiar features since they enable to: (i) reach particle with a variety of chemical compositions, (ii) tune the size and density of the particle cloud by acting on the transport dynamics of neutral or charged particles through a convenient setting of the thermal gradients or the electric field topology in the reactor chamber and (iii) manipulate nanoparticles and deposit them directly onto a substrate, or codeposit them along with a continuous film to produce nanocomposites or (iv) use them as a template to produce 1D materials. In this article, we present an experimental investigation of nanoparticles synthesis and dynamics in low-pressure microwave plasmas by combining time-resolved and in-situ laser extinction and scattering diagnostics, QCL absorption spectroscopy, mass spectrometry, optical emission spectroscopy and SEM along with a particle transport model. We showed for the first time the thermophoresis-driven dynamic of particle cloud in electrodless microwave plasmas. We showed that this effect is linked to particular fluctuations in the plasma composition and results in the formation of a void region in the bulk of the plasma surrounded by a particle cloud in the peripherical post-discharge. We also reveals and analyze the kinetics of precursor dissociation and molecular growth that result in the observed nanoparticle nucleation., (© 2024. The Author(s).)

Epithelial, stem-cell derived organoids are ideal building blocks for tissue engineering, however, scalable and shape-controlled bio-assembly of epithelial organoids into larger and anatomical structures is yet to be achieved. Here, a robust organoid engineering approach, Multi-Organoid Patterning and Fusion (MOrPF), is presented to assemble individual airway organoids of different sizes into upscaled, scaffold-free airway tubes with predefined shapes. Multi-Organoid Aggregates (MOAs) undergo accelerated fusion in a matrix-depleted, free-floating environment, possess a continuous lumen, and maintain prescribed shapes without an exogenous scaffold interface. MOAs in the floating culture exhibit a well-defined three-stage process of inter-organoid surface integration, luminal material clearance, and lumina connection. The observed shape stability of patterned MOAs is confirmed by theoretical modelling based on organoid morphology and the physical forces involved in organoid fusion. Immunofluorescent characterization shows that fused MOA tubes possess an unstratified epithelium consisting mainly of tracheal basal stem cells. By generating large, shape-controllable organ tubes, MOrPF enables upscaled organoid engineering towards integrated organoid devices and structurally complex organ tubes., Competing Interests: The authors declare no conflict of interest., (© 2021 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Scalability and device integration have been prevailing issues limiting our ability in harnessing the potential of small-diameter conducting fibers. We report inflight fiber printing (iFP), a one-step process that integrates conducting fiber production and fiber-to-circuit connection. Inorganic (silver) or organic {PEDOT:PSS [poly(3,4-ethylenedioxythiophene) polystyrene sulfonate]} fibers with 1- to 3-μm diameters are fabricated, with the fiber arrays exhibiting more than 95% transmittance (350 to 750 nm). The high surface area-to-volume ratio, permissiveness, and transparency of the fiber arrays were exploited to construct sensing and optoelectronic architectures. We show the PEDOT:PSS fibers as a cell-interfaced impedimetric sensor, a three-dimensional (3D) moisture flow sensor, and noncontact, wearable/portable respiratory sensors. The capability to design suspended fibers, networks of homo cross-junctions and hetero cross-junctions, and coupling iFP fibers with 3D-printed parts paves the way to additive manufacturing of fiber-based 3D devices with multilatitude functions and superior spatiotemporal resolution, beyond conventional film-based device architectures., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

Freely suspended nanofibers, such as spider silk, harnessing their small diameter (sub-micrometer) and spanning fiber morphology, behave as a nonresonating acoustic sensor. The associated sensing characteristics, departing from conventional resonant acoustic sensors, could be of tremendous interest for the development of high sensitivity, broadband audible sensors for applications in environmental monitoring, biomedical diagnostics, and internet-of-things. Herein, a low packing density, freely suspended nanofiber mesh with a piezoelectric active polymer is fabricated, demonstrating a self-powered acoustic sensing platform with broad sensitivity bandwidth covering 200-5000 Hz at hearing-safe sound pressure levels. Dynamic near-field electrospinning is developed to fabricate in situ poled poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) nanofiber mesh (average fiber diameter ≈307 nm), exhibiting visible light transparency greater than 97%. With the ability to span the nanomesh across a suspension distance of 3 mm with minimized fiber stacking (≈18% fiber packing density), individual nanofibers can freely imitate the acoustic-driven fluctuation of airflow in a collective manner, where piezoelectricity is harvested at two-terminal electrodes for direct signal collection. Applications of the nanofiber mesh in music recording with good signal fidelity are demonstrated., (© 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)