Charged particles grow to stable planetesimal progenitors
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Optical sorting: past, present and future
Optical sorting combines optical tweezers with diverse techniques, including optical spectrum, artificial intelligence (AI) and immunoassay, to endow unprecedented capabilities in particle sorting. In comparison to other methods such as microfluidics, acoustics and electrophoresis, optical sorting offers appreciable advantages in nanoscale precision, high resolution, non-invasiveness, and is becoming increasingly indispensable in fields of biophysics, chemistry, and materials science. This review aims to offer a comprehensive overview of the history, development, and perspectives of various optical sorting techniques, categorised as passive and active sorting methods. To begin, we elucidate the fundamental physics and attributes of both conventional and exotic optical forces. We then explore sorting capabilities of active optical sorting, which fuses optical tweezers with a diversity of techniques, including Raman spectroscopy and machine learning. Afterwards, we reveal the essential roles played by deterministic light fields, configured with lens systems or metasurfaces, in the passive sorting of particles based on their varying sizes and shapes, sorting resolutions and speeds. We conclude with our vision of the most promising and futuristic directions, including AI-facilitated ultrafast and bio-morphology-selective sorting. It can be envisioned that optical sorting will inevitably become a revolutionary tool in scientific research and practical biomedical applications.
Systematic quantification of hydrogen in pipeline steel by atom probe tomography after ambient charging and transfer
Atom probe tomography (APT) is a promising tool to measure the atomic-scale distribution of hydrogen in solid matter for the assessment of hydrogen embrittlement susceptibility of materials. However, the accuracy of such measurements resulting from ambient charging and transfer experiments needs to be established. In this work, APT quantification of hydrogen (H) and deuterium (D) in a typical X65 pipeline steel has been determined after ambient charging and transfer to ascertain the contribution of artifacts to the measured H/D signal. A series of experimental workflows related to sample preparation (electropolishing, focussed ion beam) and electrochemical charging conditions (different electrolytes and charging potentials) were explored for H/D measurement using APT. The results show that APT can be used to measure charged H/D with statistical confidence after ambient charging and transfer, that hydrogen ingress occurs during electropolishing, and using a more negative charging potential will introduce more H/D into the material.
Global atmospheric distribution of microplastics with evidence of low oceanic emissions
Recent investigations based on sea–air transfer physical mechanistic studies suggest that the global ocean’s contribution to atmospheric microplastic emissions is significantly lower (four orders of magnitude) than previously estimated. However, no atmospheric models or observations have yet validated this lower emission flux, leaving the analysis without adequate validation and practical significance. Here, we provide quantitative estimates of the global atmospheric microplastic budget based on this reduced oceanic flux. Our model aligns well with observed atmospheric microplastic concentrations and suggests that the ocean functions more as a sink than a source, contributing only ~0.008% of global emissions but accounting for ~15% of total deposition. This challenges the previous view of the ocean as the primary atmospheric microplastic source, urging a reassessment of pollution mitigation strategies.
Feedback effect of the size of mineral particles on the molecular mechanisms employed by Caballeronia mineralivorans PML1(12) to weather minerals
Mineral dissolution by bacteria is thought to depend on mineral properties, solution chemistry, and the carbon sources metabolized. To investigate whether mineral particle size could impact the effectiveness of weathering and the molecular mechanisms employed by bacteria, the strain Caballeronia mineralivorans PML1(12) was considered. Through microcosm and kinetic experiments, we quantified changes in biotite dissolution, bacterial growth, siderophore biosynthesis, and acidification. The use of different solution chemistries, carbon sources, and particle sizes (from <20 to 500 µm) allowed us to decipher the relative role of acidification- and chelation-driven mineral weathering by bacteria. Results revealed a faster dissolution for smaller particles (<100 µm) that strongly affected both solution chemistry and bacterial physiology, while larger particles (>100 µm) showed a slower and steady dissolution with minimal impact on bacterial processes. These findings underscore the influence and feedback effects of particle size on the dynamics of dissolution and the mechanisms employed by bacteria.
Absorption enhancement and shielding effect of brown organic coating on black carbon aerosols
This study explores how the mixing structures and coating compositions of black carbon (BC) particles influence their light absorption, focusing on liquid-liquid phase separation (LLPS), which separates organic and inorganic phases and redistributes BC from the inorganic core (Icore) to the organic coating (Ocoating). Using transmission electron microscopy and 3D-modeling, we found that the BC core’s position significantly impacts its light absorption. A BC core embedded within the Icore shows stronger light absorption at wavelengths below 600 nm compared to the same core in the Ocoating. When Ocoating is considered as brown carbon (BrC), it reduces BC core’s light absorption at 350 nm due to shielding effect, but its overall impact on the entire BC particle is minimal (–3.0% ± 1.6%). The result indicates that in LLPS particles, the BrC coating primarily enhances light absorption, emphasizing the need to consider both mixing structures and coating compositions of BC in atmospheric models.
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