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1. Reduced Biofilm Formation at the Air–Liquid–Solid Interface via Introduction of Surfactants

   https://doi.org/10.1021/acsbiomaterials.0c01691  

   Chen, Pengyu; Lang, Jiayan; Donadt, Trevor; Yu, Zichen; Yang, Rong (March 2021, ACS Biomaterials Science & Engineering)

   null (Ed.)

   Reduced biofilm formation is highly desirable in applications ranging from transportation to separations and healthcare. Biofilms often form at the three-phase interface where air, liquid, and solid coexist due to the close proximity to nutrients and oxygen. Reducing biofilm formation at the triple interface presents challenges because of the conflicting requirements for hydrophobicity at the air−solid interface (for selfcleaning properties) and for hydrophilicity at the liquid−solid interface (for reduced foulant adhesion). Meeting those needs simultaneously likely entails a dynamic surface, capable of shifting the surface energy landscape in response to wetting conditions and thus enabling hydrophobicity in air and hydrophilicity in water. Here, we designed a facile approach to render existing surfaces resistant to biofilm formation at the triple interface. By adding trace amounts (∼0.1 mM) of surfactants, biofilm formation of Pseudomonas aeruginosa (known to form biofilm at the triple interface) was reduced on all surfaces tested, ranging from hydrophilic to hydrophobic, polar to nonpolar. That reduced fouling was not a result of the known antimicrobial effects. Instead, it was attributed to the surface-adsorbed surfactants that dynamically control surface energy at the triple interface. To further understand the effect of surfactant−surface interactions on biofilm reduction, we systematically varied the surfactant charge type and surface properties (surface energy and charge). Electrostatic interactions between surfactants and surfaces were identified as an influential factor when predicting the relative fouling reduction upon introduction of surfactants. Nevertheless, biofilm formation was reduced even on the charge-neutral, fluorinated surface made of poly(1H, 1H, 2H, 2H-perfluorodecyl acrylate) by more than 2-fold simply via adding 0.2 mM dodecyl trimethylammonium chloride or 0.3 mM sodium dodecyl sulfate. Given its robustness, this strategy is broadly applicable for reducing fouling on existing surfaces, which in turn improves the cost-effectiveness of membrane separations and mitigates contaminations and nosocomial infections in healthcare. 

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2. Amphiphilic Polymer Thin Films with Enhanced Resistance to Biofilm Formation at the Solid–Liquid–Air Interface

   https://doi.org/10.1002/admi.202001791  

   Donadt, Trevor_B; Yang, Rong (January 2021, Advanced Materials Interfaces)

   Abstract Biofouling at the solid–liquid–air interface poses a serious threat to public health and environmental sustainability. Despite the variety of antifouling materials developed, few have proven to resist fouling at the three‐phase contact line. In fact, antifouling at the liquid–solid interface and the air–solid interface call for opposite surface properties—hydrophilic for the former and hydrophobic for the latter. By devising a new design strategy, one that maximizes the mismatch of surface energies of comonomers for dynamic chain reorientation at the three‐phase contact line, an antifouling amphiphilic copolymer is obtained. The novel amphiphilic copolymer reduces the formation of biofilms byPseudomonas aeruginosaand outperforms a zwitterionic polymer, the current leading antifouling chemistry. The copolymer is synthesized using initiated chemical vapor deposition (iCVD), which leads to molecular‐level heterogeneities composed of zwitterionic and fluorinated moieties by avoiding undesirable surface tension effects. Atomic force microscopy, x‐ray diffractometry, and Fourier transform infrared spectroscopy confirm the copolymer's amphiphilicity and lack of microphase separation. Scanning electron microscopy provides visual confirmation of the diminished biofilm growth. The versatile iCVD technique is amenable to a range of substrates and enables the application of this new material to food processing, healthcare, and underwater performance. 

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3. DiSCoVeR: a materials discovery screening tool for high performance, unique chemical compositions

   https://doi.org/10.1039/D1DD00028D  

   Baird, Sterling G.; Diep, Tran Q.; Sparks, Taylor D. (February 2022, Digital Discovery)

   We present Descending from Stochastic Clustering Variance Regression (DiSCoVeR) (https://www.github.com/sparks-baird/mat_discover), a Python tool for identifying and assessing high-performing, chemically unique compositions relative to existing compounds using a combination of a chemical distance metric, density-aware dimensionality reduction, clustering, and a regression model. In this work, we create pairwise distance matrices between compounds via Element Mover's Distance (ElMD) and use these to create 2D density-aware embeddings for chemical compositions via Density-preserving Uniform Manifold Approximation and Projection (DensMAP). Because ElMD assigns distances between compounds that are more chemically intuitive than Euclidean-based distances, the compounds can then be clustered into chemically homogeneous clusters via Hierarchical Density-based Spatial Clustering of Applications with Noise (HDBSCAN*). In combination with performance predictions via Compositionally-Restricted Attention-Based Network (CrabNet), we introduce several new metrics for materials discovery and validate DiSCoVeR on Materials Project bulk moduli using compound-wise and cluster-wise validation methods. We visualize these via multi-objective Pareto front plots and assign a weighted score to each composition that encompasses the trade-off between performance and density-based chemical uniqueness. In addition to density-based metrics, we explore an additional uniqueness proxy related to property gradients in DensMAP space. As a validation study, we use DiSCoVeR to screen materials for both performance and uniqueness to extrapolate to new chemical spaces. Top-10 rankings are provided for the compound-wise density and property gradient uniqueness proxies. Top-ranked compounds can be further curated via literature searches, physics-based simulations, and/or experimental synthesis. Finally, we compare DiSCoVeR against the naive baseline of random search for several parameter combinations in an adaptive design scheme. To our knowledge, this is the first time automated screening has been performed with explicit emphasis on discovering high-performing, novel materials. 

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4. Barometers Behaving Badly II: a Critical Evaluation of Cpx-Only and Cpx-Liq Thermobarometry in Variably-Hydrous Arc Magmas

   https://doi.org/10.1093/petrology/egad050  

   Wieser, Penny E; Kent, Adam_J R; Till, Christy B (August 2023, Journal of Petrology)

   The chemistry of erupted clinopyroxene crystals (±equilibrium liquids) have been widely used to deduce the pressures and temperatures of magma storage in volcanic arcs. However, the large number of different equations parameterizing the relationship between mineral and melt compositions and intensive variables such as pressure and temperature yield vastly different results, with implications for our interpretation of magma storage conditions. We use a new test dataset composed of the average Clinopyroxene-Liquid (Cpx-Liq) compositions from N = 543 variably hydrous experiments at crustal conditions (1 bar to 17 kbar) to assess the performance of different thermobarometers and identify the most accurate and precise expressions for application to subduction zone magmas. First, we assess different equilibrium tests, finding that comparing the measured and predicted Enstatite-Ferrosillite and KD (using Fet in both phases) are the most useful tests in arc magmas, whereas CaTs, CaTi and Jd tests have limited utility. We then apply further quality filters based on cation sums (3.95–4.05), number of analyses (N > 5) and the presence of reported H2O data in the quenched experimental glass (hereafter ‘liquid’) to obtain a filtered dataset (N = 214). We use this filtered dataset to compare calculated versus experimental pressures and temperatures for different combinations of thermobarometers. A number of Cpx-Liq thermometers perform very well when liquid H2O contents are known, although the Cpx composition contributes little to the calculated temperature relative to the liquid composition. Most Cpx-only thermometers perform very badly, greatly overestimating temperatures for hydrous experiments. These two findings demonstrate that the Cpx chemistry alone holds very little temperature information in hydrous systems. Most Cpx-Liq and Cpx-only barometers show similar performance to one another (mostly yielding root mean square errors [RMSEs] of 2–3.5 kbar), although the best Cpx-only barometers currently outperform the best Cpx-Liq barometers. We also assess the sensitivity of different equations to melt H2O contents, which are poorly constrained in many natural systems. Overall, this work demonstrates that Cpx-based barometry on individual Cpx only provides sufficient resolution to distinguish broad storage regions in continental arcs (e.g. upper, mid, lower crust). Significant averaging of Cpx compositions from experiments reported at similar pressures can reduce RMSEs to ~1.3–1.9 kbar. We hope our findings motivate the substantial amount of experimental and analytical work that is required to obtain precise and accurate estimates of magma storage depths from Cpx ± Liq equilibrium in volcanic arcs. 

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5. Purification and Fractionation of Lignin via ALPHA: Liquid–Liquid Equilibrium for the Lignin–Acetic Acid–Water System

   https://doi.org/10.1002/cssc.202300989  

   Agede, Oreoluwa; Thies, Mark_C (October 2023, ChemSusChem)

   Abstract In order to effectively practice the Aqueous Lignin Purification with Hot Agents (ALPHA) process for lignin purification and fractionation, the temperatures and feed compositions where regions of liquid–liquid equilibrium (LLE) exist must be identified. To this end, pseudo‐ternary phase diagrams for the lignin–acetic acid–water system were mapped out at 45–95 °C and various solvent: feed lignin mass ratios (S : F). For a given temperature, the accompanying SL (solid–liquid), SLL (solid–liquid–liquid), and one‐phase regions were also located. For the first time, ALPHA using acetic acid (AcOH)–water solution was applied to a lignin recovered via the commercial LignoBoost process. In addition to determining tie‐line compositions for the two regions of LLE that were discovered, the distribution of lignin and key impurities (the latter can negatively impact lignin performance for materials applications) between the two liquid phases was also measured. As a representative example, lignin isolated in the lignin‐rich phase was reduced 7x in metals and 4x in polysaccharides by using ALPHA with a feed solvent composition of 50–55 % AcOH and an S : F of 6 : 1, with said lignin being obtained at a yield of 50–70 % of the feed lignin and having a molecular weight triple that of the feed. 

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