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1. Translation of protein charge and hydrophilicity to materials surface properties using thermal treatment in fluorous media

   https://doi.org/10.1039/C7MH00933J  

   Wang, Li-Sheng; Gopalakrishnan, Sanjana; Lee, Yi-Wei; Zhu, Jiaxin; Nonnenmann, Stephen S.; Rotello, Vincent M. (January 2018, Materials Horizons)

   Protein-based materials provide an inherently biocompatible and sustainable platform for the generation of functional materials. Translating protein properties into protein films resistant to aqueous degradation is crucial for most applications such as tissue engineering and controlled drug delivery. Current methods to stabilize protein films use three main strategies: employing the relatively limited variety of naturally self-assembling proteins, using added cross-linkers or heat curing. While the cross-linking strategy generates functionally diverse structures, unreacted additives retained in cross-linked protein films can adversely affect their final behavior. Traditional heat curing results in hydrophobic surface and loss of protein inherent properties. We demonstrate here a scalable, additive-free, fluorous media assisted thermal treatment for the fabrication of stable, hydrophilic protein films. This approach is general in terms of protein building block, retaining much of their native structure and surface properties upon heating. We demonstrate the versatility of this strategy through fabrication of antifouling coatings on complex three-dimensional surfaces. The utility of these films as biomaterials is highlighted through the generation of highly biocompatible non-fouling surfaces and regulation of cellular adhesion through choice of protein precursor. 

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2. Temporal Changes in Thirdhand Cigarette Smoke Film Composition and Oxidation of Co-existing Surface Film Chemicals

   https://doi.org/10.1039/D3EA00142C  

   Hurlock, April M; Collins, Douglas B (January 2024, Environmental Science: Atmospheres)

   The composition of air-exposed surfaces can have a strong impact on air quality and chemical exposure in the indoor environment. Third hand smoke (THS), which includes surface-deposited cigarette smoke residue along with the collection of gases evolved from such residues, is becoming increasingly recognized as an important source of long-term tobacco smoke exposure. While studies have described gas/surface partitioning behaviour and some multiphase reaction systems involving THS, the possibility of time-dependent changes in chemical composition due to chemical reactivity that is endogenous to the deposited film has yet to be investigated. In this study, sidestream cigarette smoke was allowed to deposit on glass surfaces that were either clean or pre-coated with chemicals that may be oxidized by reactive oxygen species found in the smoke. Surface films included a low volatility antioxidant, tris(2-carboxyethyl)phosphine (TCEP), and two compounds relevant to surface films found within buildings, oleic acid (OA) and squalene (SQ). Upon deposition, oxidation products of nicotine, TCEP, OA, and SQ were formed over time periods of hours to weeks. The inherent oxidative potential of cigarette smoke deposited as a THS film can therefore initiate and sustain oxidation chemistry, transforming the chemical composition of surface films over long periods of time after initial smoke deposition. An interpretation of the THS oxidation results is provided in the context of other types of deposited particulate air pollutants with known oxidative potential that may be introduced to indoor environments. Continued study of THS and deposited surface films found indoors should consider the concept that chemical reservoirs found on surfaces may be reactive, that the chemical composition of indoor surface films may be time-dependent, and that the deposition of aerosol particles can act as a mechanism to initiate oxidation in surface films. 

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3. First-principles surface energies for monoclinic Ga2O3 and Al2O3 and consequences for cracking of (Al x Ga1− x )2O3

   https://doi.org/10.1063/5.0019915  

   Mu, Sai; Wang, Mengen; Peelaers, Hartwin; Van_de_Walle, Chris_G (September 2020, APL Materials)

   Crack formation limits the growth of (AlxGa1−x)2O3 epitaxial films on Ga2O3 substrates. We employ first-principles calculations to determine the brittle fracture toughness of such films for three growth orientations of the monoclinic structure: [100], [010], and [001]. Surface energies and elastic constants are computed for the end compounds—monoclinic Ga2O3 and Al2O3—and used to interpolate to (AlxGa1−x)2O3 alloys. The appropriate crack plane for each orientation is determined, and the corresponding critical thicknesses are calculated based on Griffith’s theory, which relies on the balance between elastic energy and surface energy. We obtain lower bounds for the critical thickness, which compare well with available experiments. We also perform an in-depth analysis of surface energies for both relaxed and unrelaxed surfaces, providing important insights into the factors that determine the relative stability of different surfaces. Our study provides physical insights into surface stability, crack planes, and the different degrees of crack formation in (AlxGa1−x)2O3 films for different growth orientations. 

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4. Polar in-plane surface orientation of a ferroelectric nematic liquid crystal: Polar monodomains and twisted state electro-optics

   https://doi.org/10.1073/pnas.2104092118  

   Chen, Xi; Korblova, Eva; Glaser, Matthew A.; Maclennan, Joseph E.; Walba, David M.; Clark, Noel A. (May 2021, Proceedings of the National Academy of Sciences)

   We show that surface interactions can vectorially structure the three-dimensional polarization field of a ferroelectric fluid. The contact between a ferroelectric nematic liquid crystal and a surface with in-plane polarity generates a preferred in-plane orientation of the polarization field at that interface. This is a route to the formation of fluid or glassy monodomains of high polarization without the need for electric field poling. For example, unidirectional buffing of polyimide films on planar surfaces to give quadrupolar in-plane anisotropy also induces macroscopic in-plane polar order at the surfaces, enabling the formation of a variety of azimuthal polar director structures in the cell interior, including uniform and twisted states. In a π-twist cell, obtained with antiparallel, unidirectional buffing on opposing surfaces, we demonstrate three distinct modes of ferroelectric nematic electro-optic response: intrinsic, viscosity-limited, field-induced molecular reorientation; field-induced motion of domain walls separating twisted states of opposite chirality; and propagation of polarization reorientation solitons from the cell plates to the cell center upon field reversal. Chirally doped ferroelectric nematics in antiparallel-rubbed cells produce Grandjean textures of helical twist that can be unwound via field-induced polar surface reorientation transitions. Fields required are in the 3-V/mm range, indicating an in-plane polar anchoring energy of w P ∼3 × 10 −3 J/m 2 . 

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5. All-graphene-based open fluidics for pumpless, small-scale fluid transport via laser-controlled wettability patterning

   https://doi.org/10.1039/D0NH00376J  

   Hall, Lucas S.; Hwang, Dohgyu; Chen, Bolin; Van Belle, Bryan; Johnson, Zachary T.; Hondred, John A.; Gomes, Carmen L.; Bartlett, Michael D.; Claussen, Jonathan C. (January 2021, Nanoscale Horizons)

   null (Ed.)

   Open microfluidics have emerged as a low-cost, pumpless alternative strategy to conventional microfluidics for delivery of fluid for a wide variety of applications including rapid biochemical analysis and medical diagnosis. However, creating open microfluidics by tuning the wettability of surfaces typically requires sophisticated cleanroom processes that are unamenable to scalable manufacturing. Herein, we present a simple approach to develop open microfluidic platforms by manipulating the surface wettability of spin-coated graphene ink films on flexible polyethylene terephthalate via laser-controlled patterning. Wedge-shaped hydrophilic tracks surrounded by superhydrophobic walls are created within the graphene films by scribing micron-sized grooves into the graphene with a CO 2 laser. This scribing process is used to make superhydrophobic walls (water contact angle ∼160°) that delineate hydrophilic tracks (created through an oxygen plasma pretreatment) on the graphene for fluid transport. These all-graphene open microfluidic tracks are capable of transporting liquid droplets with a velocity of 20 mm s −1 on a level surface and uphill at elevation angles of 7° as well as transporting fluid in bifurcating cross and tree branches. The all-graphene open microfluidic manufacturing technique is rapid and amenable to scalable manufacturing, and consequently offers an alternative pumpless strategy to conventional microfluidics and creates possibilities for diverse applications in fluid transport. 

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