Ice adhesion of PDMS surfaces with balanced elastic and water-repellent properties

This research was supported by the project MAT2017-82182-R funded by the State Research Agency (SRA) of Spain and European Regional Development Fund (ERDF). Funding for open access charge: Universidad de Granada / CBUAHypothesis: Ice adhesion to rigid materials is reduced with low energy surfaces of high receding contact angles. However, their adhesion strength values are above the threshold value to be considered as icephobic materials. Surface deformability is a promising route to further reduce ice adhesion. Experiments: In this work, we prepared elastomer surfaces with a wide range of elastic moduli and hydrophobicity degree and we measured their ice adhesion strength. Moreover, we also explored the deicing performance of oil-infused elastomeric surfaces. The ice adhesion was characterized by two detachment modes: tensile and shear. Findings: The variety of elastomeric surfaces allowed us to simultaneously analyze the ice adhesion dependence with deformability and contact angle hysteresis. We found that the impact of these properties depends on the detachment mode, being deformability more important in shear mode and hydrophobicity more relevant in tensile mode. In addition, oil infusion further reduces ice adhesion due to the interfacial slippage. From an optimal balance between deformability and hydrophobicity, we were able to identify surfaces with super-low ice adhesion.MAT2017-82182-R State Research Agency (SRA)European Regional Development Fund (ERDF)Universidad de Granada / CBU

Oscillating Magnetic Drop: How to Grade Water-Repellent Surfaces

Evaluation of superhydrophobic (SH) surfaces based on contact angle measurements is challenging due to the high mobility of drops and the resolution limits of optical goniometry. For this reason, some alternatives to drop-shape methods have been proposed such as the damped-oscillatory motion of ferrofluid sessile drops produced by an external magnetic field. This approach provides information on surface friction (lateral/shear adhesion) from the kinetic energy dissipation of the drop. In this work, we used this method to compare the low adhesion of four commercial SH coatings (Neverwet, WX2100, Ultraever dry, Hydrobead) formed on glass substrates. As ferrofluid, we used a maghemite aqueous suspension (2% v/v) synthesized ad hoc. The rolling magnetic drop is used as a probe to explore shear solid–liquid adhesion. Additionally, drop energy dissipates due to velocity-dependent viscous stresses developed close to the solid–liquid interface. By fitting the damped harmonic oscillations, we estimated the decay time on each coating. The SH coatings were statistically different by using the mean damping time. The differences found between SH coatings could be ascribed to surface–drop adhesion (contact angle hysteresis and apparent contact area). By using this methodology, we were able to grade meaningfully the liquid-repelling properties of superhydrophobic surfaces.This research was financed by the State Research Agency (SRA) and European Regional Development Fund (ERDF) through the project MAT2017-82182-R. Fernando Vereda acknowledges financial support from MAT 2016-78778-R and PCIN-2015-051 projects (Spain)

Water-Repellent Galvanized Steel Surfaces Obtained by Sintering of Zinc Nanopowder

Galvanized steel surfaces are widely used in industry as a solution to prevent corrosion of steel tools that operate in outdoor or corrosive and oxidative environments. These objects are coated with a zinc protective layer deposited by hot dip galvanization. Turning the surface of galvanized steel tools into superhydrophobic may lead to very useful functionalities, although it may be a difficult task, because the preservation of the thin zinc layer is a claim. We propose herein the use of a bottom-up approach based on sandblasting, followed by sintering of zinc nanoparticles on the galvanized steel substrate, which allowed us to produce a zinc-made hierarchical structure required for superhydrophobicity. These samples acquired a double-scale structure that led to superhydrophobicity when they were later hydrophobized with a thin fluoropolymer layer. We found that sandblasting might be useful but not mandatory, unlike the sintering process, which was essential to reach superhydrophobicity. We found that, under certain experimental conditions, the surfaces showed outstanding water-repellent properties. We observed that the sandblasting on galvanized steel caused more damage than the sintering process. Sintering of low-melting-point metal nanoparticles was revealed as a promising strategy to fabricate functional metallic surfaces.Ministerio de Ciencia e Innovación: PID2020-116082GB-I00.Program FEDER- Junta de Andaluciá : B-FQM-670-UGR20.European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 955612 (NanoPaInt

Non-Stick Coatings in Aluminium Molds for the Production of Polyurethane Foam

The manufacturing of polyurethane foam is a process of great industrial importance in the automotive and furniture sector. The operation of demolding is the most delicate, since the foam sticks firmly to the walls of the mold onto which it has spread. In order to avoid the use of demolding agents, the proposal is to coat the inside of the molds with non-stick coatings. In this work, three types of different coatings were studied: fluoropolymers, ceramics, and elastomers. After carrying out different tests in the laboratory, two fluoropolymer coatings (PFA (perfluoroalkoxy) and PTFE (polytetrafluoroethylene)) were selected for a test at the industrial level and, after 1500 cycles of demolding, it was experimentally proven that the PFA coating is the most adequate for the use studied.This study was funded by the European Fund for Regional Development, the Ministry of Economy and Competitiveness of the Government of Spain and the Centre for Industrial Technological Development (CDTI) (nº ITC-2015237), as well as by Project for Excellence Andalusian Research Plan (P12-FQM-1443)

Non-Stick Coatings in Aluminium Molds for the Production of Polyurethane Foam

The manufacturing of polyurethane foam is a process of great industrial importance in the automotive and furniture sector. The operation of demolding is the most delicate, since the foam sticks firmly to the walls of the mold onto which it has spread. In order to avoid the use of demolding agents, the proposal is to coat the inside of the molds with non-stick coatings. In this work, three types of different coatings were studied: fluoropolymers, ceramics, and elastomers. After carrying out different tests in the laboratory, two fluoropolymer coatings (PFA (perfluoroalkoxy) and PTFE (polytetrafluoroethylene)) were selected for a test at the industrial level and, after 1500 cycles of demolding, it was experimentally proven that the PFA coating is the most adequate for the use studie

Water-Repellent Fluoropolymer-Based Coatings

We would like to thank to the company TECNIMACOR S.L. (Córdoba, Spain) for the preparation of the coatings studied in this work.Fluoropolymer-based coatings are widely used for release applications. However, these hydrophobic surfaces do not reveal a significantly low adhesion. Water repellency incorporated to fluoropolymer coatings might enhance their release performance. In this work, we focused on the surface texturing of a well-known polytetrafluoroethylene (PTFE)-based coating. We explored as texturing routes: sanding, sandblasting and laser ablation. We examined the surface roughness with white light confocal microscopy and the surface morphology with environmental scanning electron microscopy (ESEM). Water-repellent fluoropolymer coatings were reproduced in all cases, although with different degree, parametrized with bounces of water drops (4–5 μL). Laser ablation enabled the lowest adhesion of coatings with 24 ± 2 bounces. This result and the current development of laser patterning for industry assure the incipient use of laser ablation for release coatings.The research was funded by the projects MAT2014-60615-R and MAT2017-82182-R, funded by the Spanish Ministry of Economy and Competitiveness (MINECO-FEDER)

Effect of Hyaluronic Acid and Pluronic-F68 on the Surface Properties of Foam as a Delivery System for Polidocanol in Sclerotherapy

The use of foams to deliver bioactive agents and drugs is increasing in pharmaceutics. One example is the use of foam as a delivery system for polidocanol (POL) in sclerotherapy, with the addition of bioactive compounds to improve the delivery system being a current subject of study. This work shows the influence of two bioactive additives on the structure and stability of POL foam: hyaluronic acid (HA) and Pluronic-F68 (F68). HA is a natural non-surface-active biopolymer present in the extracellular matrix while F68 is a surface-active poloxamer that is biocompatible with plasma-derived fluids. Both additives increase the bulk viscosity of the sample, improving foam stability. However, HA doubled and F68 quadruplicated the foam half lifetime of POL. HA reduced the size and polydispersity of the bubble size distribution and increased the surface elasticity with respect to POL. Both facts have a positive impact in terms of foam stability. F68 also altered bubble structure and increased surface elasticity, again contributing to the enhancement of foam stability. The surface characterization of these systems is important, as in foam sclerotherapy it is crucial to assure the presence of POL at the surface of the bubbles in order to deliver the sclerosant agent in the target vein.Junta de Andalucia NANOFOAM-PI12.2956Instituto de Salud Carlos III Spanish Government MAT2017-82182-R RTI2018-101309-B-C21Consejeria de Economia, Conocimiento, Empresas y UniversidadEuropean Union (EU) SOMM17/6109/UG

Applications of serum albumins in delivery systems: Differences in interfacial behaviour and interacting abilities with polysaccharides

One of the major applications of SerumAlbumins is their use as delivery systems for lipophilic compounds in biomedicine. Their biomedical application is based on the similarity with Human Serum Albumin (HSA), as a fully biocompatible protein. In general, Bovine Serum Albumin (BSA) is treated as comparable to its human homologue and used as a model protein for fundamental studies since it is available in high amounts and well understood. This protein can act as a carrier for lipophilic compounds or as protective shell in an emulsion-based vehicle. Polysaccharides are generally included in these formulations in order to increase the stability and/or applicability of the carrier. In this review, themain biomedical applications of Albumins as drug delivery systems are first presented. Secondly, the differences between BSA andHSA are highlighted, exploring the similarities and differences between these proteins and their interaction with polysaccharides, both in solution and adsorbed at interfaces. Finally, the use of Albumins as emulsifiers for emulsion-based delivery systems, concretely as Liquid Lipid Nanocapsules (LLNs), is revised and discussed in terms of the differences encountered in the molecular structure and in the interfacial properties. The specific case of Hyaluronic Acid is considered as a promising additivewith important applications in biomedicine. The literatureworks are thoroughly discussed highlighting similarities and differences between BSA and HSA and their interaction with polysaccharides encountered at different structural levels, hence providing routes to control the optimal design of delivery systems.This work has been funded by the following projects, which are gratefully acknowledged: MAT2017-82182-R and RTI2018-101309-BC21 (Ministerio de Ciencia e Innovación). The authors also acknowledge “Mancomunidad de los Pueblos de la Alpujarra Granadina” for the funds raised and supplied for this research

Capilares coaxiales y procedimiento de intercambio para balanza de superficies de penetración

Número de solicitud: 009801626La presente invención se refiere a un conjunto de capilares montados de forma concéntrica conectados a un microinyector y un procedimiento para el intercambio del contenido de la gota para la construcción de una balanza de superficies de penetración por aplicación del procedimiento de medida de la tensión interfacial de la gota pendiente

Propiedades electrocinéticas y de adsorción de tensioactivos iónicos sobre celestina (So4Sr) y su aplicación a la flotación

Se hace un estudio de las propiedades electrocinéticas de la celestina en disoluciones de diferentes electrolitos inorgánicos asi como de colectores (tensioactivo) aniónicos y catiónicos. Se estudian asimismo las propiedades de absorción de tales tensioactivos proponiendose finalmente mecanismos de tales procesos. Se buscan correlaciones entre todas estas propiedades y la flotación del mineralUniversidad de Granada, Departamento de Fisica Aplicada. Leída el 18-08-198