Abstract With an increased need to solve fresh water scarcity for humanity in many places around the world, dew water harvesting is one promising approach to improve the situation. While condensation from humid air has been a research topic for many years, it is still unclear how surface wettability influences the condensation efficiency and the fresh water harvest. In this work, we contribute to bridging this knowledge gap by comparing the condensation efficiency of PDMS-coated hydrophobic and uncoated hydrophilic surfaces. We characterize the humid air velocity field to enable comparability of the present results on condensation efficiency with the results gained at other conditions. In addition, the surface wetting behavior prior to and after the condensation experiment is investigated to analyze the PDMS-coating longevity and allow to draw conclusions on their suitability for long term use in condensation applications.

Sintering granular materials involves the application of pressure and temperature to make the particulate material a permanent solid. In order to better understand this complex process, the pressure-, temperature-, and time-dependent contact behaviour of micron-sized particles has been studied in close collaboration by the groups of Luding, Staedler and Kappl within the DFG SPP PiKo. This chapter summarises the modelling advances made during the project, with direct links given to the experimental results. Two aspects have been studied: (a) the dependence of the elastic as well as frictional contact forces and torques on an applied normal pressure; and (b) the formation and evolution of adhesive bonds between particles during heat-sintering. Both contact models have been experimentally calibrated and validated, using advanced techniques such as nanoindentation and AFM. As materials, borosilicate particles were used to study the pressure-dependency, while polystyrene particles were chosen due to their low glass transition temperature to study the temperature-dependency near the transition. Combining both aspects provides a multi-purpose contact model that allows the simulations of a wide range of sinter and agglomeration processes for a variety of practically relevant materials.

We image the bending of soft micropillars as liquid drops move on them and calculate the forces hindering drop motion.

Micrometer-sized monodisperse polystyrene (PS) particles carrying a pH-responsive poly[2-(diethylamino)ethyl methacrylate] (PDEA) colloidal stabilizer were synthesized via free radical dispersion polymerization. X-ray photoelectron spectroscopy and electrophoretic measurements verified that PDEA covered the PS particle surface. At pH 3.0 and 6.3, where the PDEA is protonated and cationically charged, the PDEA-PS particles were well dispersed in aqueous media thanks to the water soluble PDEA stabilizer and slowly sedimented due to gravity and enriched at the bottom of the glass vials. At pH 10.0, where the PDEA is non-protonated and neutral, the PDEA-PS particles weakly aggregated due to non-hydrated and collapsed PDEA. These PDEA-PS particles and aggregates sedimented to the bottom. The sediment height observed at pH 10.0 was higher than those observed at pH 3.0 and 6.3 in both wet and dry systems, which indicated that a larger porosity was formed at pH 10.0. Mechanical testing experiments confirmed that the fracture toughness of the dried materials decreased with an increase of pH. The fracture toughness was found to be correlated with the degree of particle ordering in the dried particulate materials: more ordered, dense packings lead to a higher fracture toughness compared to amorphous, less dense packings. Thus, we could tune fracture toughness and degree of particle ordering by controlling the pH.

We investigated rock varnishes collected from several locations and environments worldwide by a broad range of microanalytical techniques. These techniques were selected to address the challenges posed by the chemical and structural complexity within the micrometer- to nanometer-sized structures in these geological materials. Femtosecond laser ablation-inductively coupled plasma-mass spectrometry (fs LA-ICP-MS), scanning transmission X-ray microscopy-near edge X-ray adsorption fine structure spectroscopy (STXM-NEXAFS) in combination with scanning electron microscopy (SEM) of focused ion beam (FIB) ultra-thin (100–200nm) sections, conventional and polarization microscopy, as well as electron paramagnetic resonance (EPR) measurements were used to obtain information about these rock varnishes.Rock varnishes from different environments, which cannot readily be distinguished based on their macroscopic appearance, differ significantly in their constituent elemental mass fractions, e.g., of Mn, Fe, Ni, Co, Ba, and Pb, and their rare earth element (REE) patterns. Structural characteristics such as the particle sizes of embedded dust grains, internal structures such as layers of Mn-, Fe-, and Ca -rich material, and structures such as cavities varied between varnishes from different environments and regions in the world. The EPR spectra were consistent with aged biogenic Mn oxides in all samples, but showed subtle differences between samples of different origin.Our observations allow us to separate rock varnishes into different types, with differences that might be indicators of distinct geneses. Five different types of rock varnish could be distinguished, Type I–V, of which only Type I might be used as potential paleoclimate archive. Each varnish type has specific characteristics in terms of their elemental composition, element distribution, and structures. The combination of element ratios (Mn/Ba, Al/Ni, Mn/REY, Mn/Ce, Mn/Pb, LaN/YbN, and Ce/Ce*), total REE contents, and structures can be used to separate the different types of rock varnish from each other.

Pressure-sensitive adhesive (PSA) powder consisting of particles with an adhesive polymer core and a hard nanoparticle shell morphology have been synthesized based on liquid marble technology. The PSA shows no adhesion in its original form, and shows its adhesive nature only after application of shear stress.

Multilayered nanocomposites containing iron oxide nanoparticles, strongly cemented together through a dopamine modified polymer, exhibit high resistance against elastic and plastic deformation with a Young's modulus of 17 GPa and a hardness of 1.3 GPa.

A wide range of analytical techniques were used to investigate rock varnish from different locations (Negev, Israel; Knersvlakte, South Africa; Death Valley and Mojave Desert, California): a 200nm-femtosecond laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS), an electron probe microanalyzer (EPMA), focused ion beam (FIB) slicing, and scanning transmission X-ray microscopy–near edge X-ray absorption fine structure spectroscopy (STXM–NEXAFS). This combination enables comprehensive high-spatial-resolution analysis of rock varnish. Femtosecond LA-ICP-MS and EPMA were used for quantitative determination of element concentrations. In-situ measurements were conducted on thick and thin sections with a resolution of 10–40μm and 2μm, respectively. The results demonstrate that some elements, such as Mn, Co, Pb, Ni, and Cu, are highly enriched in varnish relative to the upper continental crust (up to a factor of 100). The varnish composition is not influenced by the composition of the underlying rock, which is witnessed by plots of MnO2 vs. SiO2 contents. Furthermore, the Mn-free end members fall in the range of average dust compositions.The varnishes from the various locations show distinct differences in some elemental ratios, in particular Mn/Fe (0.3–25.1), Mn/Ba (4–170), Ni/Co (0.03–1.8) and Pb/Ni (0.4–23). The rare earth element (REE) patterns vary with LaN/YbN=3.5–12 and different degrees of Ce anomalies (Ce/Ce*=1.5–5.3).To study the internal structure of the varnish, 100–200nm thick FIB slices were prepared and mappings of Fe, Mn, N, CO32−, Ca, C, and Si at the nm scale performed. Banded internal structures of Mn, Fe and organic C were observed in the Israeli and Californian samples, however, no Fe-rich layers are present in the South African rock varnish samples. Furthermore, cavities were found that are partly filled by C, Fe, and Mn rich material. Internal structures are different for varnish from different locations, which might reflect different types of genesis. The results of the combined microanalytical techniques give important detailed insights towards unraveling the genesis of rock varnish.

We have studied the effect of bio-inspired polymers and proteins like ovalbumin, lysozyme and silicatein, which are present in the first stage of egg shell formation or in the formation of siliceous spicules of sponges, on the homogeneous formation of the liquid-amorphous calcium carbonate (LACC) precursor, by a combination of complementary methods like in situ WAXS, light scattering, TEM and cryo-TEM. Lysozyme destabilizes the LACC emulsion, whereas ovalbumin extends the lifetime of the emulsified state. We demonstrate that ovalbumin acts as a stabilizer for a polymer-induced liquid precursor (PILP) process. We propose that the liquid amorphous calcium carbonate is affected by polymers by depletion stabilization and de-emulsification rather than induced by acidic proteins and polymers during a polymer-induced liquid precursor process. Thus, the original PILP coating effect appears to be a result of a de-emulsification process of a stabilized LACC phase. Silicatein-α is responsible for the biomineralization of silica in sponges guides the self-assembly of calcite "spicules" similar to the spicules of the calcareous sponge Sycon. The self-assembled spicules, 10-300 µm in length and 5-10 µm in diameter, are composed of aligned calcite nanocrystals. The spicules are initially amorphous but transform into calcite within months, exhibiting unusual growth along [100]. While natural spicules evidence brittle failure, the synthetic spicules show an elastic response which greatly enhances bending strength. Later stages of nucleation have been studied by "trapping" nuclei from solution by shock-freezing of droplets in liquid ethane (cryo-TEM). This yields snapshots of the structure formation process at given point. In a first step the full determination of the structure of vaterite, one of the common CaCO3 polymorphs, was solved on nanometer-sized crystallites by electron crystallography. These results demonstrate that crystals that are too small for single-crystal X-ray diffraction and too difficult to solve by powder diffraction may nevertheless be amenable to accurate structure determination by electron crystallography.

A method for direct visualization of the position of nanoscale colloidal particles at air-water interfaces is presented. After assembling hard (polystyrene, poly(methyl methacrylate), silica) or soft core-shell gold-hydrogel composite (Au@PNiPAAm) colloids at the air-water interface, butylcyanoacrylate is introduced to the interface via the gas phase. Upon contact with water, an anionic polymerization reaction of the monomer is initiated and a film of poly(butylcyanoacrylate) (PBCA) is generated, entrapping the colloids at their equilibrium position at the interface. We apply this method to investigate the formation of complex, binary assembly structures directly at the interface, to visualize soft, nanoscale hydrogel colloids in the swollen state, and to visualize and quantify the equilibrium position of individual micro- and nanoscale colloids at the air-water interface depending of the amount of charge present on the particle surface. We find that the degree of deprotonation of the carboxyl group shifts the air-water contact angle, which is further confirmed by colloidal probe atomic force microscopy. Remarkably, the contact angles determined for individual colloidal particles feature a significant distribution that greatly exceeds errors attributable to the size distribution of the colloids. This finding underlines the importance of accessing soft matter on an individual particle level.

The adhesion force between a silicon nitride tip and a 1-dodecanethiol monolayer have been measured at different loading rates and different humidity. A way to extract the kinetic and interaction potential parameters for a single molecule interaction is demonstrated. The effect of the increase of van der Waals interaction strength per molecule with increasing humidity is explained by assuming a gradual adsorption of water into the tip surface hollows. The study should help in better understanding of the humidity effect on molecular level and in avoiding the underestimation of adhesion forces in micro- and nano-engineering in ambient conditions.

Tienda online donde Comprar Surface and Interfacial Forces al precio 54,00 € de Tony Burns | Stephen Breathnach | Neil Cox | Christopher Griffiths | Hans-Jurgen Butt | Michael Kappl, tienda de Libros de Medicina, Libros de Biologia - Biologia general

Forces between solid surfaces across polymer melts are poorly understood despite their importance for adhesion and composite materials. Using an atomic force microscope (AFM) this force was measured for poly(dimethyl siloxane) (PDMS) on silicon oxide. The influence of molecular weight (4.0-40 kDa) was studied. Forces are attractive for low and repulsive for high molecular weight. In addition, changing the terminal methyl group for a hydroxyl group leads to an increased probability of bridging.

The concepts of template-induced crystallization on self-assembled monolayers (SAMs) and the use of polymer additives are combined into a new strategy, where, through the cooperative interaction of a SAM matrix involved in the nucleation process, poly(acrylic acid), a dissolved polyelectrolyte, and the dissolved ions, hierarchically ordered mineral structures are formed. The adsorption of poly(acrylic acid) to the SAM is monitored using a quartz microbalance. Transmission electron microscopy measurements on samples that are taken from polyacrylate solution in short intervals after the start of the reaction reveals that nanometer-sized particles pre-formed in solution are being attached to the polymer template. These CaCO3 nanoparticles are still amorphous 20 min after the start of the mineralization process; the transformation from the amorphous to the crystalline phase takes place within the first 60 min of the reaction. The morphologies of the crystalline products exhibit characteristic differences from those that are obtained in crystallization experiments on self-assembled monolayers without the polyelectrolyte. This model of cooperative formation of vaterite nanowires represents an alternative to current models of structure formation, where two-phase systems (e.g., microemulsions or foams) act as a structure-directing interface, or the mineralization process is caused by the diffusion of a hydrolyzable component from a non-aqueous into an aqueous phase.