Hierarchically patterned polyurethane microgrooves featuring nanopillars or nanoholes for neurite elongation and alignment

• Lester Uy Vinzons,
• Guo-Chung Dong and
• Shu-Ping Lin

Beilstein J. Nanotechnol. 2023, 14, 1157–1168, doi:10.3762/bjnano.14.96

• increase in CA on the nanopillar and nanohole substrates may be due to either a Wenzel- or a Cassie-type of wetting [22]. To improve wetting on the substrates, we treated our samples with mild O2 plasma before laminin incubation. After plasma treatment, all samples became hydrophilic (CA < 80°), with the

Roll-to-roll fabrication of superhydrophobic pads covered with nanofur for the efficient clean-up of oil spills

• Patrick Weiser,
• Robin Kietz,
• Marc Schneider,
• Matthias Worgull and
• Hendrik Hölscher

Beilstein J. Nanotechnol. 2022, 13, 1228–1239, doi:10.3762/bjnano.13.102

• might slow the speed at which water droplets roll off even if the surface is still superhydrophobic. If the conveying speed is set too high, the hairs are too short and water droplets might touch the surface between the hairs. In this so-called Wenzel state, the droplets are pinned [16]. The video in

Design of a biomimetic, small-scale artificial leaf surface for the study of environmental interactions

• Miriam Anna Huth,
• Axel Huth,
• Lukas Schreiber and
• Kerstin Koch

Beilstein J. Nanotechnol. 2022, 13, 944–957, doi:10.3762/bjnano.13.83

• homogeneous, smooth, non-deformable, and inert surface. Natural and technical surfaces hardly correspond to these ideal conditions. Wenzel [33] and Cassie and Baxter [34] studied CAs on rough surfaces, assuming that the liquid penetrates perfectly into the depressions of the surface (homogeneous wetting

• ). Cassie and Baxter [34] describe heterogeneous wetting in which the liquid does not penetrate the depressions of the surface. Air pockets form under the liquid, which reduce the contact between the solid surface and the liquid. In nature, ideal Wenzel or Cassie–Baxter wetting stages rarely occur. However

• cultures, however, showed clear damage in the wax layer (removed and flattened crystals) on the leaf surfaces in some cases (Supporting Information File 1, Figure S3). Presumably, a transition to Wenzel wetting takes place at damaged or dirty areas, so that the droplets no longer roll off. In the case of a

A 3D-polyphenylalanine network inside porous alumina: Synthesis and characterization of an inorganic–organic composite membrane

• Jonathan Stott and
• Jörg J. Schneider

Beilstein J. Nanotechnol. 2020, 11, 938–951, doi:10.3762/bjnano.11.78

• ), the model of Wenzel can be applied [55][56][57]. Here we assume a relatively high fraction, f, because no roll off angles or high adhesion properties of the water droplets are observed (see Supporting Information File 1, Figure S5). The morphology of the polymer structure within the pore volume is

Synthesis of highly active ETS-10-based titanosilicate for heterogeneously catalyzed transesterification of triglycerides

• Muhammad A. Zaheer,
• David Poppitz,
• Khavar Feyzullayeva,
• Marianne Wenzel,
• Jörg Matysik,
• Radomir Ljupkovic,
• Aleksandra Zarubica,
• Alexander A. Karavaev,
• Andreas Pöppl,
• Roger Gläser and
• Muslim Dvoyashkin

Beilstein J. Nanotechnol. 2019, 10, 2039–2061, doi:10.3762/bjnano.10.200

• Muhammad A. Zaheer David Poppitz Khavar Feyzullayeva Marianne Wenzel Jorg Matysik Radomir Ljupkovic Aleksandra Zarubica Alexander A. Karavaev Andreas Poppl Roger Glaser Muslim Dvoyashkin Institute of Chemical Technology, Universität Leipzig, Linnéstraße 3, 04103 Leipzig, Germany Institute of

Biomimetic surface structures in steel fabricated with femtosecond laser pulses: influence of laser rescanning on morphology and wettability

• Camilo Florian Baron,
• Alexandros Mimidis,
• Daniel Puerto,
• Evangelos Skoulas,
• Emmanuel Stratakis,
• Javier Solis and
• Jan Siegel

Beilstein J. Nanotechnol. 2018, 9, 2802–2812, doi:10.3762/bjnano.9.262

• , also termed Wenzel and Cassie-Baxter regimes, respectively, wetting can in principle be described by taking into account the interfacial tension between substrate, liquid, and vapor and the surface geometry. Yet, the sole presence of one or another regime is a matter of debate [45]. While this

Preparation and morphology-dependent wettability of porous alumina membranes

• Dmitry L. Shimanovich,
• Alla I. Vorobjova,
• Daria I. Tishkevich,
• Alex V. Trukhanov,
• Maxim V. Zdorovets and
• Artem L. Kozlovskiy

Beilstein J. Nanotechnol. 2018, 9, 1423–1436, doi:10.3762/bjnano.9.135

• altered from the Wenzel to the Cassie state. The main aim of this study is preparation and investigation of the wetting properties of porous membranes with an ordered structure based on anodic alumina (PAMs) with different pore lengths and diameters. For this purpose we carry out a comparative analysis of

• –Baxter model is more suitable for the description of large thickness oxides with small pores (received, for example, in sulfuric electrolyte). The Wenzel model was found to be more suitable for the description of small thickness oxides (less than 30 µm) with larger diameter pores (received, for example

• ) after etching of the barrier layer. Schematic representation of the different models for pore wetting: A – Cassie–Baxter model [38], B – Wenzel model [38], C, D – schemes to explain wetting in our study. Contact angle as a function of surface topology (middle column images (B, E, H) are outer surfaces

Interface conditions of roughness-induced superoleophilic and superoleophobic surfaces immersed in hexadecane and ethylene glycol

• Yifan Li,
• Yunlu Pan and
• Xuezeng Zhao

Beilstein J. Nanotechnol. 2017, 8, 2504–2514, doi:10.3762/bjnano.8.250

• significantly inhibit the degree of boundary slip on both superoleophilic surfaces in Wenzel state and superoleophobic surfaces in Cassie state immersed in oil. The oleic systems were likely to enhance boundary slip and resulted in a corresponding reduction in drag with decreasing roughness on the solid–oil

• using an AFM with a colloidal probe in contact mode. Reference surface of superoleophilic and superoleophobic samples were defined and the effective slip lengths were obtained. The situation of superoleophilic surfaces in Wenzel state and superoleophobic surfaces in Cassie state were discussed in this

Surfactant-induced enhancement of droplet adhesion in superhydrophobic soybean (Glycine max L.) leaves

• Oliver Hagedorn,
• Ingo Fleute-Schlachter,
• Hans Georg Mainx,
• Viktoria Zeisler-Diehl and
• Kerstin Koch

Beilstein J. Nanotechnol. 2017, 8, 2345–2356, doi:10.3762/bjnano.8.234

• applied liquid also depends on the wetting mode. In the Wenzel mode [26] an applied water droplet penetrates into cavities formed by the surface structures, increasing the contact area, and resulting in high hysteresis of the applied liquid. In Cassie–Baxter mode [27] air remains in the surface cavities

• wetting regime from Cassie–Baxter mode to an intermediate wetting state or complete Wenzel wetting state, characterized by a high CA and a high TA. Differences in the solubility of wax types with different chemical composition have been described for organic solvents. Thus, plant species with different

Air–water interface of submerged superhydrophobic surfaces imaged by atomic force microscopy

• Markus Moosmann,
• Thomas Schimmel,
• Wilhelm Barthlott and
• Matthias Mail

Beilstein J. Nanotechnol. 2017, 8, 1671–1679, doi:10.3762/bjnano.8.167

• cantilevers on the right-hand side marked in grey. Below the lower cantilever the sample is already wetted (Wenzel state), as marked with white crosses. The rest of the sample shows air retention (Cassie–Baxter state). Figure 4b was taken after three minutes. In the upper left area, the air layer has

Three-gradient regular solution model for simple liquids wetting complex surface topologies

• Sabine Akerboom,
• Marleen Kamperman and
• Frans A. M. Leermakers

Beilstein J. Nanotechnol. 2016, 7, 1377–1396, doi:10.3762/bjnano.7.129

• (contact angle on a smooth surface θY < 90°) to hydrophobic (effective advancing contact angle θ > 90°). Both the Wenzel wetting state, that is cavities under the liquid are filled, as well as the Cassie–Baxter wetting state, that is air entrapment in the cavities under the liquid, were observed using our

• ] with r the roughness of the surface (true contact area/projected area). This is called the Wenzel state, and it always magnifies the underlying wetting properties: θ decreases for hydrophilic materials and increases for hydrophobic materials. As the structured surfaces of interest, which are composed

• of a hydrophilic material, show an increase in θ, this implies that the droplet in these systems cannot be in the Wenzel state, or that the assumption of this model, namely that the parameter r captures all features of a surface topography relevant for the final droplet shape, is too simplistic. A

Nanostructured superhydrophobic films synthesized by electrodeposition of fluorinated polyindoles

• Gabriela Ramos Chagas,
• Thierry Darmanin and
• Frédéric Guittard

Beilstein J. Nanotechnol. 2015, 6, 2078–2087, doi:10.3762/bjnano.6.212

• C6F13 fluorinated chains have also the highest oleophobicity even if the oil contact angles are relatively low. Indeed, two equations (the Wenzel and the Cassie–Baxter equation) [36][37] depending on θY are very often used to explain the effect of the surface roughness on the wetting properties. In the

• Wenzel equation [36] (cos θ = r·cos θY, where r is a roughness parameter), the surface roughness can increase θ, but only if θY > 90°. Hence, it is possible to have an extremely high θwater, but the contact angle hysteresis (H) is usually high because the surface roughness increases also the solid–liquid

Charge carrier mobility and electronic properties of Al(Op)₃: impact of excimer formation

• Andrea Magri,
• Pascal Friederich,
• Bernhard Schäfer,
• Valeria Fattori,
• Xiangnan Sun,
• Timo Strunk,
• Velimir Meded,
• Luis E. Hueso,
• Wolfgang Wenzel and
• Mario Ruben

Beilstein J. Nanotechnol. 2015, 6, 1107–1115, doi:10.3762/bjnano.6.112

• Andrea Magri Pascal Friederich Bernhard Schafer Valeria Fattori Xiangnan Sun Timo Strunk Velimir Meded Luis E. Hueso Wolfgang Wenzel Mario Ruben Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76344 Eggenstein-Leopoldshafen, Germany Istituto per la Sintesi Organica e

From lithium to sodium: cell chemistry of room temperature sodium–air and sodium–sulfur batteries

• Philipp Adelhelm,
• Pascal Hartmann,
• Conrad L. Bender,
• Martin Busche,
• Christine Eufinger and
• Juergen Janek

Beilstein J. Nanotechnol. 2015, 6, 1016–1055, doi:10.3762/bjnano.6.105

Exploiting the hierarchical morphology of single-walled and multi-walled carbon nanotube films for highly hydrophobic coatings

• Francesco De Nicola,
• Paola Castrucci,
• Manuela Scarselli,
• Francesca Nanni,
• Ilaria Cacciotti and
• Maurizio De Crescenzi

Beilstein J. Nanotechnol. 2015, 6, 353–360, doi:10.3762/bjnano.6.34

• wettability. It is indeed well-established [12][13] that on composite rough surfaces a hierarchical morphology may induce a wetting transition from Wenzel [1] to Cassie–Baxter [9] state owing to air trapping. Moreover, this transition may occur by passing through thermodynamically metastable states [13][14

• range of stability of the Cassie–Baxter state [14][17]. Conversely, a negative consequence of metastability is that it might prevent or slow down the transition between Wenzel and Cassie–Baxter states [14][17]. Moreover, biomimetics [18][19] may be exploited in order to realize cutting edge artificial

• petals [2] in which micropapillae are made of nanopapillae, improves the hydrophobic behavior of carbon nanotube coatings compared to bare SWCNT and MWCNT films. Moreover, we report for the first time the experimental Wenzel/Cassie–Baxter phase diagram [8][12][17] for a carbon nanotube surface, showing

Measuring air layer volumes retained by submerged floating-ferns Salvinia and biomimetic superhydrophobic surfaces

• Matthias J. Mayser,
• Holger F. Bohn,
• Meike Reker and
• Wilhelm Barthlott

Beilstein J. Nanotechnol. 2014, 5, 812–821, doi:10.3762/bjnano.5.93

• superhydrophobicity can only be achieved by a combination of a hydrophobic surface chemistry and surface structures on the micro and nano scale [11]. On these structured surfaces superhydrophobicity can occur either in the fully wetted state as described by Wenzel [12] or in the form of water sitting only on the tips

• of the surface structures (Cassie–Baxter wetting state) [13]. The contact angle of water droplets can be equally high in both wetting states [14][15]. However, in the Wenzel wetting state the water is in full contact with the surface and individual droplets adhere firmly [16]. In contrast to this in

• water interface, which is not smooth but sagging in between the pillars, so that the real air volume should be slightly smaller than the theoretical value [37]. Another reason could be defects in the hydrophobic coating, leading to small areas, where there might have happened a transition to the Wenzel

Magnetic anisotropy of graphene quantum dots decorated with a ruthenium adatom

• Igor Beljakov,
• Velimir Meded,
• Franz Symalla,
• Karin Fink,
• Sam Shallcross and
• Wolfgang Wenzel

Beilstein J. Nanotechnol. 2013, 4, 441–445, doi:10.3762/bjnano.4.51

• Igor Beljakov Velimir Meded Franz Symalla Karin Fink Sam Shallcross Wolfgang Wenzel Institute of Nanotechnology (INT), KIT, Karlsruhe, Germany Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany 10.3762/bjnano.4.51 Abstract The creation of magnetic storage devices by

Hierarchically structured superhydrophobic flowers with low hysteresis of the wild pansy (Viola tricolor) – new design principles for biomimetic materials

• Anna J. Schulte,
• Damian M. Droste,
• Kerstin Koch and
• Wilhelm Barthlott

Beilstein J. Nanotechnol. 2011, 2, 228–236, doi:10.3762/bjnano.2.27

• by dust, pollen or even hydrophilic particles such as grime are carried away by water droplets which results in a clean surface [4]. Two distinct models are proposed to explain the wetting behavior of rough surfaces. In the Wenzel model [11] roughness increases a solid surface area; this

• geometrically enhances its hydrophobicity. In the Cassie–Baxter model [12] air remains trapped below the droplet in the surface cavities, which also leads to a superhydrophobic behavior, because the droplet sits partially on air [13]. The Wenzel model describes homogeneous wetting by the following equation

• volume. The CAH occurs due to surface roughness and heterogeneity [14][15]. Low CAH results in a low TA, which describes the TA of a surface at which an applied water droplet starts to move [15]. Nowadays, transitional states between the Wenzel and Cassie–Baxter states have been discovered. Wang and

Moisture harvesting and water transport through specialized micro-structures on the integument of lizards

• Philipp Comanns,
• Christian Effertz,
• Florian Hischen,
• Konrad Staudt,
• Wolfgang Böhme and
• Werner Baumgartner

Beilstein J. Nanotechnol. 2011, 2, 204–214, doi:10.3762/bjnano.2.24

• unstructured resin as exemplified in the supplementary videos (Supporting Information Files 5–6). It is generally known that structuring, i.e., increased roughness of a hydrophilic material results in a decreased contact angle [16]. Assuming a Wenzel-model [16][17] for the wetting of the lizard scales however

Superhydrophobicity in perfection: the outstanding properties of the lotus leaf

• Hans J. Ensikat,
• Petra Ditsche-Kuru,
• Christoph Neinhuis and
• Wilhelm Barthlott

Beilstein J. Nanotechnol. 2011, 2, 152–161, doi:10.3762/bjnano.2.19

• contact with water [20] and to prove the theories such as those of Wenzel or Cassie and Baxter. For precise modelling of the behaviour of natural water repellent surfaces, an exact knowledge of the chemical composition and molecular structure are essential. Resistance against environmental stress The

• retention of the Cassie state with only partial contact between surface and water – an intrusion of water between the surface structures must be avoided. When the air layer is displaced by water, the water repellency is lost and the surface becomes wet (Wenzel state). The pressure which is necessary to

Capillary origami: superhydrophobic ribbon surfaces and liquid marbles

• Glen McHale,
• Michael I. Newton,
• Neil J. Shirtcliffe and
• Nicasio R. Geraldi

Beilstein J. Nanotechnol. 2011, 2, 145–151, doi:10.3762/bjnano.2.18

• origami or droplet wrapping. In this work, we consider how the conditions for the spontaneous, capillary induced, folding of a thin ribbon substrate might be altered by a rigid surface structure that, for a rigid substrate, would be expected to create Cassie–Baxter and Wenzel effects. For smooth thin

• interfacial energies suggests that the tendency for droplet wrapping can be suppressed for some liquids by providing the flexible solid surface with a rigid topographic structure. In general, it is known that when a liquid interacts with such a structure it can either fully penetrate the structure (the Wenzel

• case) or it can bridge between the asperities of the structure (the Cassie–Baxter case). In this report, we show theoretically that droplet wrapping should occur with both types of solid–liquid contact. We also derive a condition for the transition between the Cassie–Baxter and Wenzel type droplet

Biomimetics inspired surfaces for drag reduction and oleophobicity/philicity

• Bharat Bhushan

Beilstein J. Nanotechnol. 2011, 2, 66–84, doi:10.3762/bjnano.2.9

• ) shows the measured static contact angle as a function of pitch between the pillars for a water droplet (circle) and an oil droplet (cross) in air. The data are compared with predicted static contact angle values obtained using Wenzel and Cassie–Baxter equations [20] (solid lines) with a measured value

• responsible for the propensity of air pocket formation. The sudden drop at a pitch value of about 30 μm corresponds to the transition from the Cassie–Baxter to the Wenzel regime. The experimental observations for the transition are comparable to the value predicted from Wenzel and Cassie–Baxter equations. At

• pitch values as predicted from Wenzel equation. As mentioned earlier, the surface tension of the oil–air interface is very low for hexadecane. Therefore, it is observed that from Equation 11 the surface tension of solid–oil interface (γSO) is lower than that of solid–water interface (γSW), resulting in