Substrate-mediated effects in photothermal patterning of alkanethiol self-assembled monolayers with microfocused continuous-wave lasers

• Anja Schröter,
• Mark Kalus and
• Nils Hartmann

Beilstein J. Nanotechnol. 2012, 3, 65–74, doi:10.3762/bjnano.3.8

• only [32]. HDT coated substrates are characterized by contact-angle measurements and infrared reflection–absorption spectroscopy (IRRAS). Static water contact angles are about 109°. IR measurements show no difference for all samples considered here. A typical spectrum is shown in Figure 3, and peak

• distinct immersion times on a single sample (Figure 8). After etching, the samples were rinsed in deionized water and blown dry with argon. For the characterization of bare and HDT-coated substrates, UV–vis spectroscopy, laser reflectance and transmittance measurements, contact angle measurements and

Octadecyltrichlorosilane (OTS)-coated ionic liquid drops: Micro-reactors for homogenous catalytic reactions at designated interfaces

• Xiaoning Zhang and
• Yuguang Cai

Beilstein J. Nanotechnol. 2012, 3, 33–39, doi:10.3762/bjnano.3.4

• × 8 OTSpd disc arrays were fabricated on the OTS film. The size of the array was 50 × 50 μm2. Coating IL on OTSpd patterns [Bmim]Cl was purchased from Sigma-Aldrich. It has a melting point of 70 °C and an advancing contact angle of 88° on OTS film [22]. In a sealed vial, 10 g [Bmim]Cl powder was

Self-assembled monolayers and titanium dioxide: From surface patterning to potential applications

• Yaron Paz

Beilstein J. Nanotechnol. 2011, 2, 845–861, doi:10.3762/bjnano.2.94

• substrate effect on the onset of burning and on the temperature dependence of the process [22]. Data on contact-angle comparisons between organosilanes on silica and on titania is quite scarce. In this respect, contact-angle measurements of CVD-made tetrafunctional cyclic siloxane monolayers (1,3,5,7

• -tetramethylcyclotetrasiloxane (C4H16O4Si4)) did not reveal much of a difference between SAMs on oxidized titanium versus SAMs on oxidized aluminum [23]. In both cases, the water contact angle was found to be 103° when the CVD process took place at 80 °C, and 163° when the process took place at 180 °C. The n-hexadecane contact

• relatively weak carbamate linkage with the surface [32]. Here, water contact-angle hysteresis for the SAM-covered TiO2 surfaces were found to be larger than that observed for the SAM-covered SiO2 surface, suggesting that alkyl isocyanate SAMs on TiO2 were more disordered and/or were less densely packed

Approaches to nanostructure control and functionalizations of polymer@silica hybrid nanograss generated by biomimetic silica mineralization on a self-assembled polyamine layer

• Jian-Jun Yuan and
• Ren-Hua Jin

Beilstein J. Nanotechnol. 2011, 2, 760–773, doi:10.3762/bjnano.2.84

• ambient conditions, exhibits photoresponsive surface wettability through hydrophobic modification and light irradiation [44]. However, this surface failed to be superhydrophobic (i.e., water contact angle >150°) probably due to the relatively low surface roughness. In this work, by depositing the titania

• @titania composite nanograss surface was superhydrophilic (with θ = 0°) due to the high roughness and surface energy. After treatment with decyltrimethoxysilane (DecTMS) [46], the surface changed to become superhydrophobic with a water contact angle of about 179.8°. The water contact angles decreased to

• water contact angle could be attributed to the degradation of the low-surface-energy alkyl group due to the photocatalytic activity of anatase titania [47]. This was further confirmed by a simple control experiment. A superhydrophobic silica nanograss surface was produced by a similar DecTMS treatment

Fabrication of multi-parametric platforms based on nanocone arrays for determination of cellular response

• Lindarti Purwaningsih,
• Tobias Schoen,
• Tobias Wolfram,
• Claudia Pacholski and
• Joachim P. Spatz

Beilstein J. Nanotechnol. 2011, 2, 545–551, doi:10.3762/bjnano.2.58

• , respectively. Contact angle measurements were carried out prior to the surface functionalizations in order to determine the intrinsic hydrophobicity resulting from the nanostructure. Figure S2 (Supporting Information File 1) illustrates the contact angle measurements taken from nanocone arrays prepared from

• °). Attaching biomolecules to the surfaces lowers the contact angle to values of approximately 20° proving that the hydrophobicity/hydrophilicity of the substrates is a constant parameter in the following cell experiments. The potential of the substrates to support neural cell adhesion was tested with SHSY5Y

Micro to nano: Surface size scale and superhydrophobicity

• Christian Dorrer and
• Jürgen Rühe

Beilstein J. Nanotechnol. 2011, 2, 327–332, doi:10.3762/bjnano.2.38

• post surfaces for which all parameters except for the surface size scale were held constant. It was found that a critical transition from “sticky superhydrophobic” (composite state with large contact angle hysteresis) to “truly superhydrophobic” (composite state with low hysteresis) takes place as the

• size of the surface features reaches 1 μm. Keywords: contact angle; hysteresis; superhydrophobic; wetting; Introduction Superhydrophobic surfaces have recently been the focus of considerable scientific interest [1][2][3][4][5][6][7][8][9][10]. This is due to the fact that artificial superhydrophobic

• ). For this situation, Cassie’s original theory computes the contact angle (CA) of a drop from the CA on the smooth material, θS, and the fraction of the drop footprint in contact with the solid, the solid fraction , according to [11]: The contact line samples the different components of the composite

Dynamics of capillary infiltration of liquids into a highly aligned multi-walled carbon nanotube film

• Sławomir Boncel,
• Krzysztof Z. Walczak and
• Krzysztof K. K. Koziol

Beilstein J. Nanotechnol. 2011, 2, 311–317, doi:10.3762/bjnano.2.36

• density of nanotube packing, the thermodynamics of the infiltration process (wettability) were described by the contact angle between the nanotube wall and a liquid meniscus (θ). Once the wettability criterion (θ < 90°) was met, the HACNT film (of free volume equal to 91%) was penetrated gradually by the

• specify the Hildebrand solubility parameter (δ) as crucial towards convenient three-modal classification: dispersion, swelling or precipitation [15][16][17][18]. For evaluation of wettability of HACNT arrays, an approach based on the direct measurement of contact angle between interfaces of nanotube film

• and liquids was applied [19][20][21]. In order to verify critical parameters for wetting of HACNT films, we present here a simple and clear-cut approach. Our concept is based on a combination of thermodynamic and kinetic stipulation. The first parameter, the contact angle between HACNT film and the

Recrystallization of tubules from natural lotus (Nelumbo nucifera) wax on a Au(111) surface

• Sujit Kumar Dora and
• Klaus Wandelt

Beilstein J. Nanotechnol. 2011, 2, 261–267, doi:10.3762/bjnano.2.30

• HOPG (non-polar) to horizontally oriented tubules on polar substrates, e.g., silicon, alumina, or glass, they concluded that surface polarity is responsible for tubule orientation. They also demonstrated an increase in the hydrophobicity of the HOPG surface covered with tubules by measuring the contact

• angle, which increased from 88° (freshly wax covered surface) to 129° after 14 days. A more recent study by the same group [6] demonstrated a number of factors which affect the self-assembly of nonacosan-10-ol molecules on various substrates. By thermal vapor deposition of the wax molecules (in order to

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

• discovered interesting new wetting characteristics of the surface of the flower of the wild pansy (Viola tricolor). This surface is superhydrophobic with a static contact angle of 169° and very low hysteresis, i.e., the petal effect does not exist and water droplets roll-off as from a lotus (Nelumbo nucifera

• (“Lotus effect”) [4][5][6] or cause air retention under water (“Salvinia effect”) [7][8]. Superhydrophobic, self-cleaning surfaces possess a static contact angle (CA) equal to or above 150°, and a low hysteresis angle, where water droplets roll-off at surface inclinations equal to or below 10° [6][9]. One

• solid in contact with the liquid and is dimensionless. Further important factors in surface wetting are the static contact angle hysteresis (CAH) and the tilt angle (TA). The CAH describes the difference between the advancing and receding CAs of a moving droplet, or of one increasing and decreasing in

Sorting of droplets by migration on structured surfaces

• Wilfried Konrad and
• Anita Roth-Nebelsick

Beilstein J. Nanotechnol. 2011, 2, 215–221, doi:10.3762/bjnano.2.25

• is a topic of interest for various applications. It is well known that liquid droplets move towards areas of minimum contact angle if placed on a flat solid surface exhibiting a gradient of contact angle. This effect can be utilised for droplet manipulation. In this contribution we describe how

• droplet. If the value of the contact angle is fixed and lies within a certain interval, then droplets sitting initially on a cone can gain energy by moving to adjacent cones. Conclusion: Surfaces covered with cone-shaped protrusions or cavities may be devised for constructing “band-conveyors” for droplets

• . In our approach, it is essentially the surface structure which is varied, not the contact angle. It may be speculated that suitably patterned surfaces are also utilised in biological surfaces where a large variety of ornamentations and surface structuring are often observed. Keywords: microdroplets

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

• and any macroscopic geometric parameter of the scales in the three investigated species (data not shown). Thus, either material properties or the micro ornamentation of the scales induce the high wettability. Contact angle and microscopic morphology To quantify the wetting properties we attempted to

• measure the apparent contact angle. Measuring the apparent contact angle of the non-moisture harvesting lizards such as S. scincus was simply performed by using a commercially available contact angle meter and gave an apparent contact angle of 76 ± 5° (n = 7) on the dorsal and 59 ± 7° (n = 7) on the

• the liquid (Figure 4A). While on the inner side of the scale a small meniscus was formed suggesting an apparent contact angle of about 60° to 70°, as measured by hand from the photo, the meniscus on the outer side is much higher forming an apparent contact angle of below 10°, rendering this surface

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

• repellency is the measurement of the static contact angle by the ‘sessile drop’ method. Neinhuis and Barthlott (1997) [7] for example, measured contact angles on the lotus leaf of 162°, which are among the highest of the compared species, but many other (43%) of the tested superhydrophobic plants also showed

• contact angles between 160 and 163°. Even some species with flat epidermis cells but with a dense layer of epicuticular wax crystals, such as Brassica oleracea or some Eucalyptus species, can exhibit contact angles >160°. Thus, the contact angle alone is not suitable for a differentiated comparison of

• superhydrophobic samples. Other values such as contact angle hysteresis or roll-off (tilting) angle show more clearly the differences between the species. Mockenhaupt et al. (2008) [8] compared the tilting angles and the stability of the superhydrophobicity of various plants under moisture condensation conditions

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

• substrates, droplet wrapping can occur for all liquids, including those for which the Young’s law contact angle (defined by the interfacial tensions) is greater than 90° and which would therefore normally be considered relatively hydrophobic. However, consideration of the balance between bending and

• wrapping and relate it to the same transition condition known to apply to superhydrophobic surfaces. The results are given for both droplets being wrapped by thin ribbons and for solid grains encapsulating droplets to form liquid marbles. Keywords: capillary origami; Cassie; contact angle

• . Depositing a small droplet onto a smooth substrate and measuring the contact angle in side-profile view gives the contact angle, θ, which is assumed (to within contact angle hysteresis) to approximate to the Young’s law value, θe, given by the interfacial tensions, i.e., cosθe = (γSV − γSL)/γLV where the γij

Superhydrophobic surfaces of the water bug Notonecta glauca: a model for friction reduction and air retention

• Petra Ditsche-Kuru,
• Erik S. Schneider,
• Jan-Erik Melskotte,
• Martin Brede,
• Alfred Leder and
• Wilhelm Barthlott

Beilstein J. Nanotechnol. 2011, 2, 137–144, doi:10.3762/bjnano.2.17

• surface parameters, SEM images of 10 areas of each of the 6 investigated individuals were analysed with the digital image processing software ImageJ. Contact angle (CA) measurements. To characterise the wetting behaviour of the biological surfaces, contact (CA) and tilting angle (TA) measurements were

• performed with a DataPhysics Contact Angle System OCA, TBU 90 E (DataPhysics GmbH, Filderstadt, Germany), which was operated by the software SCR 20 (DataPhysics). CA measurements were performed with the “needle-in-drop” method by application of 5 µL droplets of pure water. CA and TA were measured for ten

Biomimetics inspired surfaces for drag reduction and oleophobicity/philicity

• Bharat Bhushan

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

• a high contact angle and low contact angle hysteresis also exhibit low adhesion and drag reduction for fluid flow. An aquatic animal, such as a shark, is another model from nature for the reduction of drag in fluid flow. The artificial surfaces inspired from the shark skin and lotus leaf have been

• . Static contact angle and contact angle hysteresis of a lotus leaf are about 164° and 3°, respectively [12][13]. The water droplets on the leaves remove any contaminant particles from their surfaces when they roll off, leading to self-cleaning [5] and show low adhesive force [14][15][16]. Natural

• . SEM micrographs show an overview (left column), a detail in higher magnification (middle column), and a large magnification of the created flat wax layers and tubules nanostructures (right column). Table 1 summarizes the static contact angle and contact angle hysteresis measured on shark skin replica