Preparation of micro/nanopatterned gelatins crosslinked with genipin for biocompatible dental implants

• Reika Makita,
• Tsukasa Akasaka,
• Seiichi Tamagawa,
• Yasuhiro Yoshida,
• Saori Miyata,
• Hirofumi Miyaji and
• Tsutomu Sugaya

Beilstein J. Nanotechnol. 2018, 9, 1735–1754, doi:10.3762/bjnano.9.165

• not in agreement with the large cell area seen on our gelatin pillars. PLLA pillar surfaces are hydrophobic because their contact angle is about 85°, whereas in contrast, our gelatin pillars are highly hydrophilic. For this reason, cells grown on gelatin pillars are more likely to generate a larger

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

• . Measurements of the interfacial contact angle were made on the as-fabricated amorphous membrane and after pore widening with a range of pore diameters from 25 to 100 nm. The possible applications of PAMs for various membrane technologies is shown. Keywords: interfacial contact angle; membranes; porous anodic

• the topological and technological characteristics on the resulting PAMs. The investigation of the wetting properties of PAM surfaces (outer and inner) was performed by measuring the interfacial contact angle (ICA). In our work, we show that with the control of morphology-dependent wettability of PAM

• ., PAM, nanochannel alumina NCA templates, Anodisc TM 25, Whatman Plc.) and domestically fabricated (in-house manufactured) PAMs. The degree of PAM hydrophilicity was determined by measuring the interfacial contact angle (ICA), θ, by the recumbent drop method [33]. To do this, a drop of distilled water

Nanoscale mapping of dielectric properties based on surface adhesion force measurements

• Ying Wang,
• Yue Shen,
• Xingya Wang,
• Zhiwei Shen,
• Bin Li,
• Jun Hu and
• Yi Zhang

Beilstein J. Nanotechnol. 2018, 9, 900–906, doi:10.3762/bjnano.9.84

• liquid interfacial tension, θ0 is the contact angle at zero external voltage, and d, εr and ε0 are the thickness, relative permittivity of the dielectric layer, and the absolute dielectric permittivity of vacuum, respectively. Hence, the adhesion force between the AFM tip and the sample is affected by

• both of the wetting and dielectric properties of the sample. Based on this principle, a quantitative analysis on the dielectric constant of macroscopic film has been realized by measuring the surface–water contact angle and adhesion force between the dielectric layer and a biased AFM tip [38]. Recently

Facile chemical routes to mesoporous silver substrates for SERS analysis

• Elina A. Tastekova,
• Alexander Y. Polyakov,
• Anastasia E. Goldt,
• Alexander V. Sidorov,
• Alexandra A. Oshmyanskaya,
• Irina V. Sukhorukova,
• Dmitry V. Shtansky,
• Wolgang Grünert and
• Anastasia V. Grigorieva

Beilstein J. Nanotechnol. 2018, 9, 880–889, doi:10.3762/bjnano.9.82

• absorbance spectrum, replotted from total reflection data, is presented in Figure 3. The water contact angle was measured for the reduced and initial Ag2O films. The contact angle for water aliquots of 0.5 µL was of 20 ± 5° for six Ag2O films obtained using standard methods with a net 150 nm thick silver

• film oxidation in vapors of concentric nitric acid. The average contact angle value for reduced films varied depending on the roughness of the film while the presence of PVP molecules in the reaction media was less significantly influenced. For uniform nanostructured reduced films, the contact angle

• increased up to 59 ± 11° in both cases. For comparison, the contact angle value for defective (with small scratches) films were 52 ± 15°. The mesoporous silver microcubes and mp-Ag/Ag films prepared employing PVP and a ten-fold excess of NaBH4 were compared as promising materials for SERS chips. The Raman

Effect of microtrichia on the interlocking mechanism in the Asian ladybeetle, Harmonia axyridis (Coleoptera: Coccinellidae)

• Jiyu Sun,
• Chao Liu,
• Bharat Bhushan,
• Wei Wu and
• Jin Tong

Beilstein J. Nanotechnol. 2018, 9, 812–823, doi:10.3762/bjnano.9.75

• , Vision Research Inc., USA) at 300 frames/s. Contact angle The surface hydrophobicity was measured for both the dorsal side (DS) and the ventral side (VS). There are many veins in the wing base, resulting in an uneven surface that affects measurements. Therefore, we selected the posterior margin, which is

• relatively flat. The contact angles (CAs) of the three main fields of the posterior margin of the hindwing were measured, namely, contact angle testing regions I–III (CAI–CAIII) (Figure 2a), using the contact angle system (OCA20, Dataphysics Instruments GmbH, Germany), and tests were performed using the

• angular orientation was measured for approximately 20–30 microtrichia in each position, and the mean values were used. Contact angle of the hindwings To further understand the hydrophobic function of H. axyridis hindwings, a standard-type contact angle meter was used to quantify their anti-wetting

Ultralight super-hydrophobic carbon aerogels based on cellulose nanofibers/poly(vinyl alcohol)/graphene oxide (CNFs/PVA/GO) for highly effective oil–water separation

• Zhaoyang Xu,
• Huan Zhou,
• Sicong Tan,
• Xiangdong Jiang,
• Weibing Wu,
• Jiangtao Shi and
• Peng Chen

Beilstein J. Nanotechnol. 2018, 9, 508–519, doi:10.3762/bjnano.9.49

• ) was synthesized by a facile and green approach. The resulting CNF/PVA/GO aerogels were synthesized through an environmentally friendly freeze-drying process and then carbonized to yield CNF/PVA/GO carbon aerogels with low density (18.41 mg cm−3), high porosity (98.98%), a water contact angle of 156

• that the water contact angles are affected significantly by the hydrophilic functional groups on the aerogel surfaces. After the carbonization treatment, the hydrophilic functional groups on the carbon aerogel surfaces disappeared. As shown in Figure 7, the water contact angle of the carbon aerogel was

• found to be approximately 156°. It is found that the water contact angle on the external surfaces do not show any obvious change with time. These results further confirm the excellent super-hydrophobicity stability of the carbon aerogels examined in this work. Besides, the porous skeleton of the CNF/PVA

Kinetics of solvent supported tubule formation of Lotus (Nelumbo nucifera) wax on highly oriented pyrolytic graphite (HOPG) investigated by atomic force microscopy

• Sujit Kumar Dora,
• Kerstin Koch,
• Wilhelm Barthlott and
• Klaus Wandelt

Beilstein J. Nanotechnol. 2018, 9, 468–481, doi:10.3762/bjnano.9.45

• the continuous incorporation of wax molecules. The crystallization process was observed up to 4 hours before the increasing height of the tubules led to experimental artifacts. In addition, they also observed an increase in hydrophobicity of the wax structures, demonstrated by an increase in contact

• angle from 88° to 129° after 14 days of wax recrystallization on HOPG. A more recent surface scientific approach by Koch et al. [22] demonstrated a spiral growth mechanism of tubule formation. The effect of substrate polarity on tubule growth was also demonstrated by showing upright oriented tubules on

Bombyx mori silk/titania/gold hybrid materials for photocatalytic water splitting: combining renewable raw materials with clean fuels

• Stefanie Krüger,
• Michael Schwarze,
• Otto Baumann,
• Christina Günter,
• Michael Bruns,
• Christian Kübel,
• Dorothée Vinga Szabó,
• Rafael Meinusch,
• Verónica de Zea Bermudez and
• Andreas Taubert

Beilstein J. Nanotechnol. 2018, 9, 187–204, doi:10.3762/bjnano.9.21

• instrument software (Sol.I.D.) was employed for calculations of results supporting Washburn’s equation. A mercury surface tension of 0.48 N/m and a contact angle of intruded mercury of 140° were assumed. Reflection solid-state UV–vis spectrometry was done on a Perkin-Elmer (PE) Lambda 950 UV–vis spectrometer

Robust nanobubble and nanodroplet segmentation in atomic force microscope images using the spherical Hough transform

• Yuliang Wang,
• Tongda Lu,
• Xiaolai Li,
• Shuai Ren and
• Shusheng Bi

Beilstein J. Nanotechnol. 2017, 8, 2572–2582, doi:10.3762/bjnano.8.257

• NBs and NDs, such as contact angle, size, density, and volume, is generally required in their studies. For example, in the study of wettability properties of NDs, contact angle is generally applied [17][18]. In the study of influence factors for NB/ND formation, such as temperature [19][20][21] and

• which are as close as possible to their actual boundaries. Through segmentation, their size, density, contact angle and even volume can be extracted. The major difficulty in automated NB/ND segmentation is the uneven background of AFM images, either because of the thermal drift and hysteresis of AFM

• nanodroplets Both NBs and NDs have a spherical-cap shape. To facilitate the morphological characterization, some parameters are introduced in this paper, as shown in Figure 3. In the figure, H refers to the height of a NB or ND, D and θ are the width and contact angle, respectively. After segmentation, H and D

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

• selected. Contact angle and contact angle hysteresis measurements Surface wettability can affect boundary slip. In order to decouple the individual effects of roughness and wettability on slip, the contact angle (CA) and contact angle hysteresis (CAH) have to be constant. CA and CAH were measured by using

• nanoparticles coalesce to larger agglomerates and enhance the amplitude parameters of the surfaces. The average width of the roughness pitch (AR) is kept constant at 2000 ± 100 nm. Contact angle and contact angle hysteresis Table 3 shows the CAs and CAHs of hexadecane and ethylene glycol on the superoleophilic

Strategy to discover full-length amyloid-beta peptide ligands using high-efficiency microarray technology

• Clelia Galati,
• Natalia Spinella,
• Lucio Renna,
• Danilo Milardi,
• Francesco Attanasio,
• Michele Francesco Maria Sciacca and
• Corrado Bongiorno

Beilstein J. Nanotechnol. 2017, 8, 2446–2453, doi:10.3762/bjnano.8.243

• functionalized slides only. The fluorescence intensity of each spot defines regular circles matched with the spotting scheme. This spot morphology results from the optimal wettability of the epoxysilane slide (see Figure S1 in Supporting Information File 1 for contact angle measurements) that prevents the

• spreading and coalescence of the spots. As far as reference slide is concerned, in order to minimize effects due to different wettability, stored slide with similar contact angle and very low fluorescence background were used. The background level of the epoxysilane slide does not essentially increase after

• evaluated by contact angle measurements. Analysis was conducted on the dried slide immediately after the silanization process using a CAM KSV instrument operating in static mode and located in a class-1000 clean room. Drops of Millipore water were dispensed with a volume of 1 μL on at least five

Au nanostructure fabrication by pulsed laser deposition in open air: Influence of the deposition geometry

• Rumen G. Nikov,
• Anna Og. Dikovska,
• Nikolay N. Nedyalkov,
• Georgi V. Avdeev and
• Petar A. Atanasov

Beilstein J. Nanotechnol. 2017, 8, 2438–2445, doi:10.3762/bjnano.8.242

• Optics, HR 4000). The resistivity of the samples was measured using the four-point probe method. The electrical response of the samples was studied during irradiation by a 30 mW CW laser operating at 785 nm. Also, the hydrophobic properties of the samples were tested by measuring the contact angle of a

• nanostructures produced in this study focused our attention on their hydrophobic behavior. Table 2 presents the contact angle for the samples obtained at different deposition geometries, together with the images of the droplets formed on the sample surface. All samples present a hydrophobic behavior, except for

• the one deposited using geometry 1, where the contact angle θ is less than 90°. The most pronounced hydrophobicity was observed for the structures shown in Figure 4b,c, where the contact angle was greater than 120°. It is known that the structures consisting of such nanocolumnar arrays possess good

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

• epicuticular wax showed that 1-triacontanol (C30H61OH) is the main wax component of the soybean leaf surfaces. A water contact angle (CA) of 162.4° (σ = 3.6°) and tilting angle (TA) of 20.9° (σ = 10.0°) were found. Adherence of pure water droplets on the superhydrophobic leaves is supported by the hydrophilic

• interfaces, usually termed wettability, can be measured as a static or dynamic contact angle [23]. Surfaces on which a water droplet forms a spherical shape are characterized by a high contact angle (CA). Plant surfaces with high contact angles above 150° are termed superhydrophobic [24][25]. Wettable

• surfaces, on which an applied drop of water tends to spread, have a low or zero-degree contact angle. Whether droplets adhere on a surface or not is described by the contact angle hysteresis (CAH). It is measured as the difference between the advancing and receding angles of a droplet (CAH = CAadv − CArec

Photobleaching of YOYO-1 in super-resolution single DNA fluorescence imaging

• Joseph R. Pyle and
• Jixin Chen

Beilstein J. Nanotechnol. 2017, 8, 2296–2306, doi:10.3762/bjnano.8.229

• , immobilize, and image a single DNA using the established protocol and our fluorescence microscope. Glass cover slip substrates modified with amino silane are used to immobilize single DNA molecules (Figure 3). After surface modification, the water contact angle for the cover slips is 48 ± 4° which is

• immobilization, giving a water contact angle of 48 ± 4°. (a) A single DNA molecule (top), the mask used (middle), and overlay (bottom) to select the DNA and filter the other events (the arrow). (b) The intensity (total photocounts) per micrometer of single DNA molecules as a function of laser power density. The

A comparative study of the nanoscale and macroscale tribological attributes of alumina and stainless steel surfaces immersed in aqueous suspensions of positively or negatively charged nanodiamonds

• Colin K. Curtis,
• Antonin Marek,
• Alex I. Smirnov and
• Jacqueline Krim

Beilstein J. Nanotechnol. 2017, 8, 2045–2059, doi:10.3762/bjnano.8.205

• surface hydroxy groups determine electrostatic properties of the surface that, in turn, affect interactions of charged nanoparticles (NDs in this study) with the QCM alumina electrode. In the past Cuddy et al. employed contact angle titration to determine Isoelectric points (IEPs) for five common (QCM

Imidazolium-based ionic liquids used as additives in the nanolubrication of silicon surfaces

• Patrícia M. Amorim,
• Ana M. Ferraria,
• Rogério Colaço,
• Luís C. Branco and
• Benilde Saramago

Beilstein J. Nanotechnol. 2017, 8, 1961–1971, doi:10.3762/bjnano.8.197

• the Si surface. The reduction of the contact angle in the presence of water is more significant for the PEG+IL mixtures than for pure PEG, which suggests that in the former case the water molecules being preferentially attached to the IL anions by H-bonds have a higher tendency to concentrate at the

• %, 2 wt % and 5 wt %, which showed similar results for 2 wt % and 5 wt %. The characterization of the PEG + IL mixtures with respect to the viscosity, η, at 25 °C, water content and contact angle on the silicon surface is described in Table 2. The viscosity of the mixtures is considerably higher than

• functional groups (hydroxy or allyl), respectively, [C2OHMIM] and [AMIM], led to a slight decrease in friction. Cation [BMIM] with a longer side chain induced a significant decrease in friction, despite the fact that it presents the highest contact angle. Comparison of the DCA-based additives (Figure 5b

Application of visible-light photosensitization to form alkyl-radical-derived thin films on gold

• Rashanique D. Quarels,
• Xianglin Zhai,
• Neepa Kuruppu,
• Jenny K. Hedlund,
• Ashley A. Ellsworth,
• Amy V. Walker,
• Jayne C. Garno and
• Justin R. Ragains

Beilstein J. Nanotechnol. 2017, 8, 1863–1877, doi:10.3762/bjnano.8.187

• . Analysis with AFM demonstrated that the films are robust and resistant to mechanical force while contact angle goniometry suggests a multilayered and disordered film structure. Analysis with IRRAS, XPS, and TOF SIMS provides further insights. Keywords: atomic force microscopy; organic thin film; particle

• ), and contact angle goniometry provided additional information about the structure and composition of the films. Experimental Materials and reagents. 11-Aminoundecanoic acid (97%), N-hydroxyphthalimide (97%), N,N’-dicyclohexylcarbodiimide (99%), 4-(dimethylamino)pyridine (99%, Reagent Plus), di-tert

• blue LED irradiation) were duplicated. AFM data shown here and in the Supporting Information File 1 are representative. Procedure for preparation of samples for IRRAS and contact angle goniometry. Polycrystalline 100 nm Au-film-coated glass slides obtained from Platypus Technologies (catalog number Au

Collembola cuticles and the three-phase line tension

• Håkon Gundersen,
• Hans Petter Leinaas and
• Christian Thaulow

Beilstein J. Nanotechnol. 2017, 8, 1714–1722, doi:10.3762/bjnano.8.172

• prediction of contact angles in the observed range. The discrepancy between the contact angle predicted by simple models and those observed is especially large in the springtail Cryptopygus clavatus which changes, seasonally, from superhydrophobic to wetting without a large change in surface structure; C

• overhanging surface features does not affect the apparent contact angles predicted by the Cassie–Baxter equation for a system in the composite wetting state, but does affect the stability of the composite wetting state. The apparent contact angle of a composite wetting state is predicted by the Cassie–Baxter

• equation, which underestimates the contact angle of Collembola cuticles [5] and sub-micrometer-sized surface structures in general [16]. The Cassie–Baxter equation also fails to predict changes in contact angle without an accompanying change in surface structure, such as the seasonal change in wetting

Process-specific mechanisms of vertically oriented graphene growth in plasmas

• Subrata Ghosh,
• Shyamal R. Polaki,
• Niranjan Kumar,
• Sankarakumar Amirthapandian,
• Mohamed Kamruddin and
• Kostya (Ken) Ostrikov

Beilstein J. Nanotechnol. 2017, 8, 1658–1670, doi:10.3762/bjnano.8.166

• transmission electron microscopy (HRTEM) and Raman spectroscopy. Contact angle and electrical resistance measurements of the VGNs are carried out as well. Results and Discussion Growth and optimization Case I: Influence of growth temperature We investigated the early-stage nucleation and growth of VGNs over a

• structure and defects. Here, samples grown at 600 °C showed a (contact angle) CA of 80°, indicating hydrophilic behavior (Figure 9a). However, this value significantly increased to 134° for the sample grown at 800 °C, indicating near-superhydrophobic nature (Figure 9b). Such distinct characteristic might be

• increased intersheet spacing between VGNs. The contact angle is found to vary from 127° to 134° for the other studied samples. The improvement in hydrophobicity is significant and can be considered for many useful applications. Electrical properties The sheet resistance of VGNs was measured to study their

Surface functionalization of 3D-printed plastics via initiated chemical vapor deposition

• Christine Cheng and
• Malancha Gupta

Beilstein J. Nanotechnol. 2017, 8, 1629–1636, doi:10.3762/bjnano.8.162

• with both hydrophobic and hydrophilic polymers. Contact angle goniometry and X-ray photoelectron spectroscopy were used to characterize the functionalized surfaces. Our results can enable the use of iCVD to functionalize 3D-printed materials for a range of applications such as tissue scaffolds and

• diacrylate)) (P(HEMA-co-EGDA)) [30] onto 3D objects of a variety of shapes and sizes to study the capabilities and limitations of the iCVD process. X-ray photoelectron spectroscopy (XPS) and contact angle goniometry were used to study the surface properties before and after coating. Results and Discussion A

• underlying substrate via XPS [23]. Additionally, the relatively high water contact angle on flat PPFDA (121°) [31] compared to that on flat PLA (72.5°) [32] allows for the use of contact angle goniometry to verify polymer deposition. Substrates were printed with PLA because of its ease of printing, low cost

Deposition of exchange-coupled dinickel complexes on gold substrates utilizing ambidentate mercapto-carboxylato ligands

• Martin Börner,
• Laura Blömer,
• Marcus Kischel,
• Peter Richter,
• Georgeta Salvan,
• Dietrich R. T. Zahn,
• Pablo F. Siles,
• Maria E. N. Fuentes,
• Carlos C. B. Bufon,
• Daniel Grimm,
• Oliver G. Schmidt,
• Daniel Breite,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Nanotechnol. 2017, 8, 1375–1387, doi:10.3762/bjnano.8.139

• ) and 8 (J = +20.8 cm−1; H = −2JS1S2). The reactivity of complexes 6–8 is reminiscent of that of pure thiolato ligands, which readily chemisorb on Au surfaces as verified by contact angle, atomic force microscopy (AFM) and spectroscopic ellipsometry measurements. The large [Ni2L] tail groups, however

• “auration” of 2 and 3 with AuI sources leads to the trinuclear NiII2AuI species 4 and 5. Moreover, complexes 2 and 3 interact also with Au surfaces via Au–S and Au–P bonds without complex disintegration as established by contact angle, spectroscopic ellipsometry, atomic force microscopy (AFM), X-ray

• ). The crystal structure, reactivity features, and magnetic properties of compounds 6–8 are presented along with the results stemming from characterization of the surface assemblies by contact angle measurements, spectroscopic ellipsometry, AFM and transport measurements. To our knowledge, polynuclear

Nanotopographical control of surfaces using chemical vapor deposition processes

• Meike Koenig and
• Joerg Lahann

Beilstein J. Nanotechnol. 2017, 8, 1250–1256, doi:10.3762/bjnano.8.126

• ). The nanostructured PPX films produced exhibit a high water contact angle and the use in water droplet transport was demonstrated [42][43]. Further potential applications include biomaterial design [44] and catalytic devices [45]. Conclusion Vapor deposition polymerization techniques have been

Study of the correlation between sensing performance and surface morphology of inkjet-printed aqueous graphene-based chemiresistors for NO₂ detection

• F. Villani,
• C. Schiattarella,
• T. Polichetti,
• R. Di Capua,
• F. Loffredo,
• B. Alfano,
• M. L. Miglietta,
• E. Massera,
• L. Verdoliva and
• G. Di Francia

Beilstein J. Nanotechnol. 2017, 8, 1023–1031, doi:10.3762/bjnano.8.103

• surface tension of the prepared dispersion has been evaluated by using the contact angle equipment OCA20-Dataphysics in pendant drop configuration. The measurements have been performed under ambient conditions (21 °C, RH 50%) and the estimated value has been the result of measurements repeated five times

Vapor-phase-synthesized fluoroacrylate polymer thin films: thermal stability and structural properties

• Paul Christian and
• Anna Maria Coclite

Beilstein J. Nanotechnol. 2017, 8, 933–942, doi:10.3762/bjnano.8.95

• hysteresis between advancing and receding contact angle [14]. The advantage of cross-linking with EGDMA is the elimination of the annealing step, resulting in a cross-linked film already in the as-deposited form. The thermal stability of the thin films was evaluated by ellipsometry, Fourier transform

• the freely available software package Gwyddion [19]. The water contact angle (WCA) of the polymer films was determined by the static sessile drop method on a CAM200 contact angle analyzer (KSV Instruments, Finland). Each sample was probed on five different spots, using a droplet volume of 4 μL. In

• , indicating good stability towards temperature variation in the investigated range. Changes in the surface morphology and chemistry also affect the wettability, as evidenced by a decreasing water contact angle (WCA) upon EGDMA addition to the polymer (Figure 4a). While the PFDA homopolymer forms a highly

Investigation of growth dynamics of carbon nanotubes

• Marianna V. Kharlamova

Beilstein J. Nanotechnol. 2017, 8, 826–856, doi:10.3762/bjnano.8.85

• particle and substrate decides whether the nanotube growth will follow the tip- or base-growth mechanism [34][45]. When the interaction is weak (there is an acute contact angle between the catalytic particle and substrate), the tip-growth model is realized. When the interaction is strong (there is an

• obtuse contact angle between the particle and substrate), the base-growth model is favored [34]. The growth of MWCNTs from Fe catalyst was observed to follow either growth mechanism on different substrates. Namely, the tip-growth on SiO2 and base-growth on Ta [95]. The authors of [95] found that the

• and had smaller diameter than the particle (Figure 6a). The apex of the particle acquired a cylindrical shape, lifting the carbon cap from the particle and forming the nanotube. The growing SWCNT forced further cylindrical reshaping of the particle, which led to increasing the contact angle of the