scholarly journals Superhydrophobic Fabrics with Mechanical Durability Prepared by a Two-Step Plasma Processing Method

Coatings ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 351 ◽  
Author(s):  
Kosmas Ellinas ◽  
Angeliki Tserepi ◽  
Evangelos Gogolides
Keyword(s):  
Surface Energy ◽  
Plasma Deposition ◽  
Contact Angle Hysteresis ◽  
Plasma Processing ◽  
High Water ◽  
Contact Angles ◽  
Processing Method ◽  
Static Contact ◽  
Mechanical Durability ◽  
Fabric Surface

Most studies on superhydrophobic fabrics focus on their realization using additive manufacturing (bottom-up) techniques. Here we present the direct modification of three different fabrics using a plasma-based method to obtain anti-adhesive and self-cleaning properties. A two-step plasma processing method is used: (a) for the creation of micro-nanoscale features on the fabric surface (plasma texturing step) and (b) the minimization of the fabric surface energy (by a short plasma deposition step of a very thin, low surface energy layer). The entire process takes only 14 min and all fabrics after processing exhibit high water static contact angles (WSCA > 150°), low contact angle hysteresis (CAH < 7°) and advantageous mechanical durability against hand-rumpling. The method is simple and generic, and it can be therefore expanded to other polymeric fabrics (i.e., acrylic) in addition to polyester, without any limitation rising from the weaving characteristics of the fabric or the starting nature of the material (i.e., hydrophobic or hydrophilic).

scholarly journals Biomimetic Approach for the Elaboration of Highly Hydrophobic Surfaces: Study of the Links between Morphology and Wettability

Biomimetics ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 38
Author(s):  
Quentin Legrand ◽  
Stephane Benayoun ◽  
Stephane Valette
Keyword(s):  
Contact Angle ◽  
Ginkgo Biloba ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Textured Surfaces ◽  
Replication Process ◽  
Wetting Behavior ◽  
Static Contact ◽  
Biomimetic Approach ◽  
Highly Hydrophobic

This investigation of morphology-wetting links was performed using a biomimetic approach. Three natural leaves’ surfaces were studied: two bamboo varieties and Ginkgo Biloba. Multiscale surface topographies were analyzed by SEM observations, FFT, and Gaussian filtering. A PDMS replicating protocol of natural surfaces was proposed in order to study the purely morphological contribution to wetting. High static contact angles, close to 135∘, were measured on PDMS replicated surfaces. Compared to flat PDMS, the increase in static contact angle due to purely morphological contribution was around 20∘. Such an increase in contact angle was obtained despite loss of the nanometric scale during the replication process. Moreover, a significant decrease of the hysteresis contact angle was measured on PDMS replicas. The value of the contact angle hysteresis moved from 40∘ for flat PDMS to less than 10∘ for textured replicated surfaces. The wetting behavior of multiscale textured surfaces was then studied in the frame of the Wenzel and Cassie–Baxter models. Whereas the classical laws made it possible to describe the wetting behavior of the ginkgo biloba replications, a hierarchical model was developed to depict the wetting behavior of both bamboo species.

The Surface Modification with Fluorocarbon Thin Films for the Prevention of Stiction in Mems

1998 ◽  
Vol 518 ◽  
Author(s):  
Sang-Ho Lee ◽  
Myong-Jong Kwon ◽  
Jin-Goo Park ◽  
Yong-Kweon Kim ◽  
Hyung-Jae Shin
Keyword(s):  
Contact Angle ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Fluorocarbon Films ◽  
Perfluorodecanoic Acid ◽  
Large Hysteresis ◽  
Static Contact ◽  
Receding Contact ◽  
Highly Hydrophobic ◽  
Receding Contact Angle

AbstractHighly hydrophobic fluorocarbon films were prepared by the vapor phase (VP) deposition method in a vacuum chamber using both liquid (3M's FC40, FC722) and solid sources (perfluorodecanoic acid (CF3(CF2)8COOH), perfluorododecane (C12F26)) on Al, Si and oxide coated wafers. The highest static contact angles of water were measured on films deposited on aluminum substrate. But relatively lower contact angles were obtained on the films on Si and oxide wafers. The advancing and receding contact angle analysis using a captive drop method showed a large contact angle hysteresis (ΔH) on the VP deposited fluorocarbon films. AFM study showed poor film coverage on the surface with large hysteresis. FTIR-ATR analysis positively revealed the stretching band of CF2 groups on the VP deposited substrates. The thermal stability of films was measured at 150°C in air and nitrogen atmospheres as a function of time. The rapid decrease of contact angles was observed on VP deposited FC and PFDA films in air. However, no decrease of contact angle on them was observed in N2.

Fabrication and Wettability Analysis of Hydrophobic Stainless Steel Surfaces With Microscale Structures From Nanosecond Laser Machining

2018 ◽  
Vol 6 (3) ◽  
Author(s):  
Cong Cui ◽  
Xili Duan ◽  
Brandon Collier ◽  
Kristin M. Poduska
Keyword(s):  
Stainless Steel ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Surface Structures ◽  
Laser Machining ◽  
Nanosecond Laser ◽  
Static Contact ◽  
Submicron Structures ◽  
Steel Surfaces ◽  
Hierarchical Multiscale

In this work, nanosecond laser machining is used to fabricate hydrophobic 17-4 PH stainless steel surfaces with microscale and submicron structures. Four surface structures were designed, with microscale channels and pillars (100 μm pitch size) of uniform heights (100 μm) or alternating heights (between 100 μm and 50 μm). During fabrication, the high-power laser beams also created submicron features on top of the microscale ones, leading to hierarchical, multiscale surface structures. Detailed wettability analysis was conducted on the fabricated samples. Measured static contact angles of water on these surfaces are over 130 deg without any coating, compared to ∼70 deg on the original steel surface before laser machining. Slightly lower contact angle hysteresis was also observed on the laser machined surfaces. Overall, these results agree with a simple Cassie–Baxter model for wetting that assumes only fractional surface area contact between the droplet and the surface. This work demonstrates that steel surfaces machined with relatively inexpensive nanosecond laser can achieve excellent hydrophobicity even with simple microstructural designs.

Superhydrophobic Surfaces Properties for Anti-Icing

2011 ◽  
Author(s):  
Mohammad Amin Sarshar ◽  
Christopher Swarctz ◽  
Scott Hunter ◽  
John Simpson ◽  
Chang-Hwan Choi
Keyword(s):  
Contact Angle ◽  
Wind Tunnel ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Superhydrophobic Surfaces ◽  
Ice Formation ◽  
Flow Conditions ◽  
Water Droplets ◽  
Dynamic Flow ◽  
Static Contact

In this paper, the iceophobic properties of superhydrophobic surfaces are compared to those of uncoated aluminum and steel plate surfaces as investigated under dynamic flow conditions by using a closed loop low-temperature wind tunnel. Superhydrophobic surfaces were prepared at the Oak Ridge National Laboratory by coating aluminum and steel plates with nano-structured hydrophobic particles. The contact angle and contact angle hysteresis measured for these surfaces ranged from 165–170° and 1–8°, respectively. The superhydrophobic plates along with uncoated control ones were exposed to an air flow of 12 m/s and 20°F with micron-sized water droplets in the icing wind tunnel and the ice formation and accretion were probed by using high speed cameras for 90 seconds. Results show that the developed superhydrophobic coatings significantly delay the ice formation and accretion even with the impingement of accelerated super-cooled water droplets, but there is a time scale for this phenomenon which has a clear relation with contact angle hysteresis of the samples. Among the different superhydrophobic coating samples, the plate having the lowest contact angle hysteresis showed the most pronounced iceophobic effects, while the correlation between static contact angles and the iceophobic effects was not evident. The results suggest that the key parameter for designing iceophobic surfaces is to retain a low contact angle hysteresis, rather than to have only a low contact angle, which can result in more efficient anti-icing properties in dynamic flow conditions.

scholarly journals Thick drops climbing uphill on an oscillating substrate

2018 ◽  
Vol 840 ◽  
pp. 131-153 ◽  
Author(s):  
J. T. Bradshaw ◽  
J. Billingham
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Boundary Integral ◽  
Static Contact Angle ◽  
Rise Velocity ◽  
Contact Lines ◽  
Weakly Nonlinear ◽  
Static Contact

Experiments have shown that a liquid droplet on an inclined plane can be made to move uphill by sufficiently strong, vertical oscillations (Brunet et al., Phys. Rev. Lett., vol. 99, 2007, 144501). In this paper, we study a two-dimensional, inviscid, irrotational model of this flow, with the velocity of the contact lines a function of contact angle. We use asymptotic analysis to show that, for forcing of sufficiently small amplitude, the motion of the droplet can be separated into an odd and an even mode, and that the weakly nonlinear interaction between these modes determines whether the droplet climbs up or slides down the plane, consistent with earlier work in the limit of small contact angles (Benilov and Billingham, J. Fluid Mech. vol. 674, 2011, pp. 93–119). In this weakly nonlinear limit, we find that, as the static contact angle approaches $\unicode[STIX]{x03C0}$ (the non-wetting limit), the rise velocity of the droplet (specifically the velocity of the droplet averaged over one period of the motion) becomes a highly oscillatory function of static contact angle due to a high frequency mode that is excited by the forcing. We also solve the full nonlinear moving boundary problem numerically using a boundary integral method. We use this to study the effect of contact angle hysteresis, which we find can increase the rise velocity of the droplet, provided that it is not so large as to completely fix the contact lines. We also study a time-dependent modification of the contact line law in an attempt to reproduce the unsteady contact line dynamics observed in experiments, where the apparent contact angle is not a single-valued function of contact line velocity. After adding lag into the contact line model, we find that the rise velocity of the droplet is significantly affected, and that larger rise velocities are possible.

scholarly journals Multifunctional aluminium surfaces – Laser-structured micropatterns with ice-repellent, superhydrophobic and easy-to-clean properties

2020 ◽  
Vol 326 ◽  
pp. 04005
Author(s):  
Stephan Milles ◽  
Marcos Soldera ◽  
Bogdan Voisiat ◽  
Andrés Fabián Lasagni
Keyword(s):  
Contact Angle ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Pure Aluminium ◽  
Sliding Angle ◽  
Water Contact ◽  
Static Contact ◽  
Direct Laser ◽  
Periodic Microstructures ◽  
Time Required

In this work, the fabrication of multifunctional periodic microstructures on pure aluminium is presented. Three different geometries were fabricated with feature sizes ranging between 7 µm and 50 µm by using laser-based microstructuring methods. In detail, nanosecond pulsed direct laser writing and picosecond pulsed direct laser interference patterning were used with infrared laser radiation. The wetting characteristics of these structures were investigated performing static water contact angle measurements as well as by measuring the contact angle hysteresis and the sliding angle. The final wetting results show constant static contact angles above 150°, permitting the water droplets to roll off the substrate as well as collecting contamination at the same time. This self-cleaning effect led to a reduction of up to 94% of the spread of 1 µm sized manganese oxide particles. In addition, the freezing time required for droplets laying on the patterned surfaces was increased nearly by 300% at a temperature of 20 °C below zero. Finally, the results are compared to finite element simulations of heat transfer.

scholarly journals Producing superhydrophobic/oleophobic coatings on Cultural Heritage building materials

2018 ◽  
Vol 90 (3) ◽  
pp. 551-561 ◽  
Author(s):  
Maria J. Mosquera ◽  
Luis A.M. Carrascosa ◽  
Nabil Badreldin
Keyword(s):  
Contact Angle ◽  
Surface Energy ◽  
Cultural Heritage ◽  
Building Materials ◽  
Contact Angle Hysteresis ◽  
Simple Method ◽  
Cleaning Performance ◽  
Static Contact ◽  
Heritage Building ◽  
Building Surfaces

AbstractWater is the main vehicle of decay agents in Cultural Heritage building materials exposed to weathering. In this work, a simple method to produce superhydrophobic/oleophobic coatings building materials, including under outdoors conditions, has been developed. In addition, a study of the behavior of the developed coatings on different substrates (limestone, granite, concrete and wood) is reported. The addition of 40 nm-SiO2nanoparticles to a fluoroalkylsilane reduces surface energy and produces a Cassie-Baxter surface in all the materials evaluated. It promotes high static contact angle values of around 160°, and a contact angle hysteresis of around 3°, giving rise to repellence. The building surfaces also demonstrate an excellent self-cleaning performance. The coatings maintain the building materials esthetics as required in the Cultural Heritage field. Finally, the coating presents a long-lasting performance due to condensation reactions producing effective grafting to the four building materials evaluated.

scholarly journals Self-Stratifying Particulate Coating for Robust Superhydrophobic and Latex-Repellent Surface

2020 ◽  
Vol 8 (3) ◽  
pp. 1111-1117
Keyword(s):  
Surface Roughness ◽  
Surface Energy ◽  
Film Surface ◽  
Contact Angles ◽  
Polymer Binder ◽  
Drying Temperature ◽  
Low Surface Energy ◽  
Mechanical Durability ◽  
Film Substrate ◽  
Convection Dominated

A technique for preparing superhydrophobic and natural latex-repellent surface requires at least two fabrication components: surface roughness, and surface layer with low free energy. Here, multiscale surface roughness in micro-/nanoscales with low surface energy can be simultaneously achieved through the deposition of fluoroalkyl-functionalized silica aggregates. However, the mechanical durability of such film remains problematic. Therefore, third component such as polymer binder was incorporated carefully to improve adhesion between film-substrate interface without deteriorating surface roughness and surface energy. In this work, we employed self-stratifying coating technique to induce vertical phase separation between particles and polymer during film drying, such that the silica aggregates densely accumulated on the top surface, while polymer binder concentrated near the film bottom. The governing transports during film stratification process involve diffusion and convection driven by evaporation. Thus, this research focused on the effect of drying temperature and evaporation rate on the anti-wetting performance of the coating. The results showed that the liquid-repellent properties of the surface improve with increasing drying temperature, indicating the convection-dominated transport that induced substantial particle trap at the film surface. With polymer binder added, the coatings still showed decent superhydrophobic and natural latex-repellent properties with maximum contact angles 166.4°±0.6° and 157.5°±0.5°, as well as minimum sliding angles 2.7°±0.3° and 2.9°±0.2° for water and natural latex respectively. Also, AFM result revealed that significant surface roughness of 581 ± 18 nm was still achievable even at high blending mass ratio of polymer binder up to half of the silica weight.

Functionalization of technical textile tapes

2018 ◽  
Vol 2 (89) ◽  
pp. 72-84
Author(s):  
W. Urbaniak-Domagała ◽  
E. Kobierska
Keyword(s):  
Hydrophobic Effect ◽  
Hierarchical Structures ◽  
High Water ◽  
Contact Angles ◽  
Slow Increase ◽  
Water Contact ◽  
Reduced Pressure ◽  
Dry Process ◽  
Hydrophobic Barrier ◽  
Fabric Surface

Purpose: The aim of the study was to deposit a hydrophobic barrier coating on technical tapes in order to protect them from water and to test and assess the obtained products. Design/methodology/approach: The coatings were deposited on elastic, textile substrates using PACVD of hexamethyldisiloxane vapours with an RF commercial plasma system under reduced pressure. Findings: The coatings increased the hydrophobicity of the technical tapes, which was confirmed by high water contact angles and reduced water sorption by the tape. The polymerization of the monomer vapour plasma was achieved without carrier gas. With a relatively slow increase in the deposition, rough coatings were obtained on a submicroscopic level, as opposed to the commonly produced smooth ppHMDSO coatings. This rough character enhanced the hydrophobicity of the surface according to the Wetzel or Cassie models. The modification processes did not significantly affect the basic mechanical properties of the tapes, such as Young’s modulus and tensile strength. The ppHMDSO coatings are resistant to aging and mechanical wear and retain their hydrophobic barrier properties. Research limitations/implications: The quantitative assessment of the wettability of a substrate with a rough surface is difficult and often ambiguous. This element of physicochemical metrology is wide open for innovation. Practical implications: The use of this plasma technique to make textile barrier products shows several merits, such as an economically justifiable, pro-ecological and dry process. The hydrophobicity of the textile substrates can also be obtained using other monomers. Originality/value: The formation of local hierarchical structures on the top layer of the fabric surface enhance the hydrophobic effect.

Influence of surface structure on wetting of coated offset papers

Holzforschung ◽  
2007 ◽  
Vol 61 (5) ◽  
pp. 516-522 ◽  
Author(s):  
Carl-Mikael Tåg ◽  
Mikael Järn ◽  
Björn Granqvist ◽  
Joakim Järnström ◽  
Jouko Peltonen ◽  
...  
Keyword(s):  
Surface Energy ◽  
Contact Angles ◽  
Energy Calculation ◽  
Print Quality ◽  
Force Microscopy ◽  
Angle Measurements ◽  
Static Contact ◽  
Wetting Process ◽  
Energy Components ◽  
Calculation Models

Abstract To obtain more knowledge of the properties affecting print quality and adhesion characteristics in the printing process, attention has been directed to the nature of surface energy. The aim was to compare different surface-energy calculation models and to investigate the influence of surface roughness on wetting of coated offset papers. The wetting process was studied by static contact angle measurements using a series of reference liquids. Topographical characterization was carried out using atomic force microscopy. Surface energy components were determined using different calculation models. The determination can be considerably simplified using a mono-monopolar model, which has been proven in previous studies. The surface energy components were derived from both apparent and topography-corrected contact angles. The surface topography had a significant effect on wetting of the samples studied.

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