scholarly journals Fabrication of elastic, conductive, wear-resistant superhydrophobic composite material

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Seyed Mehran Mirmohammadi ◽  
Sasha Hoshian ◽  
Ville P. Jokinen ◽  
Sami Franssila
Keyword(s):  
Contact Angle ◽  
Composite Material ◽  
Contact Angles ◽  
Wet Etching ◽  
Sliding Angle ◽  
Electrically Conductive ◽  
Wear Resistant ◽  
Nanoscale Structures ◽  
Mechanical Abrasion ◽  
Mechanical Durability

AbstractA polydimethylsiloxane (PDMS)/Cu superhydrophobic composite material is fabricated by wet etching, electroless plating, and polymer casting. The surface topography of the material emerges from hierarchical micro/nanoscale structures of etched aluminum, which are rigorously copied by plated copper. The resulting material is superhydrophobic (contact angle > 170°, sliding angle < 7° with 7 µL droplets), electrically conductive, elastic and wear resistant. The mechanical durability of both the superhydrophobicity and the metallic conductivity are the key advantages of this material. The material is robust against mechanical abrasion (1000 cycles): the contact angles were only marginally lowered, the sliding angles remained below 10°, and the material retained its superhydrophobicity. The resistivity varied from 0.7 × 10–5 Ωm (virgin) to 5 × 10–5 Ωm (1000 abrasion cycles) and 30 × 10–5 Ωm (3000 abrasion cycles). The material also underwent 10,000 cycles of stretching and bending, which led to only minor changes in superhydrophobicity and the resistivity remained below 90 × 10–5 Ωm.

Surface Topography Induced Ultrahydrophobic Behavior: Effect of Three-Phase Contact Line Topology

2006 ◽  
Author(s):  
Neeharika Anantharaju ◽  
Mahesh Panchagnula ◽  
Wayne Kimsey ◽  
Sudhakar Neti ◽  
Svetlana Tatic-Lucic
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
Anomalous Behavior ◽  
Contact Angles ◽  
Wet Etching ◽  
Surface Geometry ◽  
Wetting Behavior ◽  
Void Fractions ◽  
Three Phase ◽  
Receding Contact

The wettability of silicon surface hydrophobized using silanization reagents was studied. The advancing and receding contact angles were measured with the captive needle approach. In this approach, a drop under study was held on the hydrophobized surface with a fine needle immersed in it. The asymptotic advancing and receding angles were obtained by incrementally increasing the volume added and removed, respectively, until no change in angles was observed. The values were compared with the previously published results. Further, the wetting behavior of water droplets on periodically structured hydrophobic surfaces was investigated. The surfaces were prepared with the wet etching process and contain posts and holes of different sizes and void fractions. The surface geometry brought up a scope to study the Wenzel (filling of surface grooves) and Cassie (non filling of the surface grooves) theories and effects of surface geometry and roughness on the contact angle. Experimental data point to an anomalous behavior where the data does not obey either Wenzel or Cassie type phenomenology. This behavior is explained by an understanding of the contact line topography. The effect of contact line topography on the contact angle was thus parametrically studied. It was also inferred that, the contact angle increased with the increase in void fraction. The observations may serve as guidelines in designing surfaces with the desired wetting behavior.

A Nonlithographic Approach for Creating Unstable Hierarchical (Micro-Nano) Superhydrophobic Silicon Surfaces

2006 ◽  
Author(s):  
Ming-Fang Wang ◽  
Nithin Nraghuna ◽  
Babak Ziaie
Keyword(s):  
Contact Angle ◽  
Porous Silicon ◽  
High Current Density ◽  
Contact Angles ◽  
Wet Etching ◽  
Silicon Surfaces ◽  
Rolling Angle ◽  
Step Method ◽  
Shape Structure ◽  
P Type

In this paper, we report on an inexpensive non-lithographic approach to create superhydrophobic silicon surfaces using porous silicon technology. We have used a two-step method to create an unstable hierarchical (micro-nano) superhydrophobic silicon surface. Our technique is a unique combination of a high current density (170mA/cm2) porous silicon formation step followed by a wet etching step in BOE/HNO3. Porous silicon layers, of both n- and p-type wafers were used in these experiments. The contact and rolling angles were measured for: 1) regular porous silicon, 2) porous silicon with hierarchical fractal-shape structure, and 3) hierarchical fractal-shape porous silicon after the wet etching step. For both n- and p-type wafers, the contact angles of regular porous silicon (nonhierarchical) were around 120° with a rolling angle of 90°. With hierarchical structure, the contact angle increased to 135° and after addition wet etching, the contact angle approached 160° (superhydrophobic). Besides, after wet etching step the surface became extremely unstable showing a very low rolling angle (&lt;1°).

Fabrication of Super-Hydrophobic Film on Tinplate’s Surface by a Simple Casting Method in Material Engineering and its Application

2012 ◽  
Vol 583 ◽  
pp. 374-378
Author(s):  
Qi Long Liu ◽  
Hong Chen ◽  
Hai Yun Jiang ◽  
Ruo Mei Wu ◽  
Zhi Qing Yuan ◽  
...  
Keyword(s):  
Contact Angle ◽  
Composite Film ◽  
Hydrophobic Effect ◽  
Contact Angles ◽  
Casting Method ◽  
Sliding Angle ◽  
Water Contact ◽  
Drying Time ◽  
Practical Applications ◽  
Material Engineering

A simple, cheap and environmental double thin super-hydrophobic composite film was prepared on the surface of tinplate by a simple casting method. The contact angle and sliding angle were measured by an optical contact angle meter. And the major factors that influenced the super-hydrophobic effect of the composite film were studied in our work. The results showed that when the melting temperature was 120°C, the weight radio of PP and PP-g-MAH was 1:4, the drying time was 24h, the dosage of ethanol was 0.4ml, the composite film showed a satisfactory super-hydrophobicity and its water contact angles reached a maximum value of 156.6° while the sliding angle reached a minimum value of 2°. Because of anti-oxidation, moisture-proof and anticorrosion performance of super-hydrophobic tinplate, it has potential practical applications in packaging material engineering.

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.

Investigation of Hybrid Materials Based on Polyurethane Modified with Aliphatic Side Chains Combined with Nano-TiO2

2018 ◽  
Vol 71 (1) ◽  
pp. 47
Author(s):  
Jie Zhang ◽  
Nanjie Zhang ◽  
Quan Liu ◽  
Haojun Ren ◽  
Pengfei Li ◽  
...  
Keyword(s):  
Contact Angle ◽  
Hybrid Materials ◽  
Raw Materials ◽  
Contact Angles ◽  
Side Chains ◽  
Sliding Angle ◽  
Scanning Calorimetry ◽  
Nano Tio2 ◽  
Methylene Diphenyl Diisocyanate ◽  
Chain Extenders

In this study, methylene diphenyl diisocyanate (MDI) and polytetrahydrofuran ether diol (PTMG) were used as the raw materials for the synthesis of polyurethane (PU). 1,4-Butanediol, glyceryl monostearate, d-sorbitol tetrastearate, or d-trehalose hexastearate, all containing different amounts of aliphatic side chains, were used as the chain extenders and to introduce C18 side chains into the hard segments of PU, and hybrid materials were then fabricated by mixing PUs with nano-titanium dioxide (nano-TiO2). The effects of the different chain extenders on the surface properties of PU coatings and the hybrid materials were investigated. All the materials were characterised by NMR and FT-IR spectroscopy, differential scanning calorimetry, polarising microscopy, atomic force microscopy, scanning electron microscopy, nanoindentation, and contact angle measurements. The results indicate that incremental changes in the number of side chains decrease the degree of microscale separation from the PU coating and increase the crystallinity of the aliphatic side chains. By introducing the aliphatic side chains, the surface coating presents many tiny protrusions, which enhance the surface roughness and the contact angle. Moreover, both the nano-TiO2 and aliphatic side chain content affect the contact angle of the hybrid materials. The as-obtained superhydrophobic materials exhibit contact angles above 150° with a sliding angle below 3° and present excellent mechanical properties such as hardness and Young’s modulus. The nano-TiO2 was chemically bonded to the molecular chains of PU, resulting in superhydrophobic materials with good acidic and alkaline resistance and anti-stripping properties.

scholarly journals Influence of moisture content on the contact angle and surface tension measured on birch wood surfaces

2021 ◽  
Author(s):  
Rami Benkreif ◽  
Fatima Zohra Brahmia ◽  
Csilla Csiha
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Moisture Content ◽  
Solid Wood ◽  
Contact Angles ◽  
Surface Moisture ◽  
Wood Coatings ◽  
The Relationship ◽  
Wood Surfaces

AbstractSurface tension of solid wood surfaces affects the wettability and thus the adhesion of various adhesives and wood coatings. By measuring the contact angle of the wood, the surface tension can be calculated based on the Young-Dupré equation. Several publications have reported on contact angle measured with different test liquids, under different conditions. Results can only be compared if the test conditions are similar. While the roles of the drop volume, image shooting time etc., are widely recognized, the role of the wood surface moisture content (MC) is not evaluated in detail. In this study, the effect of wood moisture content on contact angle values, measured with distilled water and diiodomethane, on sanded birch (Betula pendula) surfaces was investigated, in order to find the relationship between them. With increasing MC from approximately 6% to 30%, increasing contact angle (decreasing surface tension) values were measured according to a logarithmic function. The function makes possible the calculation of contact angles that correspond to different MCs.

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.

scholarly journals Is contact angle a cause or an effect? – A cautionary tale

2020 ◽  
Vol 146 ◽  
pp. 03004
Author(s):  
Douglas Ruth
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Contact Angles ◽  
Two Dimensions ◽  
Experimental Results ◽  
Flow In Porous Media ◽  
Two Dimensional ◽  
Wide Range ◽  
Fluid Drop ◽  
Surrounding Fluid

The most influential parameter on the behavior of two-component flow in porous media is “wettability”. When wettability is being characterized, the most frequently used parameter is the “contact angle”. When a fluid-drop is placed on a solid surface, in the presence of a second, surrounding fluid, the fluid-fluid surface contacts the solid-surface at an angle that is typically measured through the fluid-drop. If this angle is less than 90°, the fluid in the drop is said to “wet” the surface. If this angle is greater than 90°, the surrounding fluid is said to “wet” the surface. This definition is universally accepted and appears to be scientifically justifiable, at least for a static situation where the solid surface is horizontal. Recently, this concept has been extended to characterize wettability in non-static situations using high-resolution, two-dimensional digital images of multi-component systems. Using simple thought experiments and published experimental results, many of them decades old, it will be demonstrated that contact angles are not primary parameters – their values depend on many other parameters. Using these arguments, it will be demonstrated that contact angles are not the cause of wettability behavior but the effect of wettability behavior and other parameters. The result of this is that the contact angle cannot be used as a primary indicator of wettability except in very restricted situations. Furthermore, it will be demonstrated that even for the simple case of a capillary interface in a vertical tube, attempting to use simply a two-dimensional image to determine the contact angle can result in a wide range of measured values. This observation is consistent with some published experimental results. It follows that contact angles measured in two-dimensions cannot be trusted to provide accurate values and these values should not be used to characterize the wettability of the system.

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