Towards optimization of patterned superhydrophobic surfaces

Bhushan, Bharat; Nosonovsky, Michael; Jung, Yong Chae

doi:10.1098/rsif.2006.0211

Cited by 138 publications

(105 citation statements)

References 44 publications

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“…1,9,15) Studies of transition from Cassie state to Wenzel state have been carried out and some important factors, affecting the occurrence of transition, such as contact line density, energy barrier, and spacing factors have been discussed. [16][17][18][19] Moulinet and Bartolo studied the droplet equilibrium state deposited on hydrophobic rough surfaces by using the real-time 3D imaging technique for different droplet sizes. 20) Erbil and Cansoy estimated the droplet penetration between the pillars by suggesting the modified Cassie-Baxter equation based on the geometry of square and cylindrical pillar patterns.…”

Section: Introductionmentioning

confidence: 99%

Wetting Transition Characteristics on Microstructured Hydrophobic Surfaces

et al. 2010

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Hydrophobicity and wetting transition behavior of water droplets were investigated on microstructured hydrophobic rough surfaces with pillar arrays, fabricated by self-replication with hydrophobic polydimethylsiloxane(PDMS) together with the use of CNC machine. The surfaces consist of microscale pillars(diameter: 105 mm, height: 150 mm) with varying spacing-to-diameter ratio (s=d) ranging from $1:0 to $3:3. A deionized(DI) water droplet of 4.3 ml was placed on hydrophobic surfaces and contact angles(CA) were measured by the digital image processing algorithm. A wetting transition from the Cassie state to the Wenzel state was demonstrated depending on the values of s=d, from $1:81 to $2:95. In the transition regime, a partial penetration of liquid meniscus which moves downward in the groove formed by four pillar posts was observed. It was also found that the contact angle prediction using the Cassie-Baxter equation showed fairly good agreement with experimental data, whereas in the transition regime, the rapid decrease in CA was found.

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Section: Introductionmentioning

confidence: 99%

Wetting Transition Characteristics on Microstructured Hydrophobic Surfaces

et al. 2010

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“…This is hypothesized to be due to the edge effects introduced by the textured pillars. This observation correlates with the study of Bhushan et al 163 who reported the pinning of a drop at the pillar edges. If the pillars were hydrophobically functionalized to produce a smooth top surface, the pre-snap receding angles can be expected to be higher.…”

Section: Experimental Set-upsupporting

confidence: 81%

“…However, the receding angle was found to increase with larger L results reported from previous experimental and computational studies. 133,134,146,156,163 In addition, the roll-off angle of the surfaces were found to be inversely proportional to L, a relation that was in agreement with the force balance equation for a drop at an inclination prescribed by Yeh et al 133 It should be noted that these apparent angles were measured using the tilt method and acquired at the incipient of drop motion, a measurement method that is widely recognized and accepted by researchers. 164 …”

Section: Fabrication Of Textured Pillar Surfacementioning

confidence: 67%

Impinging Drops on Superhydrophobic Surfaces at Icing Conditions

Yeong

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Due to their excellent water repellent characteristics, superhydrophobic surfaces have been hypothesized to be icephobic. This is based on the premise that water droplets will be repelled from the surface before ice nucleation can occur. The icephobic nature of these surfaces provides an attractive solution to current icing problems that can occur in aerospace applications. However, significant challenges remain before anti-wetting coatings could be implemented as an effective ice mitigation tool. For example, the majority of current synthetic superhydrophobic surfaces are fragile and unable to withstand the harsh environmental conditions that are encountered by aerospace applications. In addition, their static and dynamic wettability at varying temperatures and humidity, as well as their ice-shedding performance under the impact of a super-cooled icing cloud, are not well understood.Therefore, in this dissertation, fabrication techniques for a previously developed nanocomposite surface were improved so that coatings of consistent antiwetting performance and durability could be produced. The icephobicity of this nanocomposite coating was then systematically investigated. First, an experiment was conducted to study the wettability of a water drop on the coating for a full temperature cycle (20 -3The investigation was then extended to study the impact and rebound dynamics of a iv drop on an inclined coating, at different fluid viscosities and at various temperatures (50°C to -8°C). This was followed by a study of ice adhesion strength of the coatings -cooled water droplets. The receding contact angle was discovered from these experiments to be a key parameter in controlling superhydrophobic wettability and ice adhesion. Therefore, the receding angle depinning dynamics from a superhydrophobic surface were also studied in detail at micron length scales and at microsecond temporal scales. In summary, results from this dissertation revealed the crucial parameters that govern the icing performance of a nanocomposite superhydrophobic surface.

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“…The nanostructured ZnO material was first synthesized via a simple catalystfree CVD method (Bhushan et al 2007;Wang et al 2010Wang et al , 2011. In the experiment, 2.0 g Zn powder (99.999%) was heated up to 640…”

Section: (B) Fabrication Of the Zinc Oxide Superhydrophobic Surfacementioning

confidence: 99%

“…Scientists have employed capillary force (Jiang & Kiørboe 2011;Voise et al 2011) and electrowetting (De Gennes 1985;De Mello 2001;Li & Fontelos 2003;Heikenfeld & Steckl 2005;Berthier 2008;Ko et al 2008;Lu et al 2008;Fan et al 2009;Kwon et al 2009) to manipulate such small objects. However, during the process of manipulation, the droplet is usually exposed to the environment, either liquid or air.…”

Section: Introductionmentioning

confidence: 99%

Tap dance of a water droplet

Wang

Zhao

2012

Proc. R. Soc. A.

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Electro-elasto-capillarity (EEC) is a new method of droplet encapsulation controlled by an electric field. In this paper, we report some experiments, for the first time, to realize EEC under a dynamic electric field, showing the progress of electrowetting on a moving substrate. We employ the combined effects of surface tension, elastic force and Coulomb force to manipulate the flexible thin film to encapsulate and release a tiny droplet in a controllable and reversible manner. An alternating current electric field is applied to actuate the droplet and film to vibrate, as if they are dancing to a melody. We measured the frequency of the droplet and the film vibration and found that it was twice the input signal; we also carried out frequency analysis experiments. The frequency-doubling phenomenon can be explained theoretically. Our findings may offer a practical method for drug encapsulation and for the actuation of microelectromechanical system devices.

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Towards optimization of patterned superhydrophobic surfaces

Cited by 138 publications

References 44 publications

Wetting Transition Characteristics on Microstructured Hydrophobic Surfaces

Wetting Transition Characteristics on Microstructured Hydrophobic Surfaces

Impinging Drops on Superhydrophobic Surfaces at Icing Conditions

Tap dance of a water droplet

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