Factors controlling the pinning force of liquid droplets on liquid infused surfaces

Sadullah, Muhammad Subkhi; Panter, Jack R.; Kusumaatmaja, Halim

doi:10.1039/d0sm00766h

Cited by 24 publications

(18 citation statements)

References 37 publications

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“…The droplet starts to slide when the external body force is larger than the pinning force that holds the droplet on the surface. The pinning force for a droplet on the liquid-infused surface is given by the formula

where

and

are the density and volume of the droplet,

is the maximum angle of the droplet staying pinned, and

is the gravitational acceleration ( 34 ). The maximum angle of the pinned droplet,

, has the following relation to the lubricant–droplet contact angle,

, and to the areal fraction of the soft pillars over the whole lubricated surface,

.…”

Section: Resultsmentioning

confidence: 99%

Programmable droplet manipulation and wetting with soft magnetic carpets

Demirörs

Aykut

Ganzeboom

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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The ability to regulate interfacial and wetting properties is highly demanded in anti-icing, anti-biofouling, and medical and energy applications. Recent work on liquid-infused systems achieved switching wetting properties, which allow us to turn between slip and pin states. However, patterning the wetting of surfaces in a dynamic fashion still remains a challenge. In this work, we use programmable wetting to activate and propel droplets over large distances. We achieve this with liquid-infused soft magnetic carpets (SMCs) that consist of pillars that are responsive to external magnetic stimuli. Liquid-infused SMCs, which are sticky for a water droplet, become slippery upon application of a magnetic field. Application of a patterned magnetic field results in a patterned wetting on the SMC. A traveling magnetic field wave translates the patterned wetting on the substrate, which allows droplet manipulation. The droplet speed increases with an increased contact angle and with the droplet size, which offers a potential method to sort and separate droplets with respect to their contact angle or size. Furthermore, programmable control of the droplet allows us to conduct reactions by combining droplets loaded with reagents. Such an ability of conducting small-scale reactions on SMCs has the potential to be used for automated analytical testing, diagnostics, and screening, with a potential to reduce the chemical waste.

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where

and

are the density and volume of the droplet,

is the maximum angle of the droplet staying pinned, and

is the gravitational acceleration ( 34 ). The maximum angle of the pinned droplet,

, has the following relation to the lubricant–droplet contact angle,

, and to the areal fraction of the soft pillars over the whole lubricated surface,

.…”

Section: Resultsmentioning

confidence: 99%

Programmable droplet manipulation and wetting with soft magnetic carpets

Demirörs

Aykut

Ganzeboom

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

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“…As shown in Figure 4a, measuring the water CA of different lattice surfaces using the sessile drop method, the volume of the water droplet was 5, 6, and 7 μL. According to the method in the literature, 26 the radius of the solid−liquid contact interface R d is given the following equation…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…As shown in Figure a, measuring the water CA of different lattice surfaces using the sessile drop method, the volume of the water droplet was 5, 6, and 7 μL. According to the method in the literature, the radius of the solid–liquid contact interface R d is given the following equation where V is the droplet volume and θ is the CA. The calculation showed that the average solid–liquid contact interface radii of 5 and 6 μL droplets were 550.7 and 587.6 μm, respectively, which were both smaller than the lattice structure radius of 600 μm.…”

Section: Resultsmentioning

confidence: 99%

Prediction of Droplet Sliding on the Continuity of the Three-Phase Contact Line

Qiu

Chen

Di³

et al. 2021

Langmuir

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Many animals and plants have evolved wonderful hydrophobic abilities to adapt to the complex climate environment. The microstructure design of a superhydrophobic surface focuses on bionics and will be restricted by processing technology. Although certain functions can be achieved, there is a lack of unified conclusion on the wetting mechanism and a few quantitative analyses of the continuity of the three-phase contact line. Therefore, the relationship between the surface microstructure of the lattice pattern and the critical sliding angle of the water droplet in the Cassie state was investigated in this paper, and we proposed a method to quantitatively analyze the continuity of the three-phase contact line by a dimensionless length f. The results showed that the three-phase contact line was an important factor to determine the sliding performance of the droplet. The upward traction force generated by the surface tension through the force analysis on the three-phase contact line can enhance the sliding ability of the droplet on the solid surface. There was a good negative linear correlation between the critical sliding angle and dimensionless length, which provided a guiding basis for the optimal design of superhydrophobic surfaces.

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“…As the slope of the protrusion increases, the pinning force of the droplet on the surface decreases, resulting in a decrease in the CA hysteresis, which eases the rolling of the droplets. [27,28] 3.3. Analysis of the Self-Assembly Modification Mechanism of the Microstructure Surface…”

Section: Surface Wettability Analysismentioning

confidence: 99%

Preparation and Wetting Mechanism of Laser‐Etched Composite Self‐Assembled 1H,1H,2H,2H‐Perfluorodecyltriethoxysilane Superhydrophobic Surface Coating

Lan

Wang²,

Zhu

et al. 2021

Physica Status Solidi (a)

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Herein, a grid‐like microstructure is prepared on the surface of 3Cr13 stainless steel through nanosecond laser etching, and the self‐assembled 1H,1H,2H,2H‐perfluorodecyltriethoxysilane (PFDS) coating is further composited to prepare a superhydrophobic surface with a contact angle of 164° and a rolling angle of 3°. The effect of laser etching cycles on the surface microstructure and surface wettability before and after the self‐assembly is studied. With an increase in the etching cycles, a stable grid‐like microstructure is gradually formed on the surface, and subsequently, a composite structure of grooves and pits is formed. After the self‐assembly of the PFDS coating, two superhydrophobic surfaces with different wetting properties are obtained. Furthermore, as the etching cycles increase, the surface changes from a superhydrophobic and high‐adhesion state to a superhydrophobic and low‐adhesion state. The decrease in surface energy is mainly attributed to the C−F group in the PFDS molecule. The experimental results show that PFDS molecules are deposited easily in case of the convex surface, thereby facilitating the formation of superhydrophobic low‐adhesion surfaces. Finally, the superhydrophobic surface is still maintained after cumulative ultrasonic cleaning in deionized water for 75 min, showing good reusability and stability.

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Factors controlling the pinning force of liquid droplets on liquid infused surfaces

Abstract: Liquid infused surfaces with partially wetting lubricants have recently been exploited for numerous intriguing applications. Here, we study the factors that control the pinning force and the contact angle hysteresis of liquid droplets on liquid infused surfaces.

Cited by 24 publications

References 37 publications

Programmable droplet manipulation and wetting with soft magnetic carpets

Programmable droplet manipulation and wetting with soft magnetic carpets

Prediction of Droplet Sliding on the Continuity of the Three-Phase Contact Line

Preparation and Wetting Mechanism of Laser‐Etched Composite Self‐Assembled 1H,1H,2H,2H‐Perfluorodecyltriethoxysilane Superhydrophobic Surface Coating

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