Dynamics of ferrofluid drops on magnetically patterned surfaces

Subscriber access provided by University of South Dakota

Interface Components: Nanoparticles, Colloids, Emulsions, Surfactants, Proteins, Polymers

Dynamics of ferrofluid drops on magnetically patterned surfaces Carlo Rigoni, Davide Ferraro, Matteo Carlassara, Daniele Filippi, Silvia Varagnolo, Matteo Pierno, Delphine Talbot, Ali Abou-Hassan, and GIAMPAOLO MISTURA Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.8b01520 • Publication Date (Web): 03 Jul 2018 Downloaded from http://pubs.acs.org on July 6, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Dynamics of ferrofluid drops on magnetically patterned surfaces C. Rigoni a, D. Ferraro a, M. Carlassara a, D. Filippi a, S. Varagnolo*a, M. Pierno a, D. Talbotb, A. Abou-Hassan b and G. Misturaa

a

Dipartimento di Fisica e Astronomia G.Galilei, Università di Padova, via Marzolo 8, 35131 Padova,

Italy, bSorbonne Université, CNRS, Laboratoire PHysico-chimie des Electrolytes et Nanosystèmes, PHENIX, F-75005 Paris, France.

Corresponding author: [email protected] *present address: Department of Chemistry, University of Warwick, United Kingdom CV4 7AL.

ACS Paragon Plus Environment

1

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 19

Abstract The motion of liquid drops on solid surfaces is attracting a lot of attention because of its fundamental implications and wide technological applications. In this article, we present a comprehensive experimental study of the interaction between gravity driven ferrofluid drops on very slippery oil impregnated surfaces and a patterned magnetic field. The drop speed can be accurately tuned by the magnetic interaction and, more interestingly, drops are found to undergo a stick-slip motion whose contrast and phase can be easily tuned by changing either the strength of the magnetic field or the ferrofluid concentration. This motion is the result of the periodic modulation of the external magnetic field and can be accurately analyzed because the intrinsic pinning due to chemical defects is negligible on oil impregnated surfaces.

Keywords Ferrofluid drops. Liquid impregnated surfaces. Wetting of ferrofluid drops on modulated magnetic fields. Gravity driven sessile drops. Stick-slip motion. Friction of ferrofluid drops.


2

Page 3 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Introduction Controlling and predicting the mobility of drops in contact with a solid surface is a major scientific challenge,1 relevant for fundamental research2 and crucial for an ample variety of applications including self-cleaning coatings,3 microfluidics,4 dropwise condensation5 and fog collection.6 In order for a drop to slide on a tilted surface, it must both advance (on the downhill side) and recede (on the uphill side). This implies that the frontal contact angle must be larger than the advancing contact angle , while the rear contact angle must be smaller than the receding contact angle . The difference ∆ = − , known as contact angle hysteresis, is characteristic of the surface chemistry and topography and is the key macroscopic parameter governing drop dynamics.7,

8

Suitable chemically heterogeneous surfaces

can then be tailored to passively control drop motion. For instance, water drops sliding on alternating stripes of different wettability introduce an anisotropic behavior: drops slide more easily along the alternating stripes than across them9,

10

and periodic variations in the contact angles, possibly

accompanied by fluctuations in the drop velocity, take place along this latter direction.10 More interestingly, if the wettability contrast between adjacent stripes is high, drops undergo a stick-slip motion whose average speed can be an order of magnitude smaller than that measured on a homogeneous surface having the same apparent contact angle.11 In fact, this motion is the result of the periodic deformations of the drop interface when crossing the stripes. Lattice Boltzmann simulations reproduce the stick-slip motion and indicate that the slowdown is the result of the pinning-depinning transition of the contact line, which causes energy dissipation to be localized in time and a large part of the driving energy to be stored in the periodic deformations of the contact line when crossing the stripes.11,

12

More recent numerical studies have analyzed further features of the stick-slip motion of

drops on chemically patterned surfaces.13-16 On the other hand, active control of drop motion can be achieved with different approaches.1 Oscillations of the substrate couple to the drop inertia and thus provide, in principle, a universal actuation method for all types of liquids. For instance, vertical vibrations can make drops climb against ACS Paragon Plus Environment

3

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 19

gravity on an inclined plane17 and merge them together.18 Electric fields generated by arrays of electrodes integrated in the surface and covered with an insulating layer are widely used as a tool to control shape, motion and generation of conductive drops.19,

20

Electric fields combined with

temperature can also tune the wettability of graphene sponges for accurate liquid handling.21 Similarly, magnetic fields are extensively employed in microfluidics22 to handle drops,23-25 carry out continuous flow cell separation,26,

27

perform chemical ferrofluid synthesis28 and study the drop breakup

dynamics.29 They are also used to modify the shape of ferrofluid sessile drops and to drag them along a surface.30-34 If ferrofluid drops move on superhydrophobic surfaces in an external magnetic field, their interaction force with the substrate is measured to be very low35 and is defined by the processes occurring in the vicinity of the triple line only.36 In this article we present the first experimental evidence of the role played by a patterned magnetic field on the dynamics of ferrofluid drops. A continuous evolution from uniform to stick-slip motion is observed, which can be tuned by increasing the ferrofluid concentration and/or the magnetic field. More interestingly, the delay between the depinning of the front and rear contact lines is found to depend on the mean speed of the drop. In order to concentrate only on the intrinsic pinning effects caused by inhomogeneous magnetic fields, a rough surface is impregnated with oil. Since the oil surface is intrinsically smooth and free from chemical and morphological defects typical of solid surfaces, these so called liquid-impregnated surfaces (LIS) are recognized to hardly pin sessile drops.1, 37, 38

Methods Ferrofluid-impregnated surfaces have been studied for active manipulation of water droplets39, 40. In this study, instead, we use ferrofluid drops on conventional, non-magnetic LIS produced following the recipe described in:41 a film of silicone oil is spread on the surface of a coverglass and heated at 300°C for 10 minutes; after cooling down the glass at room temperature, the oil in excess is washed away with acetone. Because of the thermal process, the thin solidified silicone layer (≈200 nm of thickness) presents pores that can be easily impregnated by liquid silicone oils.41 The resulting LIS are 4 ACS Paragon Plus Environment

Page 5 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

characterized by performing static and dynamic tests using drops of distilled water and impregnating the solid matrix with three silicone oils of different viscosity (5 cSt, 100 cSt and 1000 cSt). Regardless of the viscosity, the apparent contact angle of sessile water drops is 107°±2° and the contact angle hysteresis is a few degrees (3.1°±0.5°). Similar values are exhibited by ferrofluid drops at different concentrations (see Section 1 in Supporting Information). Furthermore, the downward velocity of water drops of volume Ω=20 µL measured at different inclination angles α and oil viscosities scales as expected42 (see Section 2 in Supporting Information). Based on these preliminary results, the 100 cSt silicone oil is chosen as lubricant for this work because it allows to easily explore an ample interval of velocities with suitable inclinations. Its viscosity (≈100 times that of the ferrofluids) avoids drainage of the impregnated oil by the moving drops and, at the same time, yields very low roll off angles, well below 5°. The ferrofluid drops are stable aqueous colloidal suspensions of maghemite (γ-Fe2O3) nanoparticles in aqueous acidic solutions at pH ∼2 with NO3‾ counterions synthesized following the Massart process,43 which guarantees stable suspensions over long time intervals. The nanoparticles have a rock like shape with a crystal diameter of about 8.5 nm (more details about their synthesis and characterization can be found in our previous work.34) To explore the influence of the magnetic interaction on the dynamics of ferrofluid drops, eight different concentrations are used. The experimental setup allows acquiring images of a drop on an inclined surface.44 As shown in Fig. 1, it is composed by a permanent magnet that can be tilted at a desired angle α by a motor. A white LED back-light source and a high-speed camera are used for illuminating and acquiring the images, respectively. During a typical experiment, a drop (Ω ≈ 10 − 40 µL) is gently placed on the already tilted surface and its motion is recorded. Every image sequence is then processed off-line by a customized LabVIEW program that provides the time evolution of the frontal and rear positions of the drop contact line.44 Side views show that drops are quasi-hemispherical and surrounded by a small oil meniscus as shown in Fig. 1. This circular meniscus,


5

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 19

pulled from the oil film by the surface tension of water,45 is found to persist in dynamical conditions, which impacts the friction opposing the moving drop.46 The permanent magnet is made of neodymium and has a cylindrical shape (diameter 18 cm, height 3 cm). The ample surface guarantees that a drop moving on its central part experiences a uniform magnetic field whose strength depends only on the vertical distance z from the face of the magnet (see Section 3 in Supporting Information). For this study, the distance of the sliding surface from the permanent magnet is 15 mm and the corresponding value of the uniform magnetic field is 148± 2mT. A comb-shape iron sheet (thickness 2 mm) placed on the permanent magnet modulates the magnetic field along the drop sliding direction (x axis), as reported in Fig. 1. The teeth have width of 0.5 mm and period of 1.7 mm. The drop is deposited on the LIS sample placed on the iron comb. By increasing the distance of the sample from the magnet, the modulation of the magnetic field decreases as shown in Fig. 1. The profile of the patterned magnetic field used in this study is that one corresponding to the distance 0.2 mm. The droplet interaction with the magnetic field can be characterized by the effective gravitational acceleration ∗ = + with the acceleration of gravity and = ∇ the magnetic force per unit volume exerted by the magnet, being the ferrofluid magnetization corresponding to B and ∇ the gradient of the magnetic field. For the uniform magnetic field ∗ ~10 m/s2, while on the patterned magnetic field, ∗ locally can be as high as 1300 m/s2 (for further details on the magnetic field see Section 3 of Supporting Information).


6

Page 7 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Figure 1. a) Experimental set-up: a ferrofluid drop of known volume is deposited on a silicone oil impregnated surface tilted by an angle α placed above a permanent magnet. Its stationary speed is denoted as v. To modulate the magnetic field, an iron comb is placed between the magnet and the impregnated surface. b) Spatial modulation of the magnetic field at different distances from the magnet. c) Ferrofluid drop (volume 20 µL, concentration 0.8 mol/L) going down the surface tilted by 5° and d) enlargement of the oil front meniscus pushed by the drop.

Results The left graph of Fig. 2 shows the time evolution of the drop frontal position of ferrofluid drops deposited on lubricant impregnated surfaces inclined by an angle α=25°, in the presence of either a uniform or a modulated magnetic field. The drops subject to a uniform magnetic field slide at a constant ACS Paragon Plus Environment

7

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 19

speed that decreases with ferrofluid concentration. Since no apparent variation in the drop shape and oil meniscus is observed, we ascribe this loss to magnetoviscous effects.47 Actually, the viscosity of maghemite ferrofluids is found to increase with concentration and the application of a magnetic field further enhances this effect48,49 (see Section 4 of Supplemental Information for more details). On a patterned magnetic field, the speed decreases and a pronounced stick-slip motion appears, similar to what reported for water drops sliding on stripes of alternating wettability.11,

44

Selected snapshots

indicate the position of the contact line (CL) with respect to the underlying comb. Between instants a and b, the rear CL is pinned at the edge of a tooth comb while the frontal CL is slowly moving down; at instant c, the frontal CL gets pinned at the edge of a tooth comb and the rear starts moving till in d it gets pinned at the edge of the following tooth comb and the system recovers the initial configuration translated by one pattern periodic distance. This periodic alternation of pinning and depinning between the frontal and rear CL implies an oscillation in the instantaneous length L of the sliding drop. Additionally, the oscillation ∆L, evaluated as the difference between the maximum and minimum measured L, increases with the ferrofluid concentration, as shown in the right graph of Fig 2. Again, the amplitude of these oscillations can be continuously changed from a “rigid” drop moving at constant speed to an oscillating drop undergoing stick-slip motion by varying either the ferrofluid concentration, as done here, or, more generally, the magnetic strength. This tuning is a significant advantage with respect to the passive control provided by chemically heterogeneous surfaces, whose effects on the drop dynamics can only be modified by varying the nature or shape of the different chemical domains.1


8

Page 9 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Figure 2. Left graph: time evolution of the frontal point of ferrofluid drops at different concentrations (Volume = 20 µL) moving on liquid impregnated surfaces inclined by an angle α=25°, in the presence of either a uniform or a patterned magnetic field. The snapshots show the position of the drop with respect to the underlying magnetic pattern at specified instants. The orange lines indicate the contact angles. Right graph: percentage variation of the drop length ∆L during stickslip as a function of ferrofluid concentration. The inset underlines the drop length oscillation (L) during the motion for three particular concentrations.

We exploit this advantage to systematically characterize the phase shift φ of the stick-slip motion by varying both the drop volume and ferrofluid concentration. The phase shift is calculated from the ratio = 360°

∆

, where ∆ is the time interval between the consecutive instants of maximum acceleration of

the frontal and rear contact points, and T is the time interval between two consecutive instants of maximum acceleration of the frontal contact point. Therefore, of the drop, while when

= 0° corresponds to a rigid translation

= 180° the front and rear contact points move in counter-phase. The graph of

Fig. 3 shows the dependence of φ on the drop speed v. A clear linear trend is seen up to v=60 mm/s. The largest drops (Ω=40 µL) reach

= 360° at around 80 mm/s. Above this speed,

keeps on increasing

linearly. Furthermore, two distinct regimes are observed during drop motion. At low speed (shaded area of the graph), only the contours near the front and rear contact lines change during a stick-slip motion as shown by the images (aj) taken at the instant of maximum (minimum) elongation of the moving drop (see also Movie S1 in Supporting Information). At higher speed, the entire drop profile oscillates as indicated by the images b and Movie S2 in Supporting Information. As the speed is further increased, this oscillation becomes more pronounced (see images ci,j and Movie S3 in Supporting Information). If ACS Paragon Plus Environment

9

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 19

we analyze in more detail the data at high ferrofluid concentration where the stick-slip motion is more marked, we find that

does not depend on the ferrofluid concentration and thus the magnetic force.

Figure 3. Left: sliding phase as a function of the drop speed, varying the ferrofluid concentration (different colors), drop volumes (◑=10 µL, ●=20 µL, ◒=30 µL, ○=40 µL). The colored gray background represents conventional stick-slip, while the white part indicates where the vertical oscillations of the drop profile appear. Right: frames at the maximum (i) and minimum (j) elongation instants of drops (40 µL, 0.8 mol/L) moving at three different speeds. The two points b in the graph display the same motion described in the snapshots bi and bj.

To shed more light on the interplay between drop dynamics and magnetic field, systematic measurements are performed at a constant drop volume (Ω=20 µL) by varying the ferrofluid concentration and the angle α. For each combination, the mean drop speed is determined by the slope of least square linear fits of the time evolution of the frontal points, for either uniform (vu) or patterned (vp) magnetic fields. The left graph of Fig. 4 summarizes all speed data plotted in terms of the ferrofluid concentration for increasing inclination angles. It clearly shows that the drop speed decreases with the ferrofluid concentration as already discussed. At high concentrations (> 0.4 mol/L), the presence of the comb significantly slows down the drops as compared with the uniform field, indicating the presence of an extra dissipation due to deformation of the drop undergoing stick-slip. This decrease is larger at higher concentrations where the stick-slip motion is more pronounced, as displayed in the inset of Fig. 4, where the relative velocity decrease ∆" =

#$ %#& #$

is plotted as a function of α. The comb reduces the

drop speed by about 35% for a ferrofluid concentration of 0.8 mol/L, and it is barely observable at the ACS Paragon Plus Environment

10

Page 11 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

concentration 0.1 mol/L. Interestingly, this decrease does not seem to depend on the inclination angle, at least in the explored range. Finally, as a result of the weak pinning LIS, we notice that this decrease is much smaller than the factor of ten reported for water drops sliding on chemically heterogeneous surfaces.11, 44 The right graph of Fig. 4 displays the velocity in a log scale as a function of the sine of the tilt angle for ferrofluid drops having Ω = 20 mL and different molar concentrations, in the presence of either uniform or patterned magnetic fields. On this compressed scale, the differences in drop velocity observed between the uniform and patterned magnetic fields disappear and the data show that v is not linear in driving force but rather exhibits a power law behavior. For this system where the silicone oil is more viscous than the ferrofluid, dissipation is expected to mainly occur in the oil, that is, in the underlying film and in the surrounding meniscus. A recent study46 shows that, contrary to what one could think a priori, the dominant contribution is not in the subjacent film. The analysis of the viscous effects in the front edge of the moving meniscus yields nonlinear friction and estimates that "~'()*⁄+ -.46 As the driving force is increased, the wedge dissipation is suddenly suppressed, which leads to a different dynamical regime that seems to arise from the self-lubrication of the drop where "~'()* -, explained assuming that oil is constantly extracted from the texture by water surface tension before being reinjected below the drop.46 Our results indicate a superlinear behavior which, at the highest inclinations and in the presence of a uniform magnetic field (full symbols), is consistent with a power law with exponent 3. As sin - decreases, the exponent becomes smaller and there may be a cross-over to the '()*⁄+ - regime at a critical velocity "~1 cm/s. Finally, as expected, the data on the patterned surface show a distinct behavior, a clear indication that the modulation of the magnetic field contributes to friction.


11

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 19

Figure 4. Left graph: mean velocity of ferrofluid drops (Ω=20 µL) of different concentrations moving on LIS at increasing inclination angles in the presence either of a uniform (U, open symbols) or a patterned (P, full symbols) magnetic field. The inset compares the relative velocity decrease at two ferrofluid concentrations (the points enclosed in the two dashed boxes) on the same patterned surface at increasing -. Right graph: the same data plotted in terms of sin - proportional to the in plane component of the gravitational driving force.

In summary, we have characterized, for the first time, the influence of a magnetic field on the motion of ferrofluid drops on very slippery surfaces. The application of a uniform magnetic field slows down gravity driven ferrofluid drops. The presence of magnetic heterogeneities significantly enriches the drop dynamics. In particular, a linear modulation in the magnetic field causes stick-slip whose contrast and phase can be easily tuned. In particular, the phase shift between the moving frontal and rear contact points change continuously with the drop velocity from 0 to 2π. These observations are possible because the intrinsic pinning due to chemical defects is negligible on oil impregnated surfaces. More precisely, these effects could be seen also with a standard solid surface, but the data reproducibility would be much lower and to construct a graph of the phase variation like that of figure 3 would be practically impossible. A specific feature of LIS is the nonlinear friction of moving drops, which we have measured and found to be consistent with a recent specific study46 where it is attributed to the dissipation taking place in the oil meniscus surrounding the drop. These experimental results suggest that ferrofluid drops moving in the presence of heterogeneous magnetic fields represent an ideal playground for fundamental studies on drop dynamics and provide useful strategies for passive and active control of the drop ACS Paragon Plus Environment

12

Page 13 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

motion. Surprisingly, there is very little in the literature on the dynamics of ferrofluid drops in the presence of magnetic fields. It is our hope that this preliminary work be a stimulus for further studies, both experimental and theoretical.

SUPPORTING INFORMATION Wetting characterization of ferrofluid drops. Motion of water droplets on LIS. Characterization of the permanent magnet. Magnetorheology of the ferrofluid solution. Three movies showing the motion of ferrofluid drops on patterned magnetic fields.

ACKNOWLEDGEMENTS We thank Prof. Régine Perzynski from PHENIX laboratory, Sorbonne Université and Prof. Jean-Claude Bacri from MSC laboratory, Paris 7 for discussions and Giorgio Delfitto for assistance in the assembly of the experimental set-up.


13

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 19

REFERENCES 1.

Mistura, G.; Pierno, M., Drop mobility on chemically heterogeneous and lubricant-impregnated

surfaces. Advances in Physics: X 2017, 2, 591-607. 2.

Bonn, D.; Eggers, J.; Indekeu, J.; Meunier, J.; Rolley, E., Wetting and spreading. Reviews of

Modern Physics 2009, 81, 739-805. 3.

Quere, D., Wetting and roughness. Annual Review of Materials Research 2008, 38, 71-99.

4.

Seemann, R.; Brinkmann, M.; Pfohl, T.; Herminghaus, S., Droplet based microfluidics. Reports

on Progress in Physics 2012, 75, 016601. 5.

Park, K. C.; Kim, P.; Grinthal, A.; He, N.; Fox, D.; Weaver, J. C.; Aizenberg, J., Condensation

on slippery asymmetric bumps. Nature 2016, 531, 78-82. 6.

Malik, F. T.; Clement, R. M.; Gethin, D. T.; Krawszik, W.; Parker, A. R., Nature's moisture

harvesters: a comparative review. Bioinspiration & Biomimetics 2014, 9 031002. 7.

Extrand, C. W., Contact angles and hysteresis on surfaces with chemically heterogeneous

islands. Langmuir 2003, 19, 3793-3796. 8.

Gao, L. C.; McCarthy, T. J., Contact angle hysteresis explained. Langmuir 2006, 22, 6234-6237.

9.

Morita, M.; Koga, T.; Otsuka, H.; Takahara, A., Macroscopic-wetting anisotropy on the line-

patterned surface of fluoroalkylsilane monolayers. Langmuir 2005, 21, 911-918. 10.

Suzuki, S.; Nakajima, A.; Tanaka, K.; Sakai, M.; Hashimoto, A.; Yoshida, N.; Kameshima, Y.;

Okada, K., Sliding behavior of water droplets on line-patterned hydrophobic surfaces. Applied Surface Science 2008, 254, 1797-1805. 11.

Varagnolo, S.; Ferraro, D.; Fantinel, P.; Pierno, M.; Mistura, G.; Amati, G.; Biferale, L.;

Sbragaglia, M., Stick-Slip Sliding of Water Drops on Chemically Heterogeneous Surfaces. Physical Review Letters 2013, 111, 066101.


14

Page 15 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

12.

Langmuir

Sbragaglia, M.; Biferale, L.; Amati, G.; Varagnolo, S.; Ferraro, D.; Mistura, G.; Pierno, M.,

Sliding drops across alternating hydrophobic and hydrophilic stripes. Physical Review E 2014, 89, 012406. 13.

Li, Q.; Zhou, P.; Yan, H. J., Pinning-Depinning Mechanism of the Contact Line during

Evaporation on Chemically Patterned Surfaces: A Lattice Boltzmann Study. Langmuir 2016, 32, 93899396. 14.

Zhao, J. Y.; Chen, S.; Liu, Y., Droplets motion on chemically/topographically heterogeneous

surfaces. Molecular Simulation 2016, 42, 1452-1459. 15.

Liu, M.; Chen, X. P., Numerical study on the stick-slip motion of contact line moving on

heterogeneous surfaces. Physics of Fluids 2017, 29, 082102. 16.

Zhao, J. Y.; Chen, S.; Liu, Y., Dynamical behaviors of droplet impingement and spreading on

chemically heterogeneous surfaces. Applied Surface Science 2017, 400, 515-523. 17.

Brunet, P.; Eggers, J.; Deegan, R. D., Vibration-induced climbing of drops. Physical Review

Letters 2007, 99 , 144501. 18.

Sartori, P.; Quagliati, D.; Varagnolo, S.; Pierno, M.; Mistura, G.; Magaletti, F.; Casciola, C. M.,

Drop motion induced by vertical vibrations. New Journal of Physics 2015, 17, 113017. 19.

Mugele, F.; Baret, J. C., Electrowetting: From basics to applications. Journal of Physics-

Condensed Matter 2005, 17, 705-774. 20.

Choi, K.; Ng, A. H. C.; Fobel, R.; Wheeler, A. R., Digital Microfluidics. In Annual Review of

Analytical Chemistry, Vol 5, Cooks, R. G.; Yeung, E. S., Eds. Annual Reviews: Palo Alto, 2012; Vol. 5, pp 413-440. 21.

Wang, J.; Sun, L. Y.; Zou, M. H.; Gao, W.; Liu, C. H.; Shang, L. R.; Gu, Z. Z.; Zhao, Y. J.,

Bioinspired shape-memory graphene film with tunable wettability. Science Advances 2017, 3, e1700004. 22.

Zhang, Y.; Nguyen, N. T., Magnetic digital microfluidics - a review. Lab on a Chip 2017, 17,

994-1008. ACS Paragon Plus Environment

15

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

23.

Page 16 of 19

Nam-Trung, N., Micro-magnetofluidics: interactions between magnetism and fluid flow on the

microscale. Microfluidics and Nanofluidics 2012, 12, 1-16. 24.

Teste, B.; Jamond, N.; Ferraro, D.; Viovy, J. L.; Malaquin, L., Selective handling of droplets in a

microfluidic device using magnetic rails. Microfluidics and Nanofluidics 2015, 19, 141-153. 25.

Ferraro, D.; Champ, J.; Teste, B.; Serra, M.; Malaquin, L.; Viovy, J. L.; de Cremoux, P.;

Descroix, S., Microfluidic platform combining droplets and magnetic tweezers: application to HER2 expression in cancer diagnosis. Scientific Reports 2016, 6, 25540. 26.

Saliba, A. E.; Saias, L.; Psychari, E.; Minc, N.; Simon, D.; Bidard, F. C.; Mathiot, C.; Pierga, J.

Y.; Fraisier, V.; Salamero, J.; Saada, V.; Farace, F.; Vielh, P.; Malaquin, L.; Viovy, J. L., Microfluidic sorting and multimodal typing of cancer cells in self-assembled magnetic arrays. Proceedings of the National Academy of Sciences of the United States of America 2010, 107, 14524-14529. 27.

Hejazian, M.; Li, W. H.; Nguyen, N. T., Lab on a chip for continuous-flow magnetic cell

separation. Lab on a Chip 2015, 15, 959-970. 28.

Ferraro, D.; Lin, Y.; Teste, B.; Talbot, D.; Malaquin, L.; Descroix, S.; Abou-Hassan, A.,

Continuous chemical operations and modifications on magnetic gamma-Fe2O3 nanoparticles confined in nanoliter droplets for the assembly of fluorescent and magnetic SiO2@gamma-Fe2O3. Chemical Communications 2015, 51, 16904-16907. 29.

Wu, Y. N.; Fu, T. T.; Ma, Y. G.; Li, H. Z., Ferrofluid droplet formation and breakup dynamics in

a microfluidic flow-focusing device. Soft Matter 2013, 9, 9792-9798. 30.

Latikka, M.; Backholm, M.; Timonen, J. V. I.; Ras, R. H. A., Wetting of ferrofluids: Phenomena

and control. Current Opinion in Colloid & Interface Science 2018, DOI: 10.1016/j.cocis.2018.04.003. 31.

Asakura, H.; Nakajima, A.; Munetoshi, S.; Suzukia, S.; Kameshima, Y.; Okada, K., Deformation

and motion by gravity and magnetic field of a droplet of water-based magnetic fluid on a hydrophobic surface. 2007, 253, 3098–3102.


16

Page 17 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

32.

Langmuir

Nguyen, N.-T.; Zhu, G.; Chua, Y.-C.; Phan, V.-N.; Tan, S.-H., Magnetowetting and Sliding

Motion of a Sessile Ferrofluid Droplet in the Presence of a Permanent Magnet. Langmuir 2010, 26, 12553-12559. 33.

Nam-Trung, N., Deformation of Ferrofluid Marbles in the Presence of a Permanent Magnet.

Langmuir 2013, 29, 13982-13989. 34.

Rigoni, C.; Pierno, M.; Mistura, G.; Talbot, D.; Massart, R.; Bacri, J. C.; Abou-Hassan, A.,

Static Magnetowetting of Ferrofluid Drops. Langmuir 2016, 32, 7639-7646. 35.

Guo, Z.-G.; Zhou, F.; Hao, J.-C.; Liang, Y.-M.; Liu, W.-M.; Huck, W. T. S., “Stick and slide”

ferrofluidic droplets on superhydrophobic surfaces. Applied Physics Letters 2006, 89, 081911. 36.

Bormashenko, E.; Pogreb, R.; Bormashenko, Y.; Musin, A.; Stein, T., New Investigations on

Ferrofluidics: Ferrofluidic Marbles and Magnetic-Field-Driven Drops on Superhydrophobic Surfaces. Langmuir 2008, 24, 12119 - 1212. 37.

Lafuma, A.; Quere, D., Slippery pre-suffused surfaces. European Physics Letters 2011, 96,

56001. 38.

Wong, T.-S.; Kang, S. H.; Tang, S. K. Y.; Smythe, E. J.; Hatton, B. D.; Grinthal, A.; Aizenberg,

J., Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity. Nature 2011, 477, 443-447. 39.

Khalil, K. S.; Mahmoudi, S. R.; Abu-dheir, N.; Varanasi, K. K., Active surfaces: Ferrofluid-

impregnated surfaces for active manipulation of droplets. Applied Physics Letters 2014, 105, 041604. 40.

Irajizad, P.; Ray, S.; Farokhnia, N.; Hasnain, M.; Baldelli, S.; Ghasemi, H., Remote Droplet

Manipulation on Self-Healing Thermally Activated Magnetic Slippery Surfaces. Advanced Materials Interfaces 2017, 4, 1700009. 41.

Eifert, A.; Paulssen, D.; Varanakkottu, S. N.; Baier, T.; Hardt, S., Simple Fabrication of Robust

Water-Repellent Surfaces with Low Contact-Angle Hysteresis Based on Impregnation. Advanced Materials Interfaces 2014, 1, 1300138.


17

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

42.

Page 18 of 19

Smith, J. D.; Dhiman, R.; Anand, S.; Reza-Garduno, E.; Cohen, R. E.; McKinley, G. H.;

Varanasi, K. K., Droplet mobility on lubricant-impregnated surfaces. Soft Matter 2013, 9, 1772-1780. 43.

Massart, R., Preparation of aqueous magnetic liquids in alkaline and acidic media. IEEE

Transactions on Magnetics 1981, 17, 1247-1248. 44.

Varagnolo, S.; Schiocchet, V.; Ferraro, D.; Pierno, M.; Mistura, G.; Sbragaglia, M.; Gupta, A.;

Amati, G., Tuning Drop Motion by Chemical Patterning of Surfaces. Langmuir 2014, 30, 2401-2409. 45.

Schellenberger, F.; Xie, J.; Encinas, N.; Hardy, A.; Klapper, M.; Papadopoulos, P.; Butt, H. J.;

Vollmer, D., Direct observation of drops on slippery lubricant-infused surfaces. Soft Matter 2015, 11, 7617-7626. 46.

Keiser, A.; Keiser, L.; Clanet, C.; Quere, D., Drop friction on liquid-infused materials. Soft

Matter 2017, 13, 6981-6987. 47.

Odenbach, S., FerrofluidsMagnetically Controllable Fluids and Their Applications. Springer:

2002. 48.

Ghasemi, E.; Mirhabibi, A.; Edrissi, M., Magnetoviscous Effect in a Maghemite Ferrofluid.

Journal of Nanoscience and Nanotechnology 2011, 11, 5285-5291. 49.

Galindo-Gonzalez, C.; Ponton, A.; Bee, A.; Chevalet, J.; Talbot, D.; Perzynski, R.; Dubois, E.,

Investigation of water-based and oil-based ferrofluids with a new magnetorheological cell: effect of the microstructure. Rheologica Acta 2016, 55, 67-81.


18

Page 19 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

TABLE OF CONTENT


19

Dynamics of ferrofluid drops on magnetically patterned surfaces

Recommend Documents