Fig 1.
(a) The diameter distribution of magnetic nanoparticles and (b) the magnetization curve of the ferrofluid.
Fig 2.
The proposed system for the formation of water droplets under gravity.
Fig 3.
Variations of (a) non-dimensional diameter and (b) the frequency of droplet generation in terms of the tilting angle for different water flow rates.
The vertex angle is 90°. (c) non-dimensional diameter and frequency of droplet generation against the tilting angle at vertex angles of 30° and 90° at a constant flow rate of 2 ml h-1.
Fig 4.
Schematic of the experimental setup for the generation of ferrofluid droplets using a magnet.
Table 1.
Comparison of measured contact angle of ferrofluid droplets on hydrophilic and hydrophobic surfaces.
Fig 5.
Magnetic flux density in the x and z directions against the distance from the magnet.
Fig 6.
Ferrofluid droplet generation on a functional wedged surface atθ = 20°, Q = 5 ml h-1 and L = 10 mm. τ = tbreakup -t represents the remaining time until the droplet formation.
Fig 7.
(a) Dimensionless diameter and (b) droplet generation frequency versus the magnet distance from the vertex of the hydrophilic surface for different ferrofluid injection rates and the triangle vertex angle of 10°.
Each measurement is an average of at least five droplets. The standard deviation is significantly small and is not visible.
Fig 8.
(a) Convex, triangular, and concave geometry at a constant vertex angle.
(b) Comparison of the effect of the hydrophilic part geometry, including convex, triangle, and concave, on the diameter of the droplet formed at different vertex angles for constant values of Q = 10 ml h-1 and L = 10 mm, (c) Comparison of the effect of the symmetric and asymmetric triangles on the diameter of the droplet formed at different vertex angles for constant values of Q = 10 ml h-1 and L = 10 mm. (d) Variations of dimensionless diameter and droplet generation frequency for trapezoidal geometry with top sides of 1.5, 2.3, and 3.5 mm and its comparison with a triangle with a vertex angle of 10° for constant values of Q = 10 ml h-1 and L = 10 mm.
Fig 9.
Free diagram of forces exerted on the control mass .
Fig 10.
Non-dimensional diameter of droplets versus magnetic and gravitational Bond Number.
For these regressions, Pearson’s correlation coefficient (R2) is greater than 0.95.
Table 2.
Values of geometry function for some typical hydrophilic surface geometries.
Fig 11.
(a) The proposed system for the parallel generation of ferrofluid droplets is inspired by cactus geometry.
It involves the formation of two droplets in the right geometry and four droplets in the left geometry. (b) The proposed system for parallel ferrofluid droplet generation uses a star geometry for the hydrophilic part and an annular magnet. (c) The parallel formation of three to six droplets uses stars with three to six vertices. (d) visual comparison of the 3 (first row) and 4 (second row)-vertices star shaped patterns. Red arrows show the instances of droplet pinching off. Time interval between frames showed is 30 ms.