Department of Electrical Engineering and Automation

Ferrofluidic manipulator for particles and droplets

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Ferrofluidic manipulator
Ferrofluid manipulator: manipulating small-scale non-magnetic objects at the air-ferrofluid interface.

Magnetic manipulation is a widely used method for manipulating small objects that are magnetic. However, most objects in nature and our lives are not magnetic. 

Ferrofluids are liquids containing magnetic nanoparticles that deform under the influence of magnetic fields. By precisely controlling the magnetic fields, we can control the surface of ferrofluid making it a soft hand that can manipulate a wide range of objects that are not magnetic, both solid and liquid.

In this research, we discovered new motion mechanisms for trapping nonmagnetic particles besides pushing them. We have also developed a ferrofluidic manipulator that can manipulate nonmagnetic particles on the air-liquid interface. The ferrofluid manipulator is versatile with the materials and the shapes of the objects under manipulation. We have successfully manipulated particles made of polyethylene, polystyrene, a silicon chip, and poppy and sesame seeds.

Automatic path-following manipulation of a polyethylene (PE) and a polystyrene (PS) particle, a silicon (Si) chip; a poppy seed and sesame in writing the letters “AALTO.” Trajectory (in yellow) is down sampled three times. Scale bar is 2 mm.
Automatic path-following manipulation of a polyethylene (PE) and a polystyrene (PS) particle, a silicon (Si) chip; a poppy seed and sesame in writing the letters “AALTO.” Trajectory (in yellow) is down sampled three times. Scale bar is 2 mm.
Ferrofludic manipulator shaping a hexadecane droplet
Ferrofluidic manipulator shaping a hexadecane droplet (scale bar 2 mm)

We can also use the ferrofluidic manipulator to squeeze, rotate, and shape nonmagnetic liquids on an air−ferrofluid interface with programmable deformation. We can control the aspect ratio of the ellipse and generate repeatable quasi-static shapes of a hexadecane oil droplet. We can rotate droplets and stir liquids into spiral-like structures. We can also shape phase-changing liquids and fabricate shape-programmed thin films at the air−ferrofluid interface. 

Selected publications:

  1. Cenev, Zoran; Harischandra, P. A. Diluka; Nurmi, Seppo; Latikka, Mika; Hyninen, Ville; Ras, Robin A.; Timonen, Jaakko V.I.; Zhou, Quan, "Ferrofluidic Manipulator Automatic Manipulation of Non-magnetic Microparticles at Air-Ferrofluid Interface", IEEE/ASME Transactions on Mechatronics, 26(4), pp. 1932-1940, 2021. 
  2. Cenev, Z., Würger, A. and Zhou, Q., “Motion and Trapping of Micro-and Millimeter Spheroid Particles on the Air-Paramagnetic Liquid Interface”, Physical Review E, 103, L010601, 2021.
  3. Cenev, Z.M., Havu, V., Timonen, J.V. and Zhou, Q., "Ferrofluidic Manipulator: Theoretical Model for Single-Particle Velocity", IEEE/ASME Transactions on Mechatronics, 28(5), pp. 2679-2689, 2023.
  4. Harischandra, P.D., Välisalmi, T., Cenev, Z.M., Linder, M.B. and Zhou, Q., "Shaping Liquid Droplets on an Active Air–Ferrofluid Interface", Langmuir, 39(22), pp. 7623–7631, 2023.
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