Synthesis of Temperature-Sensitive Magnetic Microcapsules and Visualization of Cluster Formation

Temperature-sensitive magnetic fluids flow spontaneously in a magnetic field when there is a temperature difference and thus may be used in cooling devices operated without external power. However, magnetic fluids are difficult to mass-produce, and the dispersion ability of the working fluid cannot be controlled. We use magnetic material encapsulated in microcapsules of large diameter to function as a new type of refrigerant. By enclosing the magnetic material in capsules, they can be used with any working fluid. We made solid particles containing kerosene-based magnetic fluid in polymer. When a magnetic field was applied, the particles aggregated and formed clusters. A scanning electron microscope and focused ion beam system were used to determine the particle shapes. Particles 5-50 μm in size could be created by varying the rotation speed of the homogenizer during the synthesis.