Method of forming microsphere having structural color

1. A method of forming a microsphere having a structural color, the method comprising:

providing a composition for generating a structural color, the composition including a curable material and magnetic nanoparticles dispersed in the curable material;

adding the composition for generating a structural color to an immiscible solvent to form an emulsion including spherical droplets of the curable material dispersed in the immiscible solvent, each spherical droplet including the magnetic nanoparticles dispersed therein;

applying a magnetic field to the emulsion to align the magnetic nanoparticles located in each spherical droplet of the curable material in one-dimensional chain structures; and

curing the spherical droplets dispersed in the immiscible solvent while applying the magnetic field to the emulsion to i) fix the chain structures formed by the aligned magnetic nanoparticles in each spherical droplet and ii) form the microsphere which is cured and dispersed in the immiscible solvent, the microsphere including the fixed chain structures which are formed by the magnetic nanoparticles aligned and fixed in the cured material and having the structural color generated by a diffraction of light passing through the microsphere,

wherein the microsphere contains an ordered structure of a photonic crystal due to the alignment of the magnetic nanoparticles, and a diffraction angle of the light passing through the microsphere is changed with rotation of the microsphere.

2. The method according to claim 1 , wherein the magnetic nanoparticles include a superparamagnetic material.

3. The method according to claim 1 , wherein the magnetic nanoparticles have a structure coated with a shell layer surrounding a core formed in a cluster of magnetic nanocrystals.

4. The method according to claim 3 , further comprising a solvation layer coating a surface of the magnetic nanoparticles.

5. The method according to claim 1 , further comprising changing the structural color from a first color into a second color by changing a diffraction angle of the light passing through the microsphere by rotating the microsphere.

6. The method according to claim 5 , wherein a magnetic field strength required to rotate the microsphere is dependent on an amount of the magnetic particles in the microsphere.

7. The method according to claim 1 , further comprising dispersing a plurality of microspheres each having the structural color in a phase-changeable matrix.

8. The method according to claim 7 , wherein when the phase-changeable matrix is in a liquid phase, adjusting an angle of the external magnetic field to change an orientation of the plurality of microspheres.

9. The method according to claim 8 , wherein when the phase-changeable matrix is changed into a solid phase, the orientation of the plurality of microspheres is fixed.

10. The method according to claim 1 , wherein the microsphere has an average diameter of approximately 1 to 300 μm.

11. A method of forming a microsphere having a structural color, the method comprising:

providing a composition for generating a structural color, the composition including a curable material and magnetic nanoparticles dispersed in the curable material;

adding the composition for generating a structural color to an immiscible solvent to form an emulsion including spherical droplets of the curable material dispersed in the immiscible solvent, each spherical droplet including the magnetic nanoparticles dispersed therein;

applying a magnetic field to the emulsion to align the magnetic nanoparticles located in each spherical droplet of the curable material in one-dimensional chain structures; and

curing the spherical droplets dispersed in the immiscible solvent while applying the magnetic field to the emulsion to i) fix the chain structures formed by the aligned magnetic nanoparticles in each spherical droplet and ii) form the microsphere which is cured and dispersed in the immiscible solvent, the microsphere including the fixed chain structures which are formed by the magnetic nanoparticles aligned and fixed in the cured material and having the structural color generated by a diffraction of light passing through the microsphere,

wherein the curable material is a monomer or oligomer containing a crosslinkable site.

12. A method of forming a microsphere having a structural color, the method comprising:

providing a composition for generating a structural color, the composition including a curable material and magnetic nanoparticles dispersed in the curable material;

adding the composition for generating a structural color to an immiscible solvent to form an emulsion including spherical droplets of the curable material dispersed in the immiscible solvent, each spherical droplet including the magnetic nanoparticles dispersed therein;

applying a magnetic field to the emulsion to align the magnetic nanoparticles located in each spherical droplet of the curable material in one-dimensional chain structures; and

curing the spherical droplets dispersed in the immiscible solvent while applying the magnetic field to the emulsion to i) fix the chain structures formed by the aligned magnetic nanoparticles in each spherical droplet and ii) form the microsphere which is cured and dispersed in the immiscible solvent, the microsphere including the fixed chain structures which are formed by the magnetic nanoparticles aligned and fixed in the cured material and having the structural color generated by a diffraction of light passing through the microsphere,

wherein the structural color is a function of an external magnetic field, a size of the magnetic nanoparticles and a shell thickness of the nanoparticles.