Microparticles and apparatus for smart ink production

1. A microparticle comprising: a) an exterior shell; b) a liquid encapsulated within the shell; and c) a Janus microparticle suspended in the liquid, wherein the Janus microparticle either comprises:

a. two or more distinct assemblies of particles; or

b. a core loaded with particles, the core having a first surface portion and a second surface portion that is functionally distinct from the first surface portion.

2. The microparticle of claim 1 , wherein the Janus particle comprises two distinct assemblies of particles; each assembly of particles is embedded in a polymer; and the particles are selected from the group consisting of dyes, pigments, functional nanoparticles and any combination thereof.

3. The microparticle of claim 2 , wherein a first assembly comprises a polymerized first monomer loaded with fluorescent silica nanoparticles and a second assembly comprises a polymerized second monomer loaded with plasmonic magnetic nanoparticles, the second monomer miscible or immiscible with the first monomer.

4. The microparticle of claim 2 , wherein the plasmonic magnetic nanoparticles are gold-silica coated iron oxide nanoparticles.

5. The microparticle of claim 1 , wherein the Janus particle comprises a core, the core is either a homogenous polymer or inorganic, and the core is loaded with particles selected from the group consisting of dyes, pigments, functional nanoparticles and any combination thereof.

6. The microparticle of claim 5 , wherein at least one of the first and second surface portions are coated with either: a) a thin film; or b) a monolayer of nanoparticles that is subsequently covered with a thin optical film.

7. The microparticle of claim 6 , wherein the thin film or the nanoparticles are magnetic.

8. The microparticle of claim 1 comprising an exterior polymeric or inorganic shell.

9. The microparticle of claim 6 , wherein the exterior shell comprises silica.

10. The microparticle of claim 1 , wherein the liquid is selected from an aqueous solution, oil, lubricant, ionic liquid and a resin.

11. The microparticle of claim 1 , wherein the liquid has volatility of less than 23 torr at room temperature.

12. The microparticle of claim 1 , wherein the Janus particle orients in response to an applied external field.

13. A microfluidic device for fabrication of the microparticle of claim 1 comprising: a first microfluidic channel that simultaneously intersects a second and third microfluidic channel at a first flow-focus junction leading to a fourth microfluidic channel; and the fourth microfluidic channel simultaneously intersects a fifth and sixth microfluidic channel at a second flow-focus junction leading to a seventh microfluidic channel, wherein the first flow-focus junction has a height and width that is less than a height and width of the fourth microfluidic channel.

14. The microfluidic device of claim 13 , wherein the second flow-focus junction has a height and width that is less than a height and width of the seventh microfluidic channel.

15. The microfluidic device of claim 13 , wherein each flow-focus junction has an aspect ratio of between 0.5 and 2.

16. The microfluidic device of claim 13 , further comprising a UV source applied after the seventh microfluidic channel.

17. The microfluidic device of claim 13 , wherein a dispersion of the Janus microparticle in the liquid flows in the first microfluidic channel; a continuous phase of a monomer flows in the second and third microfluidic channels; a double emulsion of droplets flows in the fourth microfluidic channel; a second liquid immiscible with the liquid flows in the fifth and sixth microfluidic channels; and a triple emulsion flows in the seventh microfluidic channel, wherein the double emulsion comprises droplets of the Janus microparticle in the liquid surrounded by the continuous phase of the monomer; and the triple emulsion comprises the Janus particle immersed in the liquid encapsulated by the monomer surround by a continuous phase of the second liquid.

18. The microfluidic device of claim 13 , further comprising a prejunction prior to the first microfluidic channel, the prejunction consisting of the intersection of a plurality of additional microfluidic channels.

19. A plurality of the microparticles of claim 1 dispersed in an ink composition.

20. A method of fabricating the microparticle of claim 1 using a flow focusing microfluidic system, comprising the steps of:

i) dispersing the Janus microparticle into the liquid in a first microfluidic channel of the microfluidic system to form a dispersion;

ii) injecting the dispersion into a first junction intercepted by two monomer microfluidic channels, each monomer microfluidic channel carrying a continuous phase of a monomer towards the first junction, thereby forming a double emulsion composed of droplets surrounded by the continuous phase of the monomer, each droplet consisting of the Janus microparticle encapsulated by the liquid;

iii) flowing the double emulsion through a second junction intercepted by two liquid microfluidic channels, each liquid microfluidic channel carrying a continuous phase of a second liquid, the second liquid immiscible with the liquid, thereby forming a triple emulsion composed of the Janus particle immersed in the liquid encapsulated by the monomer surround by a continuous phase of the second liquid; and

iv) applying a UV source to the triple emulsion thereby polymerizing the monomer to form the external shell.