"'Armored"' Bubbles and Droplets
Colloidal particles absorbed on liquid interfaces have long been reported to stabilize emulsions and foams. Recently, individual droplets densely covered with small particles have been proposed as a possible means of obtaining a variety of composite particles and hollow locked shells. Such interfacially structured and protected materials offer new opportunities in many fields as diverse as optics, encapsulation, biomedicine, non-wetting droplets, stabilizing gas bubbles, mineral flotation, drug delivery and foods. Particles shells produced with current methods vary widely in size, quality and stability, and have only been produced in batch sizes. Furthermore, additional chemical or thermal locking steps have to be performed to increase the stability and adjust the mechanical properties of the shells.
The invention presents a method for directing hydrodynamic energy to a number of particles to cause them to form a shell around a fluidic droplet ("colloidal armor") where the fluidic droplet can be either liquid or gaseous. The method uses flow focusing and the device as described in Harvard Case 2215 (http://www.techtransfer.harvard.edu/cgi-bin/TALSearch.cgi?full_report=1AMPERSANDcase=2215). The particles are stabilized through jamming on the surface creating a completely protected and stable fluidic droplet. The colloidal armor is not limited by the properties of the fluid core it protects nor is it, in contrast to competing technologies, necessary to modify the surface by chemical or thermal sintering steps. Intrinsic mechanical properties of the armored droplets, which can be tuned, also allow the production of topographically complex, compartmentalized or multi-armored droplets. Finally, colloidal armor can be controllably disassembled by the addition of surfactants, thus allowing controlled release of contents.
* The technology could be used as a simple reversible method for transporting and releasing Brownian masse (particles on the surface).
* Utilize magnetic particles in the armored shell in order to specifically target cancer cells with encapsulated fluids.
* Stabilize fluid droplets in liquid. The technology could potentially offer a better way of stabilizing contrast agents for diagnostic ultrasound imaging.
* Shaping of fluidic droplets into various anisotropic shapes. Could possibly be used to create a variety of optical affects in personal hygiene products.
* A more efficient way to encapsulate fluids and chemical substances especially related to food and drugs.
* Does not require additional chemical or thermal excitement in order to form particle shells which reduce the time and number of steps in the process.
* Indications have been found that the fluidic bubbles would be stable for a very long time compared to other encapsulation technologies. Possibly applicable in efforts to extend due dates of food etc.
* It has previously not been possible to form complex non-spherical shapes of fluidic droplets.
* Offers a more efficient way to transport brownian particles.
Intellectual Property Status: A patent application has been filed by Harvard University and is pending.
Publications: A. Bala Subramaniam, M. Abkarian and H.A. Stone 2005 Controlled Assembly of Jammed Colloidal Shells on Fluid Droplets. Nature Matls. 4, 553-556.
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Stone, Howard A
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