Double Emulsion Droplets as Microreactors for Synthesis of Mesoporous Hydroxyapatite

We introduce a novel approach for synthesizing mesoporous hydroxyapatite (HAp, (Ca)(10), (PO4)(6)(OH)(2)) using double emulsion droplets as microreactors. By using capillary microfluidic techniques, the size and the geometry of the droplet microreactors can be tuned easily. Double emulsion droplets offer the combined advantages of both shielding the reactants and on-demand addition of reactants; this makes them highly versatile microreactors. Such droplet microreactors also enable simple visualization of the HAp formation process as well as control over the porosity in the HAp that is synthesized. Powder formed with our technique demonstrates a remarkable microstructure, as well as significantly enhanced BET specific average surface area and nanoscale porosity. Our results present a novel synthesis approach for controlling the nanoscale porosity and the morphology of inorganic particles using double emulsion droplets.