Method to generate micro scale gas filled liquid bubbles as tracer particles or inhaler mist for drug delivery

Abstract

A method and apparatus that enables the production of micron-scale free-standing bubbles made of liquids containing surfactants are provided. The method and apparatus of the invention overcomes the limitations of conventional bubble forming techniques by using a controlled cavitation process in a liquid media.

1 . A method of generating free-standing micron-scale bubbles comprising:
 providing a solution containing at least one surfactant such that the solution has a surface tension lower than that of pure water;   pressurizing the solution such that a concentration of gas is dissolved therein   atomizing and depressurizing said pressurized solution by releasing said solution into a region of lower pressure to generate a plurality of micron-scale bubbles, wherein the pressure differential between the pressurized and depressurized solution is sufficient to ensure cavitation of the solution occurs.   
     
     
         2 . The method of  claim 1 , wherein the solution contains a surfactant selected from the group consisting of soap, detergent and SDL. 
     
     
         3 . The method of  claim 1 , wherein the solution is pressurized to a pressure of at least 2000 psi. 
     
     
         4 . The method of  claim 1 , wherein the lower pressure region is at an atmospheric pressure. 
     
     
         5 . The method of  claim 1 , wherein the bubbles are on the order of about 10 microns in size. 
     
     
         6 . The method of  claim 1 , wherein the step of pressurizing is accomplished via one of either an air compressor or a reciprocating piston. 
     
     
         7 . The method of  claim 1 , wherein the step of atomizing is accomplished via a nozzle through which the solution is directed. 
     
     
         8 . The method of  claim 7 , wherein the nozzle has an orifice of 1 mm or less. 
     
     
         9 . The method of  claim 1 , wherein the bubbles have a lifetime of at least 10 minutes. 
     
     
         10 . The method of  claim 1 , further comprising a step of gasifying the solution prior to depressurization. 
     
     
         11 . An apparatus for generating free-standing micron-scale bubbles comprising:
 a reservoir defining a volume into which a solution may be disposed, the solution containing at least one surfactant such that the solution has a surface tension lower than that of pure water;   a pressure generator in fluid communication with said reservoir for pressurizing said solution to a pressure sufficient to dissolve a concentration of gas into said solution;   an outlet in fluid communication between the reservoir and a region of low pressure; and   wherein the pressure differential between the pressurized reservoir and the region of low pressure is sufficiently large to induce cavitation in the solution such that a plurality of micron scale bubbles are formed from the solution.   
     
     
         12 . The apparatus of  claim 11 , wherein the solution contains a surfactant selected from the group consisting of soap, detergent and SDL. 
     
     
         13 . The apparatus of  claim 11 , wherein the solution is pressurized to a pressure of at least 2000 psi. 
     
     
         14 . The apparatus of  claim 11 , wherein the lower pressure region is at an atmospheric pressure. 
     
     
         15 . The apparatus of  claim 11 , wherein the bubbles are on the order of about 10 microns in size. 
     
     
         16 . The apparatus of  claim 11 , wherein the pressure generator is one of either an air compressor or a reciprocating piston. 
     
     
         17 . The apparatus of  claim 11 , wherein the outlet includes an atomizing nozzle. 
     
     
         18 . The apparatus of  claim 17 , wherein the nozzle has an orifice of 1 mm or less. 
     
     
         19 . The apparatus of  claim 11 , wherein the bubbles have a lifetime of at least 10 minutes. 
     
     
         20 . The apparatus of  claim 11 , wherein the apparatus further comprises a device for gasifying the solution, the device in fluid communication between the reservoir and the nozzle such that the solution is gasified prior to depressurization.