# US 10,946,148 B2 · Method and apparatus for the production of microscale bubbles by depressurization cavitation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,946,148 B2 - Document ID: US10946148B2 - Status: Granted - Kind: B2 - Application number: 16/134,136 - Filed: 2018-09-18 - Published: 2019-01-17 - Granted: 2021-03-16 - Earliest claimed: 2010-04-20 - Assignees: California Institute of Technology - Applicants: California Institute of Technology - Inventors: Morteza Gharib; Daegyoum Kim - Web page: https://patentgrep.com/patent/US10946148B2 ## CPC - A61M 11/00: Sprayers or atomisers specially adapted for therapeutic purposes (in general B05B; {aerosol containers B65D83/14}) - A61M 11/007: {Syringe-type or piston-type sprayers or atomisers} - B05B 7/0018: {with devices for making foam} - A61M 2202/0468: non-physiological - A61M: DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY (introducing media into or onto the bodies of animals A61D7/00; means for inserting tampons A61F13/26; devices for administering food or medicines orally A61J; containers for collecting, storing or administering blood or medical fluids A61J1/05); DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY (surgery A61B; chemical aspects of surgical articles A61L); DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR {(Electrotherapy, e.g. producing anaesthesia by the use of alternating or intermittent currents A61N1/36021)} - B05B: SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES (spray-mixers with nozzles B01F25/72; processes for applying liquids or other fluent materials to surfaces by spraying B05D) ## 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. ## Claims ### Claim 1 A method of producing free-standing micro-scale bubbles by using a controlled cavitation process comprising: providing an aqueous solution have a solution density (p) and containing a concentration of at least one surfactant such that the aqueous solution has a surface tension lower than that of pure water; disposing the solution within a pressurizing vessel defining an inner volume and having at least one gas conduit and at least one fluid outlet in fluid communication with the inner volume, wherein the at least one fluid outlet has an atomizing misting nozzle disposed at an outlet thereof disposed external to the pressurizing vessel; introducing a gas into the pressurizing vessel through the at least one gas inlet; pressurizing the pressurizing vessel to an internal pressure (p) such that a concentration of the gas is dissolved within the solution to form a pressurized solution having a solution vapor pressure (pv) of the gas disposed therein; wherein the internal pressure is at least 2000 pound-force per square inch, psi; opening the outlet to a low pressure gaseous region having a local pressure, wherein the force imparted on the pressurized solution by the pressure differential between the internal pressure and local pressure causes the pressurized solution to flow from the inner volume of the pressurized vessel through the atomizing misting nozzle of the at least one fluid outlet to the low pressure region at a flow velocity (V) sufficient to form an atomized mist of droplets of the solution in the low pressure gaseous region; wherein the at least one surfactant is selected from the group consisting of soap, detergent and sodium lauryl sulfate; wherein the pressurized gas has a concentration (c) and the concentration and the solution vapor pressure satisfy Henry's law: pv=kHc and kH is Henry's law constant; wherein the solution density, the pressure differential between the solution vapor pressure of the atomized mist and the local pressure of the low pressure region, and the velocity of the atomized mist at the atomizing mist nozzle of the outlet are configured to produce a cavitation number (Ca) in the droplets of less than 1 as given by the equation: C = p - p v 1 ⁢ / ⁢ 2 ⁢ ρ ⁢ ⁢ V 2 such that the cavitation occurs within the droplets of the atomized mist to produce a plurality of free-standing solution bubbles in the gaseous atmosphere of the low pressure region; and wherein the bubbles have a lifetime of at least 10 minutes. ### Claim 2 (depends on 1) The method of claim 1, wherein the local pressure is 1 atm. ### Claim 3 (depends on 1) The method of claim 1, wherein the internal pressure is at least 2200 psi, the local pressure is 1 atm, the atomizing misting nozzle has an orifice opening size of 1 mm or less, and the bubbles are on the order of about 10 microns in size. ### Claim 4 (depends on 1) The method of claim 1, wherein the step of pressurizing is accomplished via one of either an air compressor or a reciprocating piston. ### Claim 5 (depends on 1) The method of claim 1, wherein the atomizing misting nozzle has an orifice opening size of 1 mm or less. ### Claim 6 (depends on 1) The method of claim 1, wherein the atomizing misting nozzle has an orifice opening size of 0.25 mm or less. ### Claim 7 (depends on 1) The method of claim 1, wherein the solution has a ratio of surfactant to water of at least 1:2. ### Claim 8 A method of producing free-standing bubbles comprising: providing an aqueous solution have a solution density (ρ) and containing a concentration of at least one surfactant in a ratio of surfactant to water of at least 1:2, such that the aqueous solution has a surface tension lower than that of pure water; disposing the solution within a pressurizing vessel defining an inner volume and having at least one gas conduit and at least one fluid outlet in fluid communication with the inner volume, wherein the at least one fluid outlet has an atomizing misting nozzle having an orifice opening of no greater than 1 mm, disposed at an outlet thereof disposed external to the pressurizing vessel; introducing a gas into the pressurizing vessel through the at least one gas inlet; pressurizing the pressurizing vessel to an internal pressure (p) of at least 2200 psi such that a concentration of the gas is dissolved within the solution to form a pressurized solution having a solution vapor pressure (pv) of the gas disposed therein; opening the outlet to a low pressure gaseous region having a local pressure of around 1 atm, wherein the force imparted on the pressurized solution by the pressure differential between the internal pressure and local pressure causes the pressurized solution to flow from the inner volume of the pressurized vessel through the atomizing misting nozzle of the at least one fluid outlet to the low pressure region at a flow velocity (V) sufficient to form an atomized mist of droplets of the solution in the low pressure gaseous region; wherein the at least one surfactant is selected from the group consisting of soap, detergent and sodium lauryl sulfate; wherein the pressurized gas has a concentration (c) and the concentration and the solution vapor pressure satisfy Henry's law: pv=kHc and kH is Henry's law constant; wherein the solution density, the pressure differential between the solution vapor pressure of the atomized mist and the local pressure of the low pressure region, and the velocity of the atomized mist at the atomizing mist nozzle of the outlet are configured to produce a cavitation number (Ca) in the droplets of less than 1 as given by the equation: C = p - p v 1 ⁢ / ⁢ 2 ⁢ ρ ⁢ ⁢ V 2 such that the cavitation occurs within the droplets of the atomized mist to produce a plurality of free-standing solution bubbles in the gaseous atmosphere of the low pressure region; and wherein the bubbles thus formed are on the order of about 10 microns in size and have a lifetime of at least 10 minutes.