Mist Generator http www rcjournal com con tents 06 00 06 00 0609 asp Kelly Toy Joe Bothwell Jon Cappel Abdikarim Mahamud Advisor John Webster Client Jack Jiang MD PhD Overview Problem Statement Background Material Summary of product design specifications Design Alternatives considered Future Work Problem Statement Research being conducted on the larynx can be benefited by the specific targeting of medication in the respiratory system Specific targeting of medication is difficult to complete accurately The process of atomizing particles is complex Client Requirement Product is needed that can Generate a mist of different densities Generate particle sizes in the range of 0 5 50 microns Adaptable as inhaler Generate mist such that different areas of the respiratory system can be targeted Background Different ways to generate mist Ultrasonic Nebulizer Micropumps Pressure activated devices Particle measurement techniques Ultrasonic Nebulizer Converts electricity into ultrasonic waves Transducer vibrates at frequency of waves 1 3 MHz Higher the frequency smaller droplets Transducer generates ultrasonic fountain of liquid Aerosol delivered by fan or inspiration Creates particles 1 6 microns Dennis J Hendrick D Ultrasonic Nebulizer Advantages Disadvantages Advantages Stable particle size Small dead volume High aerosol output Quiet Fast drug delivery Disadvantages Aerosol solution can become heated Expensive Short cycle life 600 1000 uses http www mabis net Micropumps OnQ is one of the micropumps used in the market for nebulizers contains over a thousand precision formed tapered holes surrounded by a vibrational element plate vibrates over 100 000 times per second It draws liquid through the holes to form consistently sized droplets Problems How to adjust the frequency http www aerogen com Pressure Activated Devices Devices that create mist by using pressure Inhalers use a similar principle hand held portable devices that deliver medication directly to the lungs Uses pressurized canister with chemical propellant http www aaaai org patients allergic c onditions metered dose inhalers stm Pressure Activated Devices Devices similar to hairspray bottles Use pressure to compress liquid Liquid is compressed through tiny opening creating mist http www drugstore com http www atomization de basic htm Physical Pressure Activated Devices Advantages Inexpensive Simple Disadvantages Comparatively very large mist particles Different nozzles needed for different densities Particle measurement techniques Laser Diffraction Method is absolute no need to calibrate instruments Wide range 01 2000 microns Flexibility paint nozzle sprays to dry powder Can measure circulating liquid particles Requires expensive equipment Engine research lab has a Malvern laser diffraction instrument Microscopy Relies on microscope and precision measuring devices Somewhat prone to error due to the judgment of the operator Particle measurement techniques Cascade impactor Progressively filters out smaller particles through a series of tubes Particles accumulate according to their size and the concentrations are analyzed after the experiment Can take a relatively long time to complete Electrozone sensing Changes in capacitance are measured as a charged particle flows through a small opening Extremely difficult near impossible to measure sprays Design Alternatives 1 Modify a Nebulizer Adjust pressure input Adjust vibration frequency Apply a charge to solution Adjust opening size Particle size selector Requires monetary investment Design Alternatives 2 Create our own simple device Use the most simple aspects of fluid mechanics Obtain an actuator and force liquid through it at different pressures 3 Purchase existing components May require slight modifications Extremely expensive Design Decision Matrix Accuracy Nebulizer 5 Our Device Purchase 6 9 Complexity 5 ease of use 8 3 Price 5 7 1 Life span 6 6 7 Total 25 26 20 Final Design Choice Create our own simple device We will force liquid through different sized actuators and experimentally determine what size and pressures will obtain the required particle size Easy to modify if needed Relies only on pressure and actuator opening Future Work Obtain different sized actuators Develop a method for subjecting liquid to specific pressure levels Develop a prototype Perform experiments Analyze results References Basic principals of particle size measurement Dr Alan Rawle Malvern Instruments limited http www tsi com particle products accessories 376060 htm http www atomization de basic htm Physical Hess D Nebulizers Principles and Performance Respiratory Care http www rcjournal com contents 06 00 06 00 0609 asp 2 March 2004 Dennis J Hendrick D Design of drug nebulizers Journal of Aerosol Science 2000 Sep S787 s789 this one is for picture American Academy of Asthma and Allergy Immunity http www aaaai org patients allergic conditions metered dose inhalers st m 2004 Aerogen 2004 http www aerogen com
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