Mist Generator Kelly Toy Jon Cappel Joe Bothwell Abdikarim Mahamud Advisor – John Webster Client – Jack Jiang, MD, PhD tents/06.00/ asp. tents/06.00/ asp.

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 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 ( uses) t/ Open/

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.

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 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

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 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 Nebulizer Our Device PurchaseAccuracy569 Complexity (ease of use) 583 Price571 Life span 667 Total252620

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 Hess D. Nebulizers: Principles and Performance. Respiratory Care. 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 m 2004 Aerogen,