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Mist Generator. http://www.rcjournal.com/contents/06.00/06.00.0609.asp. Kelly Toy Jon Cappel Joe Bothwell Abdikarim Mahamud. Advisor – John Webster Client – Jack Jiang, MD, PhD. Overview. Problem Statement Background Material

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mist generator

Mist Generator


Kelly Toy Jon Cappel

Joe Bothwell Abdikarim Mahamud

Advisor – John Webster

Client – Jack Jiang, MD, PhD

  • Problem Statement
  • Background Material
  • Summary of product design specifications
  • Design Alternatives considered
  • Future Work
problem statement
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
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
  • Different ways to generate mist:
    • Ultrasonic Nebulizer
    • Micropumps
    • Pressure activated devices
  • Particle measurement techniques
ultrasonic nebulizer
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
Ultrasonic NebulizerAdvantages/Disadvantages


  • Stable particle size
  • Small dead volume
  • High aerosol output
  • Quiet
  • Fast drug delivery


  • Aerosol solution can become heated
  • Expensive
  • Short cycle life (600-1000 uses)
  • 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
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


pressure activated devices1
Pressure Activated Devices
  • Devices similar to hairspray bottles
    • Use pressure to compress liquid
    • Liquid is compressed through tiny opening creating mist



pressure activated devices2
Pressure Activated Devices
  • Advantages
    • Inexpensive
    • Simple
  • Disadvantages
    • Comparatively, very large mist particles
    • Different nozzles needed for different densities
particle measurement techniques
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 techniques1
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
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 alternatives1
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
final design choice
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
Future Work
  • Obtain different sized actuators
  • Develop a method for subjecting liquid to specific pressure levels.
  • Develop a prototype
  • Perform experiments
  • Analyze results.
  • 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.stm 2004
  • Aerogen, 2004 http://www.aerogen.com/