Download Mist Generator

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
University of Wisconsin - Madison
Biomedical Engineering Design Courses
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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.ne
t/40-270-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.
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)
Price
5
8
3
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/