Stretching machine for biomedical research

1
Stretching machine for biomedical research

• Mark Bradford
• Kevin Feeley
• Tony Martinelli
• Jeff Snyder
• Jacob Stephens

2
Background

• Our sponsor sought a device capable of recreating
  in vivo conditions on cell cultures.
• This device applies the mechanical stresses and
  strains that a particular type of cell culture
  would encounter within the body.
• There is a device available commercially for this
  purpose however, it is prohibitively expensive.
• The purpose of this project was to design an
  alternative that is less expensive, thus enabling
  more researchers access to this type of machine.

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Customer Requirements

• Must be considerably less expensive to
  manufacture
• Must use standard well plates
• Must be computer controlled
• Must fit in an incubator
• Must tolerate humidity up to 100
• Must be easy to use
• Must allow easy access to well plate
• Must measure forces applied to cultures
• Must measure displacement applied to cultures
• Must have high repeatability

4
Initial Concepts

• Several concepts were brainstormed
• All concepts accomplish same functions but with
  different components
• Those components included the clipping mechanism,
  driver, and type of well plate

Figure 1 Clipping Mechanism Concept
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Initial Concepts

• One of these concepts is sketched below

Figure 2 Concept 2
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Final Design, Clips

• The clips secure the membrane to the stretch
  plate
• The version shown below was determined to be the
  most user-friendly, while accomplishing their
  primary function

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Final Design, Stretch Plate

• The stretch plate transfers force from the driver
  to the membranes
• The final version is designed for standard 8-well
  plates

Figure 4 Solid Model of Stretch Plates
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Final Design, Base

• The base constrains the stretch plate and holds
  the well plate in place
• It was also designed to allow easy removal of the
  well plate

9
Final Design, Driver

• The driver in the final design was picked to be a
  linear actuator
• The driver provides force to stretch the membrane

10
Final Design, Sensors

• Two sensors were needed, one that measured force
  and the other to measure displacement
• The force sensor was a Load Cell strain gage, and
  the displacement sensor was a Baumer Inductive
  sensor

11
Final Design, Software

• The machine needs to be computer controlled, and
  use software that is easy to use
• National Instruments LabVIEW was chosen

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Evaluation

• Concepts

• Final Design

• Clips
• Used staples or screwed-down clamp
• Well Plates
• Used 6-well or 8-well plates
• Driver
• Used solenoid or piezoelectric motors
• Base
• Requires removal of stretch plate to access well
  plate

• Clips
• Uses ridged clamps
• Well Plates
• Uses 8-well plates
• Driver
• Uses electric linear actuator
• Base
• Well plate can be removed without touching
  stretch plate

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Recommendations

• A prototype was produced, but a production run
  would use different materials
• Of particular interest are the polymers whose
  resins are commercially available through
  Solvay?. They provide the necessary mechanical
  properties and environmental stability needed for
  this product.

14
Recommendations

• The displacement sensor may need to be replaced
  with a more accurate linear laser sensor
• The motor might interfere with the force sensors
  signal and may need replacement

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Acknowledgements

• We would like to thank Cook Biotech, Dr. Omar
  El-Mounayri, Dr. Hazim El-Mounayri, and Mr. Rudy
  Earlson.