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.

3. 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

5. Initial Concepts • One of these concepts is sketched below Figure 2: Concept 2

6. 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 Figure 3: Solid Model of the Clip

7. 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

8. 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 Figure 5: Base with mounting sub-assembly

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 Figure 6: RRA-23 Linear Actuator

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 Figure 7: Strain Gage Figure 8: 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

12. 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

13. 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 sensor’s signal and may need replacement

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