Skin Testing Procedure - 1/13/11
Test Set-up:
16mm focal length lenses
Large pressure chamber (attach light ports)
Large (60cc) syringe, MTS stop adjusted to “large syringe”
7.5cm ID fixture, spray painted white, x and y axis marked from template
1” calibration grid target
0. Thaw sample in PBS overnight in fridge
1. Record Room Temp and Humidity
2. Trim off all fat. May have to re-soak at end and trim some more.
3. Measure thickness at edges (top/bottom/left/right) with calipers. Take 3 measurements at each location.
4. Glue specimen to fixture so that head direction is aligned with y-axis marked on fixture. Turn over, trans-illuminate, and mark edges of fixture ID with pen. Score on this side and impregnate with glue. Let dry. Trim excess skin, and add line of glue at boundary. Let dry. (15-30 minutes or until glue changes from purple to clear).
5. Ensure chamber is level. Attach pressure transducer to chamber and support with stand. Ensure cameras are 15” above chamber. Ensure chamber is centered in both fields of view. Zero pressure transducer channel in TestWorks4.
6. Fill syringe with PBS with chamber valve open. Ensure no bubbles in line. Lower syringe until sealed (maintain meniscus). Close valve, fill chamber with PBS. Load sample and secure with 6 screws. Note baseline/bring to 0.04psi.
7. Manually increase pressure to determine when syringe will bottom out (i.e. make sure you can get to 0.8 psi).
8. Speckle sample and fixture with graphite and 60micrometer mesh.
9. Focus cameras (at wide open aperture, 3ms exposure time) on “x-axis” part of fixture. Return to 8/f aperture, 25ms.
10. Swing chamber/transducer out of the way. Turn off lights, put paper on bench, shine lights on paper. Use 1” Calibration Target to take about 20 images. Calibrate system, check C.I. and that error < 0.03. Save as project file w/date.
11. Replace chamber in field of view. Take ~3 images at baseline pressure. Run correlation and ensure good speckle, level, etc.
12. Place Humidity chamber over sample. Place saturated honeycomb and humidity/temp reader inside chamber. Target ~40% (?) humidity.
13. Hold sample at baseline for 15 minutes. (Run Initial15minhold method on Testworks).
14. Ensure Analog data is being read. Start VicSnap acquisition. Start selected TestWorks method.
15. Freeze sample (still on fixture). Wipe everything down with bleach.
Some sample/typical test parameters (see Acta Biomateriala Paper for exact protocols):
Test baseline = 0.04 psi
Max pressure = 0.8 psi
Pressure rate = 0.01 psi/s, 0.1 psi/s
Creep: ramp up at 0.1 psi to ~0.15psi
Correlation/Data Extraction Procedure:
CORRELATION:
1. Select main AOI as close to edges as reasonable (want circle for centering)
a. Use subset =50
b. Select 3 points and “complete”
c. Ensure all images find the point
2. Select 4 more AOIs – rectangles around grid markers on fixture
3. Import calibration
4. Correlate 1-2 images
a. Ensure postprocesing is “none” (not autoplane)
5. Correct stereo sytem (“Callibrate Camera Orientatin”)
6. Recorrelate 1-2 images
7. Select coordinant system (3-point). Save as “3pt-date”
8. Save project, outside of folder containing images.
9. Delete 4 rectangular AOIs
10. Run complete correlation. Record maximum error & error at beginning.
11. Apply transform to all images
DATA EXTRACTION:
1. Extract node data at apex. Make note of node coordinants
NAME: Test#_grid_MM.DD.YY.csv
2. Extract grid data (every 5 pixels) for all images of loading curve
NOTE: Save all data (including project file) to folder above images. Transfer a copy with a flash drive.
NAME: Test#_apex_MM.DD.YY.csv
3. Rename and copy “test.csv” file.
NAME: Test#_MM.DD.YY.csv
