Synopsis
- All the attempts to evaluate the tissue mechanical testing and related protocols will be documented on this page.
Note: The force data will not be filtered.
- Force displacement data will be acquired at 2kHz.
- Load cell will be calibrated at the beginning of the test day.
- Appropriate changes will be made to ["Specifications/ExperimentationTissueMechanics"] once evaluation of protocols is complete.
- Details of testing protocols can be found at ["Specifications/ExperimentationTissueMechanics"]
Repeatability of test protocols
- This exercise will be used to evaluate whether the Mach 1 system can apply the same controls when the test environment is not changed. This will also help to determine whether there was any tissue damage/ altered tissue state during the test (if the controls remain the same).
- Ligament tensile test
- A ligament tensile sample will be tested at 3%, 6% and 9% strain at 20%/s strain rate.
- After the completion of first test, the sample will be allowed to rest in an unloaded state for 30 min.
- The sample will not be removed from the test environment.
- The sample will be tested again at 3%, 6% and 9% strain at 20%/s strain rate.
- The sample will be allowed to rest in an unloaded state for 30 min.
- The sample will be tested at 3%, 6% and 9% strain at 100%/s strain rate.
- The sample will be allowed to rest again in an unloaded state for 30 min.
- The sample will be tested again at 3%, 6% and 9% strain at 100%/s strain rate.
- Cartilage unconfined compression test
- A cylindrical cartilage sample will be tested under unconfined compression at 5%, 10% and 15% strain at 20%/s strain rate.
- After completion of the test, the sample will be allowed to rest in an unloaded state for 30 min.
- The sample will not be removed from the test environment.
- The sample will be tested again at 5%, 10% and 15% strain at 20%/s strain rate.
- The sample will be allowed to rest in an unloaded state for 30 min.
- The sample will be tested at 5%, 10% and 15% strain at 100%/s strain rate.
- The sample will be allowed to rest again in an unloaded state for 30 min.
- The sample will be tested again at 3%, 6% and 9% strain at 100%/s strain rate.
- Cartilage confined compression test
- Sample used for unconfined compression will now be tested under confined compression.
- All steps described above for unconfined compression test will be repeated.
- Cartilage tensile test
- A cartilage tensile sample will be tested at 5%, 10% and 15% strain at 20%/s strain rate.
- After completion of the test, the sample will be allowed to rest in an unloaded state for 30 min.
- The sample will not be removed from the test environment.
- The sample will be tested again at 5%, 10% and 15% strain at 20%/s strain rate.
- The sample will be allowed to rest in an unloaded state for 30 min.
- The sample will be tested at 5%, 10% and 15% strain at 100%/s strain rate.
- The sample will be allowed to rest again in an unloaded state for 30 min.
- The sample will be tested again at 3%, 6% and 9% strain at 100%/s strain rate.
Results
Reproducibility of test protocols
- The goal of this exercise is to evaluate whether repeating the test protocols will produce the same results (evaluated through material property identification) provided the sample was not damaged during testing.
- The samples tested in previous section will be removed from the test set up and stored before being retested.
- Sample dimensions will be measured again before testing.
- Ligament tensile test
- A ligament tensile sample will be tested at 3%, 6% and 9% strain at 20%/s strain rate.
- After the completion of first test, the sample will be allowed to rest in an unloaded state for 30 min.
- The sample will not be removed from the test environment.
- The sample will be tested again at 3%, 6% and 9% strain at 100%/s strain rate.
- Cartilage unconfined compression test
- A cylindrical cartilage sample will be tested under unconfined compression at 5%, 10% and 15% strain at 20%/s strain rate.
- After completion of the test, the sample will be allowed to rest in an unloaded state for 30 min.
- The sample will not be removed from the test environment.
- The sample will be tested again at 3%, 6% and 9% strain at 100%/s strain rate.
- Cartilage confined compression test
- Sample used for unconfined compression will now be tested under confined compression.
- All steps described above for unconfined compression test will be repeated.
- Cartilage tensile test
- A cartilage tensile sample will be tested at 5%, 10% and 15% strain at 20%/s strain rate.
- After completion of the test, the sample will be allowed to rest in an unloaded state for 30 min.
- The sample will not be removed from the test environment.
- The sample will be tested again at 3%, 6% and 9% strain at 100%/s strain rate.
Results
Assessment of desired rates and strain levels
- The data acquired with all the previous tests will be evaluated to make sure the applied rates and strain levels match the desired rates and strain levels.
- Note: A python script is being developed to analyze the data quality as soon as the data is acquired (parameters of interest will be applied rates ans strain levels, expected time taken vs desired time taken, instantaneous and relaxed moduli calculation as well as plotting data to visually inspect data quality).
Results
Zero force (find contact) with and without force filter
- It is recommended to not use any force data filtering during testing data acquisition. However, to find zero force (10gf) for initial length measurement, it may be difficult to measure 10gf without no filtering.
- Using a ligament tensile sample, cartilage compression sample and cartilage tensile sample, 10 readings will be taken (for each sample) for zero force measurement with and without force filter to assess the feasibility of not using a force filter.
- A very slow rate (0.01mm/s) will be used.
Results
Assessment of force and displacement data alignment
- Provided the acquired data is not filtered the displacement and force data should align in time.
- The data acquired with the repeatability and reproducibility tests will be evaluated to make sure the displacements and forces are aligned.
Results
Assessment of positioning of clamps to set zero position
- As the zero position of the clamps for tensile tests is set manually through visual inspection, it may be under or overestimated.
- Currently, the inner edges of the two clamps are brought in the same plane and position is zeroed. To minimize the error, the fixed clamp edge position can be marked with a straight line and the moving edge can then be aligned with the straight line.
- Needs further discussion.
Results
Thickness measurement repeatability and reproducibility
- For this test a ligament tensile sample, cartilage compression sample and a cartilage tensile sample will be used.
- To test repeatability of the procedure, the samples thicknesses will be measured 5 times (each time 5 measurements are taken on the sample and averaged) without moving the sample.
- The thickness will be measured both optically and with the lvdt system.
- Average thickness values and standard deviations will be reported.
- The samples will be taken out of the measuring set ups and put back in after a few hours and all the measurements will be repeated again to check for reproducibility of results (set ups will be re-calibrated before the reproducibility tests).
Results
Length measurement repeatability and reproducibility
- For this test a ligament tensile sample, and a cartilage tensile sample will be used.
- To test repeatability of the procedure, the samples lengths will be measured 5 times
- without removing the sample from the test set up.
- The samples will be taken out of the measuring set up and put back in after a few hours and all the measurements will be repeated again to check for reproducibility of results (set ups will be re-calibrated before the reproducibility tests, i.e. zero position).
Results
Standardization of camera positions using bigger lens
- Needs further discussion