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Micro-Technologies for Implantable Strain Gauge Arrays

Micro-Technologies for Implantable Strain Gauge Arrays. Anais Sahabian William C. Tang Gloria Yang. Implantable Bone Strain Gauges. Advantages: Better understanding of types of strain bones undergo when affected by conditions such as osteoporosis or a tumor

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Micro-Technologies for Implantable Strain Gauge Arrays

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  1. Micro-Technologies for Implantable Strain Gauge Arrays Anais Sahabian William C. Tang Gloria Yang

  2. Implantable Bone Strain Gauges Advantages: • Better understanding of types of strain bones undergo when affected by conditions such as osteoporosis or a tumor • Better understanding of the musculoskeletal system • Help create better orthopedic implants

  3. Fabrication of Parylene-Based Strain Gauge Taken from “Parylene-Based Strain Sensors for Bone” Taken from “Parylene-Based Strain Sensors for Bone”

  4. Thermal Distribution Simulation

  5. Thermal Distribution: Cross-Sectional View

  6. Results • The results were used as a qualitative analysis as opposed to a quantitative one. The simulation could not be done using the actual size of the device because of the lack of memory needed to compute the solutions. • In the real strain gauge, the gold is actually 9 times thinner and the current applied is magnitudes smaller. This means that the strain gauge will only slightly increase in temperature and the tissue and bone surrounding the parylene C will not feel the heat from the gold strain gauge.

  7. Polypyrrole Deposition • Polypyrrole (PPy) is a naturally conductive polymer • Its conductivity changes with strain • Goal: To understand PPy properties so we can make a strain gauge using polypyrrole as the sensing mechanism

  8. PPy Deposition Setup Reference Electrode Silicon Wafer Counter Electrode

  9. After the Deposition

  10. Preliminary Results • After measuring the thicknesses of the PPy-coated wafers a correlation can be seen between amount of current applied and the thickness of the wafer. • Specifically, as the current increases the thickness of PPy deposited onto the wafer increases. • This correlation must be tested further to better understand exactly what currents give rise to certain thickness.

  11. Carbon Black Doped PDMS • PDMS is not naturally conductive, while carbon black is. • When the two are mixed together the PDMS becomes conductive. • This is useful because it can be used as the sensing mechanism in strain gauges.

  12. Compression Tests • A compression device was created to test the conductive properties of carbon black doped PDMS

  13. Components of Setup

  14. Stress vs. Strain Curve

  15. Resistance vs. Strain Curve

  16. Preliminary Results • As expected, when strain increases, the resistance of the PDMS decreases. • This shows that carbon black doped PDMS is sensitive enough to be used in a strain gauge. • The PDMS piece might become deformed after the first cycle, which would explain the decrease in resistance after each cycle.

  17. Future Work • Characterize PPy deposition parameters and resistivity change with strain. • Conduct compression tests to characterize carbon black doped PDMS.

  18. Acknowledgements • National Science Foundation and UROP • Prof. William C. Tang • Gloria Yang • IM-SURE Fellows • Said Shokair

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