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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 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 • Better understanding of the musculoskeletal system • Help create better orthopedic implants
Fabrication of Parylene-Based Strain Gauge Taken from “Parylene-Based Strain Sensors for Bone” Taken from “Parylene-Based Strain Sensors for Bone”
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.
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
PPy Deposition Setup Reference Electrode Silicon Wafer Counter Electrode
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.
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.
Compression Tests • A compression device was created to test the conductive properties of carbon black doped PDMS
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.
Future Work • Characterize PPy deposition parameters and resistivity change with strain. • Conduct compression tests to characterize carbon black doped PDMS.
Acknowledgements • National Science Foundation and UROP • Prof. William C. Tang • Gloria Yang • IM-SURE Fellows • Said Shokair