Tribology Laboratory |
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The materials and geometric designs of hydrogels often dictates their performance as soft contact lenses in a human eye, as well as the experimental values of friction when tested. New materials must be critically examined, especially their frictional behavior in ocular conditions. Additionally, non-destructive methods of validating designed material properties will allow for multiple material-property tests to be performed on the same sample, which will speed up the design and testing process for hydrogel contact lenses. Previously, we have measured relative friction between different types of hydrogels and developed a model for the mechanisms of friction in these measurements. We have also performed a non-destructive indentation tests and validated material properties.
 Material properties of soft materials can be obtained in various ways. Traditionally, a dog-bone test has been used to obtain a stress/strain curve in which the ‘coupon’ sample is stretched until failure, with deformation and applied force measured continuously. By using a least squares regression line on the stress/strain curve, an effective elastic modulus can be calculated. This method uses a large sample of hydrogel, and the sample then cannot be used for additional testing because it has been stretched to failure. Another way to obtain material properties is to indent a material and fit the penetration/force curve to a contact model. |
