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Mechanical characterization of contact lenses by microindentation: Constant velocity and relaxation testing

Paper ID Volume ID Publish Year Pages File Format Full-Text
1590 86 2008 9 PDF Available
Title
Mechanical characterization of contact lenses by microindentation: Constant velocity and relaxation testing
Abstract

Non-destructive methods for testing material properties allow for multiple tests to be performed on the same sample, which will speed up the design and testing process for hydrogel contact lenses. The mechanical properties of contact lenses were investigated by microindentation testing. Indenter force responses were recorded for two modes of testing: constant velocity and relaxation indentation. From these tests, we characterized the biphasic properties of a hydrogel contact lens: Young’s modulus of the solid matrix and hydraulic permeability. Measured indenter force response was fit to finite element (FE) simulation results over a range of Young’s modulus (E) and hydraulic permeability (k) over a short testing time scale (2 s). Estimated hydraulic permeability, 1–5 × 10−15 m4 (N s)−1, was similar to previously measured values for Etafilcon A. However, values determined for Young’s modulus, 50–60 kPa, were lower than previously measured.

Keywords
Hydraulic conductivity; pHEMA-MAA; Poroelastic; Polymer; Hysitron
First Page Preview
Mechanical characterization of contact lenses by microindentation: Constant velocity and relaxation testing
Publisher
Database: Elsevier - ScienceDirect
Journal: Acta Biomaterialia - Volume 4, Issue 5, September 2008, Pages 1560–1568
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering