1. Mechanical Testing System Coupled with an Environmental Chamber for Hydrogels Team: Charlie Haggart, Gabriel J. Martínez-Díaz, Darcée Nelson, and Michael Piché Client: Weiyuan John Kao, Ph.D. Advisor: Paul Thompson BME 402 Midsemester Presentation 3/7/03

2. Overview Problem Statement Background Information Previous Work Current Progress Future Work Acknowledgements

3. Problem Statement To design and build an environmental chamber to be used with a mechanical testing system to observe the tensile and creep properties of hydrogels under varying physiological conditions

4. Background Information Hydrogels  Cross-linked polymeric structures  Can absorb water or biological fluids  Properties change with pH and temperature  Applications include drug delivery vessels and wound/burn care

5. Design Specifications Mechanical properties of hydrogels must be characterized in physiological conditions (pH = 4-8 and 37 °C) Interested in tensile and creep properties to understand the behavior of hydrogels in varying conditions

6. Previous Work: Tensile Testing Environmental chamber was built to be used with Instron 1000

7. Previous Work: Creep Testing Instron 1000 incapable of creep testing No other commercially available devices exist Creep chamber was built last semester

8. Present Work: Tensile Testing Conducted tensile testing with environmental chamber and Instron 1000 Environmental chamber met specifications (maintained physiological conditions, compatible with Instron 1000)

9. Present Work: Tensile Testing Instron 1000 not sensitive enough to measure tensile properties of hydrogels tested System may be used for future testing  Different materials (i.e. rat skin)

10. Present Work: Creep Testing Problem  Grips were difficult to adjust Solution  New grips were ordered from McMaster-Carr 1“

11. Present Work: Creep Testing Problem  Chamber too small to fit hands into, making sample adjustment difficult Solution  Modified tensile chamber, in order to be used for tensile AND creep tests

12. Present Work: Creep Testing Acrylic cylinder to stabilize LVDT Weight stand Chamber positioned onto creep base Acrylic cylinder added that forms tight seal with o- ring Bottom grip attached Pulley system will be added here

13. Future Work Modify grips for use in creep testing system Attach pulley apparatus Data acquisition Validation of creep testing system

14. Acknowledgements Professor Kao Paul Thompson Bill Hagquist, ME Shop Jeff Schowalter, ECE Dept. BME Dept.