AVS 51st International Symposium
    MEMS and NEMS Monday Sessions
       Session MN-MoM

Paper MN-MoM10
Mechanical and Electrochemical Characterization of Gold Membranes on a Drug Delivery MEMS Device

Monday, November 15, 2004, 11:20 am, Room 213C

Session: Processing and Characterization for MEMS and NEMS
Presenter: Y. Li, Massachusetts Institute of Technology
Authors: Y. Li, Massachusetts Institute of Technology
M.J. Cima, Massachusetts Institute of Technology
Correspondent: Click to Email
Our drug delivery MEMS device was designed to release multiple substances with complex profiles in order to maximize the efficacy of drug therapies. The device consists of arrays of microreservoirs etched into a silicon substrate to contain different types and doses of drug. The release of drug is achieved through the electrochemical dissolution of the gold membranes that seal individual reservoirs. The mechanical and electrochemical properties of the gold membranes are important parameters in evaluating the reliability of device performance. A bulge test apparatus was constructed to measure the mechanical properties of the gold membranes. The apparatus is pressurized, and the resutling deflection of the membranes is measured using interferometry. The biaxial modulus of elasticity and residual stress in the membranes extracted from the bulge test were 126-168 GPa and ~100 MPa (tensile) respectively for membranes with in-plane sizes ranging from 20 to 200 mm. An in situ experimental set up was constructed to observe the electrochemical disintegration process of the gold membranes when voltage was applied. The bulge test was used to evaluate the mechanical integrity of gold membranes corroded for different duration of time. The decrease in the membrane burst pressure with longer corrosion time under the bulge test confirmed a gradual loss of mechanical integrity of the gold membranes due to corrosion. Observation of the membrane morphology with an optical profiler indicated an abrupt transition in the membrane stress state from slightly tensile to highly compressive after five seconds of corrosion. This suggests that the gold membrane disintegration occurs by a combination of thinning through active dissolution and accumulation of compressive stress.