AVS 50th International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI-WeP

Paper BI-WeP15
Effects of Surface Treatment and Curing Conditions on Poly(Dimethylsiloxane) Metallization for Retinal Prosthesis

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: M. Maghribi, Lawrence Livermore National Laboratory
Authors: M. Maghribi, Lawrence Livermore National Laboratory
C. Evans, Lawrence Livermore National Laboratory
K.J. Wu, Lawrence Livermore National Laboratory
A.J. Nelson, Lawrence Livermore National Laboratory
Correspondent: Click to Email
Surface properties have a critical impact on the general performance of polymers and elastomers. Surface contamination, such as siloxane surfactants, can alter the surface properties of the material thus affecting the fabrication processes. Inadequately cured poly(dimethylsiloxane) (PDMS) is highly mobile and can cause adhesion failures. In this work we explore how surface treatments and PDMS cure time impacts process development for hybrid retinal implants. For example, oxygen plasma treatment is used to promote wetting of the PDMS surface as well as promoting adhesion. To photolithographically pattern metal traces on PDMS is not a trivial task and fundamental material characteristics must be examined to develop reliable and repeatable fabrication processes. Time of flight secondary ion mass spectrometry (ToF-SIMS) and high resolution X-ray photoemission spectroscopy (XPS) were utilized to reveal the surface chemistry attributed to different surface treatments and curing conditions. ToF SIMS results indicate that the basic molecular and chemical structure of poly(dimethylsiloxane) is altered under O@sub 2@ treatment. Specifically, a strong oxidation reaction to the dimethlysiloxane group occurs, replacing methyl with silanol groups; which is ultimately responsible for the success in metallization. XPS quantitative analysis revealed an oxygen rich surface with significantly increased Si-O bonding. In addition, high-resolution C 1s, O 1s and Si 2p core-level spectra revealed additional C-O and O-Si-O bonding following O@sub 2@ plasma treatment. We conclude from these results that the explanation for the affinity of metals to adhere to the PDMS following O@sub 2@ plasma treatment is due to the reactive Si-O group formed on the surface. This work was performed under the auspices of the U.S. Dept. of Energy by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.