1. Bioengineering, Chemical and Paper Engineering Department; Miami University; Oxford OH 45056 USA
2. Department of Materials Science and Engineering; University of Michigan; Ann Arbor MI 48104 USA
3. Department of Biomedical Engineering; University of Michigan; Ann Arbor MI 48104 USA
4. Department of Biologic and Materials Sciences (Dentistry); University of Michigan; Ann Arbor MI 48104 USA