1. Departments of Chemical Engineering and Materials, University of California Santa Barbara, Santa Barbara, California 93106, Advanced Medical Device Center, ASAHI KASEI Corporation, 1-105 Kanda, Chiyoda-ku, Tokyo 100-8101, Japan, Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, and Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan