1. Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota.
2. Present address: Intel Corp., Chandler, Arizona.
3. Present address: Centro Nacional de Microelectronica (CNM-IMB, CSIC), Barcelona, Spain.
4. Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota.
5. Departments of Pharmaceutics, and Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota.
6. School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana.