1. UNC/NCSU Joint Department of Biomedical Engineering, North Carolina State University, 4206D Engineering Building III, 911 Oval Drive, Raleigh, North Carolina 27695-7115, USA
2. Department of Chemical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Road, Da'an District, Taipei City 106, Taiwan
3. Department of Biomedical Engineering, Beckman Laser Institute, University of California Irvine, 1002 Health Services Road, Irvine, California 92617, USA