Peng Liu1, Jiwei Huang2, Shiwu Zhang3, Ronald X Xu3. 1. University of Science and Technology of China, Department of Precision Machinery and Precision Instrumentation, 96 Jinzhai Rd., Hefei, Anhui 230027, China. 2. The Ohio State University, Department of Biomedical Engineering, 1080 Carmack Rd., Columbus, Ohio 43210, United States. 3. University of Science and Technology of China, Department of Precision Machinery and Precision Instrumentation, 96 Jinzhai Rd., Hefei, Anhui 230027, ChinabThe Ohio State University, Department of Biomedical Engineering, 1080 Carmack Rd., Columbus, Ohio 43.