[1] Texas A&M Univ, Dept Elect & Comp Engn, College Stn, TX 77843 USA
[2] Univ Calif San Diego, Dept Mat Sci & Engn, San Diego, CA 92093 USA
[3] Korea Inst Sci & Techonol, Biomat Ctr, Seoul 136791, South Korea
[4] Seoul Natl Univ, Dept Mat Sci & Engn, Seoul 151742, South Korea
[5] Korea Inst Sci & Technol, Future Convergence Technol Ctr, Seoul 136791, South Korea