1. Department of Materials Science and Engineering; Frederick Seitz Materials Research Laboratory; University of Illinois at Urbana-Champaign; Urbana IL 61801 USA
2. Electronic and Imaging Materials Research Laboratories; Toray Industries, Inc.; Otsu Shiga 520-0842 Japan
3. Department of Electronic Engineering; Tsinghua University; Beijing 100084 China
4. Department of Materials Science and Engineering; Northwestern University; Evanston IL 60208 USA
5. L'Oréal California Research Center; San Francisco CA 94107 USA
6. Departments of Biomedical Engineering, Chemistry, Neurological Surgery, Mechanical Engineering; Electrical Engineering and Computer Science; Simpson Querrey Institute and Feinberg School of Medicine; Center for Bio-Integrated Electronics; Northwestern University; Evanston IL 60208 USA