1. Division of Chemistry and Chemical Engineering, California Institute of Technology; Pasadena, California 91125, United States
2. Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, United States
3. Andrew and Peggy Cherng Department of Medical Engineering, California Institute of Technology, Pasadena, California 91125, United States
4. Howard Hughes Medical Institute, Pasadena, California 91125, United States