[1] ETH Zurich, Inst Biomed Engn, CH-8044 Zurich, Switzerland
[2] ETH Zurich, Dept Mat, CH-8044 Zurich, Switzerland
[3] Univ Zurich, Zurich, Switzerland
[4] CALTECH, Div Chem & Chem Engn, Pasadena, CA 91125 USA
[5] Arizona State Univ, Dept Bioengn, Tempe, AZ 85287 USA