1. Department of Anesthesiology and Critical Care, Medical Center—University of Freiburg, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
2. Department of Bioengineering, Imperial College London, London SW7 2AZ, Great Britain, U.K.
3. Freiburg Materials Research Center (FMF), University of Freiburg, 79104 Freiburg, Germany