Department of Mechanical Engineering, University of Zaragoza, Zaragoza, Spain.|Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.|Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.|Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.|Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.|Department of Mechanical Engineering, University of Zaragoza, Zaragoza, Spain.|Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.|Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.