1. Department of Mechanical EngineeringMassachusetts Institutes of Technology 500 Technology Square MIT Building, Room NE47‐321 Cambridge MA 02139 USA
2. Department of Mechanical and Aerospace EngineeringPolitecnico di Torino Corso Duca degli Abruzzi 24 10129 Torino Italy
3. Department of Biological EngineeringMassachusetts Institutes of Technology 500 Technology Square, MIT Building, Room NE47‐321 Cambridge MA 02139 USA