1 Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA, USA. iskang@mit.edu.
2 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
3 Omnisens SA, Morges, 1110, Switzerland.
4 Singapore-MIT Alliance for Research and Technology (SMART) Centre, 1 Create Way, Singapore, 117543, Singapore.