1. The Biorobotics Institute, Sant'Anna School of Advanced Studies 1 , Viale R. Piaggio 34, 56025 Pontedera, Italy
2. Department of Excellence in Robotics and AI, Sant'Anna School of Advanced Studies 2 , P.zza Martiri della Libertà, 56127 Pisa, Italy
3. Institute of Solid State Physics, NAWI Graz, Graz University of Technology 3 , 8010 Graz, Austria
4. Department of Electrical and Computer Engineering, North Carolina State University 4 , Raleigh, North Carolina 27606, USA
5. Center for Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST), North Carolina State University 5 , Raleigh, North Carolina 27606, USA