1. Department of Bioengineering Imperial College London 86 Wood Lane London W12 0BZ UK
2. Department of Engineering Mathematics University of Bristol Ada Lovelace Building, University Walk Bristol BS8 1TW UK
3. Bristol Robotics Laboratory T Block, UWE Frenchay Campus, Coldharbour Lane Bristol BS16 1QY UK
4. Department of Mechanical Engineering University of Bristol Queens Building, University Walk Bristol BS8 1TR UK