1. a Bioengineering Unit , University of Strathclyde , Wolfson Centre, 106 Rottenrow, Glasgow, G4 0NW, UK
2. b Department of Design , Manufacture and Engineering Management, University of Strathclyde , James Weir Building, 75 Montrose Street, Glasgow, G1 1XJ, UK
3. c School of Health , Glasgow Caledonian University , Cowcaddens Road, Glasgow, G4 0BA, UK