1. Council for Scientific and Industrial Research (CSIR), National Laser Centre, Pretoria, South Africa
2. School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4041, South Africa
3. Orthopaedic Biomechanics Lab, Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town, South Africa