1. Centre for Nanoengineering and Advanced Materials, University of Johannesburg, Johannesburg 2028, South Africa
2. Department of Mechanical and Aeronautical Engineering, University of Pretoria, Pretoria 0024, South Africa
3. Department of Medical Research, China Medical University Hospital, China Medical University, Taichung 400, Taiwan
4. Department of Mechanical and Mechatronic Engineering, Stellenbosch University, Stellenbosch 7600, South Africa