Acknowledgments
M. Wang thanks Hong Kong’s Research Grants Council (RGC) for the financial support for this work through research grants 17200519, 17202921, 17201622 and N_HKU749/22 and also The University of Hong Kong (HKU) for research grants in its Seed Fund for Basic Research Scheme. S. Chen and J Lai thank HKU for providing them with PhD scholarships. Assistance provided by members of M. Wang’s research group and by technical staff in HKU’s Department of Mechanical Engineering, Faculty of Dentistry and Electron Microscopy Unit is acknowledged.