Comments on "Microscale flow visualization"
  We make comments on the presentation of Sinton's paper (Microfluidics and Nanofluidics {\bf 1}: 2, 2004) about the microscale flow visualization since the effects of the roughness along the microfabricated wall upon the current macroflow visualization methods could be significant and cannot be neglected in microdomain and even nanodomain. 
A. Kwang-Hua Chu