The thin film transistor has a non-transparent structure besides and insulated with the gate. When used in a fiber network, and more particularly, in a metro network, the deleterious effects of optical amplification are reduced. An array of nanochannels spans the junction member and provides fluid communication between the electrolyte solution and the sample solution. A proper dynamic pressure generating means is formed on at least one of the inclined dynamic pressure surfaces of the shaft bush and bearing sleeve.