SCANNING ELECTROCHEMICAL MICROSCOPY AS A PROBE OF LOCAL FLUID-FLOW THROUGH POROUS SOLIDS - APPLICATION TO THE MEASUREMENT OF CONVECTIVE RATES THROUGH A SINGLE DENTINAL TUBULE

Scanning electrochemical microscopy (SECM) is shown to be a powerful technique for imaging the rate of fluid flow through porous solids. Using a dentine slice (containing tubules of ca. 2 mu m diameter) as an example, local fluid flow rates and topography of the sample are sequentially mapped in situ by monitoring the transport-limited current for the electrolysis of a target mediator (oxidation of aqueous hexacyanoferrate(ll) as a function of tip position, with and without an applied fluid pressure. It is demonstrated, for the first time, that: (i) rates of fluid flow through dentine vary dramatically at the microscopic level and (ii) the flow rate through a single tubule can be quantified.