Measurements of local flow fields using glass micro-electrodes

Abstract

Local ion distributions in micro- and nanochannels are influenced by electrical charges and electric fields near wall surfaces, and the behavior of ions is different from that in bulk solutions. Using such unique characteristics, novel sensors and energy converters have been developed, such as pH sensors and electric double-layer capacitors. In the present study, we developed glass micro-electrodes, which has a double-barreled structure, for a small sensor of ionic current responses to liquid flows. A glass micro-electrode showed a diode characteristic due to its ion selectivity, and it was usually sensitive to cation transport. A sub micrometer-sized pore at the tip of electrodes was exposed to a liquid flow in a fluidic channel, and an electric potential was measured under a constant current condition maintained by a galvanostat. When a liquid flow was changed, the electric potential difference increased, responding to the flow rate. It was suggested that the resistivity between glass tips was modulated by a liquid flow, which was sensed by ionic current responses. The proposed glass micro-electrode will shed light on the development of measurement techniques for local flow fields.