We have developed a new leakage current microsensor by using simpler planar processes than Si-surface-bulk micromachining processes used in the previous microwell structure. This sensor fabrication and structure can easily make a target solution volume smaller than mu L with excellent immobilization of the droplet and intact biomolecules as sensing elements, as a result, reduce effectively the background noise current in the microsensor and improve reproducibility of the results. The leakage current due to the biochemical interaction was successfully evaluated, dependent on the droplet protein concentration. Cole-Cole plots from the impedance analysis also show quantitative difference between with and without the interaction, depending on the charge-transfer impedance that results from the condition and structure of liposome and lipid membrane after the interaction. (C) 2011 Published by Elsevier Ltd.