A planar micro-sensor for bio-impedance measurements

The outermost layer of the human skin, the stratum corneum (SC), is comprised of structurally inter-positioned anatomical regions. This inter-positioning renders the electrical characterization of its individual region difficult. To address this difficulty, the SC's electrical properties at the cellular level were investigated. Impedance measurements were performed using a planar microelectrode sensor, which was dimensionally comparable in diameter to individual SC corneocytes. In this study, the SC was characterized by detecting micro-heterogeneity within the tissue architecture. The magnitude of the impedance and equivalent parallel capacitance of the SC specimens were measured by applying current to a specified electrode and measuring the resultant voltage potential from its corresponding electrode. Raw data show that the SC impedance at different frequencies depicted a linear approximation which does not fit the Cole-Cole model. These data also suggest that this sensor could be used to probe the molecular structure of the skin. (c) 2005 Elsevier B.V.. All rights reserved.