New polypyrrole based bio-sensors for Bio-impedance measurement

ABSTRACT

Objective: The main task of this work consists in an obtaining polarizable, dry mode, of bio-impedance sensors for non-invasiveECG monitoring, that work without any skin preparation or gel use, in two constructive models, based on conductive organicpolymer polypyrrole and polypyrrole with Ag nanoparticles (NP), as sensitive materials. Methods: The polypyrrole wassynthetized by chemical oxidative polymerization using FeCl3 as oxidant agent. For sensors fabrication two technological variantshave been chosen, a first variant realized by photolithographic method consisting in a substrate of Printed Circuit Board (PCB)with interdigitated copper electrode with step of 0.25 mm and over a distance of 12 mm and two pads. The polypyrrole orpolypyrrole with Ag NP dissolved in ethyl alcohol was deposed on the substrate by dipping method. The second model consists ina polypyrrole powder pressed at a hydraulic press at 10 tones/cm2 of force where one site was deposed a layer of Ag ink forconduction. Results: The performance of bio-impedance sensors were accessed by impedance skin-sensor interface withfrequency in the range of 10 - 300 kHz measurements. The influences of technological fabrication as shape and geometry as wellas the sensitive materials that used, in terms of impedance were analyzed. Conclusions: The introduction of Ag NP in polypyrrole,led to a better behavior, in terms of conduction and impedance response. For all tested sensors, the impedance decreases with thefrequency with a good linearity.