Towards noninvasive bioimpedance sensor design based on wide bandwidth ring resonator

Miniature and noninvasive sensors play a major role in healthcare, by monitoring vital health parameters in real time. Furthermore, energy efficiency is an important issue in human-centric embedded systems. In this paper we describe a new approach for a contact-less bioimpedance measurement. The basic idea stems from the permittivity measurement of electronic circuit substrate. A common procedure in this case is to design and fabricate a substrate with a given resonator structure where the dielectric constant can be calculated from the measured resonant frequency and known resonator geometry and substrate thickness. Similar principle can be employed for bioimpedance measurement. The resonator can be designed such that the resonant frequency lies within the responsive range of the target tissue where the resonant frequency changes are highest following physiological processes. The changed value of the frequency reflects the dielectric properties of the target object. The measured frequency thus implicitly reflects biological and physiological processes within the target object. Some preliminary experiments are described in this paper.