Long-Term Measurements with Ionic Liquid Electrodes

Long-Term Measurements with Ionic Liquid Electrodes

Author: Lisa-Marie Rauschendorfer

Cutaneous electrophysiological recordings are used in clinical tests to measure physiological functions. Most prominent is the electroencephalography (EEG) as it is less invasive and more economical than other neurological methods. The electrodes currently used require the addition of a liquid electrolyte to decrease the high impedance between the electrode and skin that makes long-term diagnostics impossible as dehydration occurs after a few hours.

George G. Malliaras, Ecole Nationale Supérieure des Mines, Gardanne, France, and colleagues analyzed ionic liquid (IL) gels for electrodes. ILs are salts that are liquid at room temperature. They are characterized by a high chemical and thermal stability and by an excellent conductivity. The IL gel was incorporated on electrodes of Au and of the conducting polymer poly(3,4-ethlendioxythiophene) doped with poly(styrene sulfonate) (PEDPT:PSS). This electrode was tested in cutaneous recordings on a healthy volunteer (see picture; R.E.= reference electrode; C.E.= counter electrode). Whereas the commercial electrode’s impedance dramatically increased after only one day owing to dehydration, the impedance of the IL gel electrode remains the same for three days. Therefore, the IL gel-assisted electrodes provide the means for long-term diagnostic procedures.

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