Optimal electrolytic chloriding of silver ink electrodes for use in electrical impedance tomography.
The electrode-electrolyte interface impedance may be simplistically modelled by an equivalent circuit comprising a resistance, RTOTAL, in series with an empirical, constant phase angle impedance, ZCPA. This pseudo-capacitance can be thought of as representing empirically the non-faradaic, double layer capacitance in the presence of specific adsorption and surface roughness effects. RTOTAL is the sum of the lead and electrolyte resistances. Depositing a thin layer of silver chloride on silver electrodes can yield improved electrical performance characteristics (potential and impedance) when used in conjunction with a chloride gel. An electrolytically deposited AgCl layer tends to have a rough surface profile thus leading to an increase in the effective interface area. This gives rise to a decrease in RTOTAL and ZCPA, both of which are desirable. Unfortunately AgCl is a relatively poor conductor. Increasing layer thickness causes RTOTAL to increase, thus adversely affecting the inter-electrode impedance at high frequencies. Electrode systems for use in electrical impedance tomography therefore require only relatively thin layers of AgCl.
McAdams
E T
ET
Northern Ireland Bio-Engineering Centre, University of Ulster, Jordanstown, Co Antrim, UK.
Henry
P
P
Anderson
J M
JM
Jossinet
J
J
D004553:Electric Conductivity; D004566:Electrodes; D006801:Humans; D012834:Silver; D018030:Silver Compounds; D014054:Tomography / Q000295:instrumentation / Q000379:methods*
D018030:Silver Compounds; D012834:Silver; C037548:silver chloride