Dissertations and Theses

Date of Award


Document Type



Biomedical Engineering

First Advisor

Marom Bikson


tin, HD-tDCS, skin safety, conductive electrode gel, anode, cathode, electrode, pain, ring electrodes, silver-silver chloride


The objective of this research thesis is to test the viability of Tin (Sn) ring electrodes as an inexpensive alternative to sintered Silver-Silver Chloride (Ag|AgCl) ring electrodes for High Definition – transcranial Direct Current Stimulation (HD-tDCS). Throughout our initial bench top testing of tin electrodes in combination with a ‘conductive electrode gel’, the passing of a 2mA direct current on agar block showed the formation of white cloud around the anode electrode and a cluster of air bubbles on the cathode. The analysis of pertinent literature indicates that the white milky substance produced during the stimulation at the anode is tin oxide/tin dioxide (SnO/SnO2). Afterwards, skin tolerability and subject sensation, along with the electrode potential, were assessed by stimulating forearms of seven subjects. A direct current of 1mA was administered for 20 minutes with application at the same location for five consecutive days of stimulation using the above mentioned Tin ring electrodes. From our initial pilot studies, visible signs of skin inflammation were generated from repeated stimulation on the same location from HD-tDCS in just two days. Therefore, we investigated the effect of topically applied ‘anti-inflammatory cream’ which resulted in minimal skin irritation after five consecutive days of stimulation. We optimized and developed guidelines on safety issues of HD-tDCS technique for the use of Tin ring electrodes for repeated sessions. This includes the thorough design of the plastic Tin ring electrode holder by maximizing the current density and the implementation of skin safety protocols by pretreating the skin before and after stimulation.



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