Sensor-Embedded Tissue-Mimicking Material for Long-Term Transcranial Electrical Stimulation

Experimental transcranial electrical stimulation (TES) research depends on tissue-mimicking materials (TMMs) for a validation of electric field distribution within the human head. Compared to conventional gel-based TMMs, conductive polymer composites, such as PDMS with multi-walled carbon nanotubes (MWCNTs), offer improved shelf-life and stable conductivity. However, integration of embedded sensors for real-time field mapping remains largely unexplored. Here, we present a fabrication method for sensor-integrated TMMs made from doped PDMS, achieving a conductivity of 3.3 S/m at 1.5 wt% doping with MWCNTs, with electrical sensor structures manufactured by photolithography. DC stimulation revealed irreversible resistance increases, highlighting the suitability of AC or pulsed excitation for long-term studies. Voltage distribution mapping within the TMM was achieved through embedded copper sensors, and results were consistent in trend with computational simulations, validating the experimental approach. This work demonstrates the feasibility of sensorintegrated polymer TMMs for TES, ensuring reproducible sensor placement and providing a foundation for advanced brain phantom studies.