Galvanic Brain-Coupled Communication Among Freely Floating Micro-Scale Implants

This paper presents a new communication method between micro-scale freely floating brain implants based on galvanic coupling (GC), called "Brain-Coupled Communication" (BCC). Since the transmission efficiency based on GC is highly dependent on the system’s geometry and the electromagnetic properties of the tissue, finite element models in COMSOL Multiphysics® are employed for characterizing the proposed method. Concurrent scaling of channel length (i.e., the distance between two implants), the inter-electrode distance (on a single implant), and electrode dimensions with a constant ratio down to 2 % of their typical values show an increase in the optimum frequency of the communication by 50 times (from 200 kHz to 10 MHz). This, in turn, yields a substantial increase in the channel bandwidth. The proposed method also shows excellent robustness against misalignment. Up to 60 ° of angular misalignment and 1 mm of lateral displacement result in a voltage-gain attenuation of less than 5 dB and 2 dB, respectively. Furthermore, a negligible shading effect between implants is observed by exploring multi-implant scenarios. Moreover, based on the conducted compliance study, no safety hazards were observed for the intended conditions. In conclusion, the proposed method exhibits a multitude of desirable qualities that position it as an excellent choice for establishing a network of freely floating brain implants.