Wireless Fully Passive Multichannel Recording of Neuropotentials Using Photo-Activated RF Backscattering Methods

Fully passive RF backscattering for wireless monitoring of neuropotentials, electrical activity generated by neurons, is a promising recording technique that may subdue some of the safety restraints observed in traditional active or passive recording schemes. The fully passive device operates without power supply or regulating elements and exhibits a highly simplified implant circuit topology. However, a critical challenge is its current limitation to single channel recording. Here, a method of integrating multiple channels onto the fully passive system is demonstrated that preserves its fully passive qualities and a single shared antenna. Multichannel recording is implemented by introducing photo-selective and photo-sensitive switches to individual channel electrodes to control the activation of individual recording operations via an external multi-band light source. These multi-modal wireless processes are simulated and implemented on Pyrex substrates that demonstrate recording of emulated neuropotential signals as low as V_m ∼ 0.7 mV_{rm pp} with at least 10-dB channel isolation as tested in air.