Electro-Quasistatic Animal Body Communication for Untethered Rodent Biopotential Recording

Shreeya Sriram,Shreyas Sen,Matthew P Ward,Shitij Avlani

doi:10.1038/s41598-021-81108-8

Abstract

Continuous multi-channel monitoring of biopotential signals is vital in understanding the body as a whole, facilitating accurate models and predictions in neural research. The current state of the art in wireless technologies for untethered biopotential recordings rely on radiative electromagnetic (EM) fields. In such transmissions, only a small fraction of this energy is received since the EM fields are widely radiated resulting in lossy inefficient systems. Using the body as a communication medium (similar to a ’wire’) allows for the containment of the energy within the body, yielding order(s) of magnitude lower energy than radiative EM communication. In this work, we introduce Animal Body Communication (ABC), which utilizes the concept of using the body as a medium into the domain of untethered animal biopotential recording. This work, for the first time, develops the theory and models for animal body communication circuitry and channel loss. Using this theoretical model, a sub-inch^3 [1″ × 1″ × 0.4″], custom-designed sensor node is built using off the shelf components which is capable of sensing and transmitting biopotential signals, through the body of the rat at significantly lower powers compared to traditional wireless transmissions. In-vivo experimental analysis proves that ABC successfully transmits acquired electrocardiogram (EKG) signals through the body with correlation >99% when compared to traditional wireless communication modalities, with a 50times reduction in power consumption.

Highlights

Chronic monitoring of biopotential signals has paved the way for a better understanding of neural pathways along with improved therapeutic treatments
Animal Body Communication was explored as a new modality for the transmission of biopotential signals
The sensing and transmitting devices are built using off the shelf components and consist of a communication module, a processing module, a power source, and an interface to connect it to the rat body

Summary

Introduction

Chronic monitoring of biopotential signals has paved the way for a better understanding of neural pathways along with improved therapeutic treatments. Wireless recording systems have since evolved from discrete modules to system on chip devices These small form-factor wireless devices eliminate the bias introduced by the tethered systems; it is limited by the high-power consumption due to the need for up-conversion of the baseband signal to higher radio frequencies[2] and loss due to radiative communication. We introduce a novel communication modality that uses the animal body as a medium to transmit information This system eliminates the bias introduced by the tethered systems and has a significant size, weight, area, and power benefits compared to electromagnetic communication systems. We transmit the signals using Bluetooth as a method to compare the ABC transmitted signal with an established communication modality In this pilot study, we use the concept of body communication and extend it into the animal domain enabling long term benefits in energy consumption along with size, weight, and area benefits.

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Conclusion