# Magneto-Inductive Powering and Uplink of In-Body Microsensors: Feasibility and High-Density Effects

## TL;DR

This paper explores the feasibility of magneto-inductive wireless power transfer and data uplink for in-body microsensors, demonstrating potential for high-density sensor swarms with cooperative communication strategies.

## Contribution

It introduces a comprehensive magneto-inductive MIMO system model and analyzes the effects of dense sensor swarms, including passive relaying and beamforming, for biomedical applications.

## Key findings

- Minimum coil size of 150 um for sensor activation at 12 cm distance
- Achieves 1 Mbit/s uplink rate with a 275 um coil
- Significant performance gains with adaptive matching and node cooperation

## Abstract

This paper studies magnetic induction for wireless powering and the data uplink of microsensors, in particular for future medical in-body applications. We consider an external massive coil array as power source (1 W) and data sink. For sensor devices at 12 cm distance from the array, e.g. beneath the human skin, we compute a minimum coil size of 150 um assuming 50 nW required chip activation power and operation at 750 MHz. A 275 um coil at the sensor allows for 1 Mbit/s uplink rate. Moreover, we study resonant sensor nodes in dense swarms, a key aspect of envisioned biomedical applications. In particular, we investigate the occurring passive relaying effect and cooperative transmit beamforming in the uplink. We show that the frequency- and location-dependent signal fluctuations in such swarms allow for significant performance gains when utilized with adaptive matching, spectrally-aware signaling and node cooperation. The work is based on a general magneto-inductive MIMO system model, which is introduced first.