Integrating superparamagnetic nanoparticles into microsensor circuits for ultra-low-frequency powering/communication towards deep in vivo sensing

抄録

Most in vivo microcircuit-based sensors operate at the low GHz range, which poses challenges for near-field energy transfer from an external source and communication through the dissipative nature of biological tissue. The ideal electromagnetic transmission can be achieved by ultra-low-frequency magnetic fields (1 kHz) that penetrates completely with negligible interaction with tissue. To enhance implementation, we propose to integrate biocompatible, clinically-approved superparamagnetic iron oxide particles into the circuit. Superparamagnetism produces strong magnetic signal at low frequency magnetic fields and is very sensitive to amplitude-changes from the external magnetic source. By connecting a microcoil with SPIOs inside, changes in sensor resistance modulates the total circuit resistance and thus the amount of inductive shielding the microcoil applies on the SPIO (the `felt` amplitude). This reduces the superparamagnetic signal as sensor resistance decreases. Our proof-of-concept work suggests new approaches for the advancement of ultra-low-frequency in vivo microcircuit sensors.