A Wirelessly-Powered Homecage With Segmented Copper Foils and Closed-Loop Power Control

A new wireless electrophysiology data acquisition system, built around a standard homecage, is presented in this paper, which can power up and communicate with sensors and actuators/stimulators attached to or implanted in small freely behaving animal subjects, such as rodents. Key abilities of the energized homecage (EnerCage) system is enabling longitudinal experiments with minimal operator involvement or interruption, while providing test subjects with an enriched environment closer to their natural habitat, without the burden of being tethered or carrying bulky batteries. The magnetic resonant multi-coil design used in the new EnerCage-HC2 automatically localizes the transmitted electromagnetic power from a single transmitter (Tx) coil at the bottom of the cage toward the receiver coil (Rx), carried on/in the animal body, obviating the need for tracking the animal or switching the coils. In order to increase the resonators’ quality factor
$(Q > 166)$
at the desired operating frequency of 13.56 MHz, while maintaining a high self-resonance frequency
$(\text{SRF} > 42\ \text{MHz})$
, they are made of wide copper foils and optimally segmented based on a set of design rules that can be adopted for experimental arenas with different shapes and dimensions. The Rx rectified voltage is regulated at a user-defined window
$(4.1\pm 0.3\ \text{V})$
by a Tx-Rx closed-loop power control (CLPC) mechanism that creates a volume inside the homecage with 42 mW of power delivered to the load (PDL), and a homogeneous power transfer efficiency (PTE) plane of 14% on average at ∼7 cm height, plus stability against angular mis-alignments of up to 80°.