EnerCage: A Smart Experimental Arena With Scalable Architecture for Behavioral Experiments

Abstract

Wireless power, when coupled with miniaturized implantable electronics, has the potential to provide a solution to several challenges facing neuroscientists during basic and preclinical studies with freely behaving animals. The EnerCage system is one such solution as it allows for uninterrupted electrophysiology experiments over extended periods of time and vast experimental arenas, while eliminating the need for bulky battery payloads or tethering. It has a scalable array of overlapping planar spiral coils (PSCs) and three-axis magnetic sensors for focused wireless power transmission to devices on freely moving subjects. In this paper, we present the first fully functional EnerCage system, in which the number of PSC drivers and magnetic sensors was reduced to one-third of the number used in our previous design via multicoil coupling. The power transfer efficiency (PTE) has been improved to 5.6% at a 120 mm coupling distance and a 48.5 mm lateral misalignment (worst case) between the transmitter (Tx) array and receiver (Rx) coils. The new EnerCage system is equipped with an Ethernet backbone, further supporting its modular/scalable architecture, which, in turn, allows experimental arenas with arbitrary shapes and dimensions. A set of experiments on a freely behaving rat were conducted by continuously delivering 20 mW to the electronics in the animal headstage for more than one hour in a powered 3538 cm2 experimental area.

Towards a wireless optical stimulation system for long term in-vivo experiments

“…High-efficiency wireless power transmission links based on inductively coupled coils are used as battery chargers or as short-range standalone wireless power sources [17][18][19][20]. Designing a wireless power transmission link for this application is very challenging since it must be highly efficient and robust to motion and angular misalignments of the power-receiver.…”

“…Wireless power transmission chambers have been designed to power up small electronic systems. The chamber can use a single big coil, the size of the chamber, or an array of smaller coils [17], [19][20][21][22]. Using a chamber the bottom of which is tiled with smaller TX coils has proven much more efficient than one with a single big coil that encompasses the whole area [19][20][21][22].…”

“…In fact, arrays of coils can provide homogeneous magnetic flux density within the entire chamber area. The uniformity of the magnetic field can also be further improved by using multiple overlapped power RX coils [20].…”

“…Power localization focuses the transmitted power at the location of the power RX coil, so no resource is wasted [19][20][21]. Different techniques have been used to avoid driving all coils of an array simultaneously [13], [20][21][22].…”

“…Different techniques have been used to avoid driving all coils of an array simultaneously [13], [20][21][22]. In [20], a magnetic sensor is used to detect the location of a small magnet embedded in the RX and to activate the subset of coils that encompass the RX using dedicated control circuitry. On the other hand, a closed-loop power control mechanism must be utilized to compensate the power variations when the receiver is moved in the z direction.…”