Single-Sided Near-Field Wireless Power Transfer by A Three-Dimensional Coil Array

Abstract

Wirelessly powered medical microrobots are often driven or localized by magnetic resonance imaging coils, whose signal-to-noise ratio is easily affected by the power transmitter coils that supply the microrobot. A controlled single-sided wireless power transmitter can enhance the imaging quality and suppress the radiation leakage. This paper presents a new form of electromagnet which automatically cancels the magnetic field to the back lobes by replacing the traditional circular coils with a three-dimensional (3D) coil scheme inspired by a generalized form of Halbach arrays. It is shown that, along with the miniaturization of the transmitter system, it allows for improved magnetic field intensity in the target side. Measurement of the produced magnetic patterns verifies that the power transfer to the back lobe is 15-fold smaller compared to the corresponding distance on the main lobe side, whilst maintaining a powering efficiency similar to that of conventional planar coils. To show the application of the proposed array, a wireless charging pad with an effective powering area of 144 cm2 is fabricated on 3D-assembled printed circuit boards. This 3D structure obviates the need for traditional magnetic shield materials that place limitations on the working frequency and suffer from non-linearity and hysteresis effects.

Selective Manipulation and Trapping of Magnetically Barcoded Materials

“…To encode the magnetic chains into the hydrogel, a main array of magnets with a set of nonrepeating codes was designed. Although Neodymium magnets usually produce strong magnetic fields, to reach more intense magnetic fields intensity in the gelation zone, two auxiliary sets of side magnets were added to the design, which are inspired from the Halbach array [19,45] . The axillary magnets are oriented such that they constructively interfere with the main array's field at top of the magnetic encoders where the gelation occurs.…”

“…This magnetic barcoded tag must satisfy a series of conditions to interact strongly with an external stimulus. By engineering the external stimulus with arrays of permanent magnets or coils, [15,16,19,20] we are able to selectively manipulate such encoded tags from background magnetic materials via the enhanced interactions that occur with matching codes.…”

Hybrid Coils-Based Wireless Power Transfer for Intelligent Sensors

“…Other studies have used the WPT technique at different frequencies to optimize transfer efficiency while studying side effects on skin for implantable medical devices [5]. WPT has been used in magnetic resonance imaging coils for improved magnetic field intensity on the patient side [6].…”

Editorial for the Special Issue on Implantable Microdevices

“…There are eight research articles and one review article published in this special issue, covering a wide range of topics: implantable sensors for detecting biophysiological and biophysical signals [1,2]; novel transducers for stimulation [3]; miniaturized antennas and biotelemetries for wireless implants [4,5,6] medical electronics and system-on-chip (SoC) [1,7]; and nano/microfabrication technologies for implantable microdevices [2,8,9]. On the device side, Chen et al reported a tongue pressure sensing platform that integrated interdigitated pressure sensing electrodes with SoC on flexible polymer films.…”

“…This special issue includes multiple designs of wireless antennas that have been explored by different groups. In particular, Hajiaghajani et al proposed a three-dimensional coil array based on a generalized Halbach array for wireless powering of biomedical instruments within a large area of 144 cm 2 while eliminating the need for traditional magnetic shielding [4]. In another design, Fan et al designed a miniaturized circularly polarized antenna for in-body wireless communication with broadened bandwidth [5].…”