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.
Highlights
Wireless power transfer (WPT) plays a key role in developing instruments that rely on external powering such as electric vehicles [1], micro-devices [2], and biomedical implants [3,4]
Planar coils printed on circuit boards have been the major building block of most of wireless power transfer systems for many years
A new type of power transmitter coil has been developed by employing 3D current routes instead of planar printed coils
Summary
Wireless power transfer (WPT) plays a key role in developing instruments that rely on external powering such as electric vehicles [1], micro-devices [2], and biomedical implants [3,4]. Wireless powering structures were based on the resonant coupling of aligned coils [5] and geometry optimization of the power transmitter (Tx) and receiver (Rx) coils [6]. Such structures generate intense magnetic fields over the surrounding space and are able to cause electromagnetic (EM) interference with nearby electric equipment [7,8]. ((aa)) AA ttyyppiiccaall lliinneeaarr HHaallbbaacchh aarrrraayy iinn wwhhiicchh tthhee mmaaggnneettiizzaattiioonn vveeccttooorrrsssaarree nnootteedd aanndd ((bb)) iittss ccooiill--bbaasseeddeeqquuiivvaalleenntt. TThhee eennttiirree aarrrraayy sscchheemmee wwaass mmooddeelleedd uussiinngg tthhee ssooffttwwaarree CCOOMMSSOOLL aanndd tthhee rreessuullttaanntt ssppaattiiaall ppaatttteerrnn ooff mmaaggnneettiicc ffiieellddssoonn aa ttyyppiiccaall yy--ppllaannee iiss sshhoowwnn iinn FFiigguurree44bb. Bmyapglnaectiincgfitehled’ascitnutaetnosritbyetswigeneinfictahnetblyoddyecarneadstehse, wpihcikcuhplecaodilsstoofmthine iMmRizIi,nigt wthaesionbtesrefrevreednctehaint tthhee mimaaggnientgiccfoiiellsd. ’Isniandtednitsiiotyn,ssiignnciefitchaenxtlyanddecyrceoamseps,onwehnitcsholfetahdesmtoagmnientiicmfiizelidnsg gtheneeirnatteerdfebryenthcee ilantethrael icmoialgsicnagnccoelilos.uItneaadchdiotitohne,rsiinnctehethme axiannldobyecso, mthpeocnroesnstspooflathriezmatiaognniestiicnfsiieglndisfigceannet.rated by the lateral coils cancel out each other in the main lobes, the cross polarization is insignificant
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