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Shengbin Li, Yuanzhao Wu, Waqas Asghar, Fali Li, Ye Zhang, Zidong He, Jinyun Liu, Yuwei Wang, [Meiyong Liao](https://orcid.org/0000-0003-1361-4266), Jie Shang, Long Ren, Yi Du, [Denys Makarov](https://orcid.org/0000-0002-7177-4308), Yiwei Liu, [Run‐Wei Li](https://orcid.org/0000-0003-3879-9834)

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[Wearable Magnetic Field Sensor with Low Detection Limit and Wide Operation Range for Electronic Skin Applications](https://mdr.nims.go.jp/datasets/ab86f38c-6e67-4654-b436-aa48d56523b3)

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Wearable Magnetic Field Sensor with Low Detection Limit and Wide Operation Range for Electronic Skin ApplicationsRESEARCH ARTICLEwww.advancedscience.comWearable Magnetic Field Sensor with Low Detection Limitand Wide Operation Range for Electronic Skin ApplicationsShengbin Li, Yuanzhao Wu,* Waqas Asghar, Fali Li, Ye Zhang, Zidong He, Jinyun Liu,Yuwei Wang, Meiyong Liao, Jie Shang, Long Ren, Yi Du, Denys Makarov,* Yiwei Liu,*and Run-Wei Li*Flexible electronic devices extended abilities of humans to perceive theirenvironment conveniently and comfortably. Among them, flexible magneticfield sensors are crucial to detect changes in the external magnetic field.State-of-the-art flexible magnetoelectronics do not exhibit low detection limitand large working range simultaneously, which limits their applicationpotential. Herein, a flexible magnetic field sensor possessing a low detectionlimit of 22 nT and wide sensing range from 22 nT up to 400 mT is reported.With the detection range of seven orders of magnitude in magnetic fieldsensor constitutes at least one order of magnitude improvement over currentflexible magnetic field sensor technologies. The sensor is designed as acantilever beam structure accommodating a flexible permanent magneticcomposite and an amorphous magnetic wire enabling sensitivity to lowmagnetic fields. To detect high fields, the anisotropy of the giantmagnetoimpedance effect of amorphous magnetic wires to the magnetic fielddirection is explored. Benefiting from mechanical flexibility of sensor and itsbroad detection range, its application potential for smart wearables targetinggeomagnetic navigation, touchless interactivity, rehabilitation appliances, andsafety interfaces providing warnings of exposure to high magnetic fields areexplored.1. IntroductionBenefiting from their mechanical flexibility, flexible electronicscan be used as components of smart wearables or conformallyS. Li, Y. Wu, W. Asghar, F. Li, Y. Zhang, Z. He, J. Liu, Y. Wang, J. Shang,Y. Liu, R.-W. LiCAS Key Laboratory of Magnetic Materials and DevicesNingbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201, P. R. ChinaE-mail: wuyz@nimte.ac.cn; liuyw@nimte.ac.cn; runweili@nimte.ac.cnThe ORCID identification number(s) for the author(s) of this articlecan be found under https://doi.org/10.1002/advs.202304525© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.This is an open access article under the terms of the Creative CommonsAttribution License, which permits use, distribution and reproduction inany medium, provided the original work is properly cited.DOI: 10.1002/advs.202304525applied to human skin.[1–4] Human skinprovides the valuable information on thesurrounding environment such as temper-ature and pressure, which help us to per-ceive the world.[2] Modern electronic skin(E-skin) devices expand the abilities of ourskin prescribed by nature by providing ad-ditional perception abilities like sound,[5]optics,[6] and direction.[7] Among them,magnetosensitive E-skins enable novel typeof artificial receptors[8] for sensing mag-netic fields for navigation or realizing inter-active human-machine interfaces in virtualand augmented reality.[9,10] With the help ofmagnetosensitive E-skins, we can perceivenot only static but also dynamic magneticfields.[11–13]Typical magnetic fields surrounding usin our everyday life range from sub-nT(biomagnetic fields) up to about T (fieldof strong permanent magnets or magneticresonance imaging (MRI) devices). Mag-netic field sensors can detect tiny mag-netic fields for interactive electronics basedon geomagnetic field[7,14,15] as well as bio-/medical applications including magneticlabeling upon cell monitoring,[16] biological single magnetic beaddetection,[17] and multiplex protein detection.[18] Strong mag-netic fields can also affect the function of the brain and heart,creating potential health risks,[19,20] especially for patients usingS. Li, Y. Wu, W. Asghar, F. Li, Y. Zhang, Z. He, J. Liu, Y. Wang, J. Shang,Y. Liu, R.-W. LiZhejiang Province Key Laboratory of Magnetic Materials and ApplicationTechnologyNingbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201, P. R. ChinaS. Li, R.-W. LiSchool of Future TechnologyUniversity of Chinese Academy of SciencesBeijing 100049, P. R. ChinaW. AsgharMechanical Engineering DepartmentUniversity of Engineering and Technology TaxilaTaxila 47050, PakistanAdv. Sci. 2024, 11, 2304525 © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH2304525 (1 of 11)http://www.advancedscience.commailto:wuyz@nimte.ac.cnmailto:liuyw@nimte.ac.cnmailto:runweili@nimte.ac.cnhttps://doi.org/10.1002/advs.202304525http://creativecommons.org/licenses/by/4.0/http://creativecommons.org/licenses/by/4.0/http://crossmark.crossref.org/dialog/?doi=10.1002%2Fadvs.202304525&domain=pdf&date_stamp=2023-11-30www.advancedsciencenews.com www.advancedscience.comelectronic devices such as pacemakers.[21] Thus, in addition tomonitoring small magnetic fields for medical and interactive ap-pliances, the detection and early warning of strong magneticfields is essential for human safety and security.Contemporary wearable magnetic field sensors are designedto detect magnetic fields in specific ranges, which does not allowcovering envisioned application scenarios ranging from healthmonitoring (detection of low fields of nT range) to safety (de-tection of high fields in the range of Tesla). Flexible magneticfield sensors rely on various sensing principles including mag-netoresistive, magnetoimpedance, and Hall effects. Ever sincethe pioneering work of S. S. P. Parkin, who revolutionized thefield by crafting exchange-biased magnetic sandwiches on self-supporting organic films, ushering in the era of flexible gi-ant magnetoresistive (GMR) sensors with the remarkable abil-ity to detect magnetic fields up to 4mT, this domain has at-tracted considerable attention.[22] D. Makarov et al. successfullydevised [Py/CoFe]/Cu/[CoFe/Py]/IrMn heterostructures on poly-imide foils as substrates, thereby enabling magnetic field moni-toring within the wide range of 2–40 mT.[23] Our research teamcontributed by designing flexible dual spin valves on pre-strainedpolydimethylsiloxane (PDMS) substrates, attaining a maximummagnetic field detection capability of 90 mT.[24] A. Fert and hiscolleagues harnessed Co/Al2O3/Co thin films prepared on theremarkable Flexible Gel-film platform to fabricate magnetic sen-sors based on the tunnel magnetoresistance (TMR) effect, capa-ble of detecting magnetic fields up to 10 mT.[25] Moreover, mag-netic field-sensitive electronic skins often employ sensors basedon the anisotropic magnetoresistance (AMR) effect, owing totheir intrinsic anisotropy. Notably, D. Makarov et al. successfullymanufactured permalloy (Py) films and Py/Ta powder on PETand mylar substrates, respectively, attaining impressive magneticfield detection ranges of 0.2 μT–0.05 mT[26] and 60 μT–400 mT.[27]Sensors utilizing the magnetically driven stress effect often relyon the deformation of magnetic particles under a magnetic fieldto alter the material’s electrical properties, X. Gong et al. inge-niously integrated Carbonyl-iron μPs into PDMS, thereby achiev-ing a remarkable maximum magnetic field detection capability ofF. Li, Z. He, J. Liu, R.-W. LiCenter of Materials Science and Optoelectronics EngineeringUniversity of Chinese Academy of SciencesBeijing 100049, P. R. ChinaM. LiaoNational Institute for Materials ScienceTsukuba, Ibaraki 305-0044, JapanL. RenState Key Laboratory of Advanced Technology for Materials Synthesis andProcessing International School of Materials Science and EngineeringWuhan University of TechnologyWuhan 430070, P. R. ChinaY. DuSchool of PhysicsBeihang UniversityBeijing 100191, P. R. ChinaD. MakarovInstitute of Ion Beam Physics and Materials ResearchHelmholtz-Zentrum Dresden-Rossendorf e.V.Bautzner Landstrasse 400, 01328 Dresden, GermanyE-mail: d.makarov@hzdr.de150 mT.[28] Similarly, D. Zhu et al. seamlessly integrated AgNWs-Fe3O4-PDMS and flexible organic transistors on polyimide foils,culminating in magnetic field detection ranging from 0.5 mTto 150 mT.[29] Furthermore, certain materials, such as Bi, boast-ing non-saturating large magnetoresistance, have the potential toprofoundly enhance magnetic field detection. In a notable feat, D.Makarov et al. successfully fabricated Bismuth on polyimide foils,resulting in a magnetic field detection range spanning from 14 μTto 500 mT.[30] Exploiting the Hall effect for magnetic field detec-tion, D. Neumaier achieved an impressive maximum detectioncapability of 18 mT.[31] Cobalt-based amorphous wires may ex-hibit near-zero magnetostriction, a feature that’s beneficial in ap-plications where changes in magnetic properties due to mechan-ical stress are undesirable. These wires are extensively utilizedin magnetic field sensors, including giant magnetoimpedance(GMI) and fluxgate sensors. They serve as cores in many types ofthese sensors, especially in orthogonal fluxgates, contributing tothe sensor’s performance by facilitating certain magnetic prop-erties. Co-based amorphous alloys, from which these wires aremade, exhibit good magnetic permeability and low remagnetiza-tion loss. These traits are advantageous in applications requiringefficient magnetic performance. Co-based amorphous wires arenoted for their flexibility, which could be beneficial in applica-tions where the material’s formability and ductility are important.Although it still has limitations such as high cost and poor repro-ducibility as a sensitive material for magnetic sensors. Comparedwith other materials, it has much higher sensitivity and softnessthan other sensors, making Co-based amorphous wire an idealmaterial for preparing flexible magnetic sensors. Xiao et al. usedamorphous wire to design a multimodal sensor that can detectmagnetic fields as low as 50μT while being able to stretch by morethan 30%.[32] The fluxgate sensor based on Co-based amorphouswire designed by Yang et al. can achieve magnetic field measure-ments as low as 0.1 nT.[33] Compared with other materials, it hasmuch higher sensitivity and softness than other sensors, makingCo-based amorphous wire an ideal material for preparing flexiblemagnetic sensors.This survey of the recent reports on flexible magnetic fieldsensors reveals that it is difficult to realize low detection limitsand wide operation range in a single sensing element.[34–36] Wenote that this is not the issue specific to flexible magnetoelec-tronics. The same problem is discussed also for well-establishedrigid magnetic field sensors. To achieve a wide range of mag-netic field measurements, a typical approach is to integrate a vari-ety of magnetic field sensors in a single device.[37] However, thisapproach requires more complex signal conditioning circuits,which increases the complexity of the sensor system design.Therefore, realizing a single sensing unit revealing high me-chanical flexibility, low detection limit, and wide operation rangeremains an unsolved problem of current magnetic field sensortechnologies.Herein, we report a flexible magnetic field sensor having awide sensing range from 22 nT to 400 mT and low detectionlimit of 22 nT. Our sensing unit includes an amorphous Co-basedmicrowire revealing GMI effect, which enables detection of lowmagnetic fields of 22 nT while providing mechanical flexibility.The GMI wire alone is magnetically saturated in a magnetic fieldof less than 50 mT. To sense higher magnetic fields, we designeda cantilever beam structure consisting of a flexible permanentAdv. Sci. 2024, 11, 2304525 © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH2304525 (2 of 11) 21983844, 2024, 37, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/advs.202304525 by National Institute For, Wiley Online Library on [09/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advancedscience.commailto:d.makarov@hzdr.dewww.advancedsciencenews.com www.advancedscience.commagnet patch and a GMI wire. In this system, the cantilever beamis bent when exposed to an external magnetic field. The change ofthe angle between the amorphous wire and the magnetic field re-sults in a continuous change of the impedance of the amorphouswire providing the possibility to also measure stronger magneticfields of up to 400 mT maintaining a low limit of detection downto 22 nT. By harnessing this novel cantilever beam structural de-sign, we efficaciously augment the detection ambit of sensorsanchored on amorphous wires, renowned for their pronouncedsensitivity. This innovation ensures their adaptability across bothminuscule and pronounced magnetic field contexts. The sensoris mechanically flexible and compact and operates not only whenworn on skin but also in a constrained environment being inte-grated in a decorative fingernail. These smart magnetosensitivewearables can help us perceiving the actual magnetic fields sur-rounding us in our daily activities. We demonstrated the appli-cation potential of our wearable magnetic field sensors for geo-magnetic navigation, realization of interactive human-machineinterfaces for entertainment and rehabilitation purposes as wellas safety warning systems in case exposure to strong magneticfields.2. Results and Discussions2.1. Concept of Wearable Magnetic Field SensorTaking into account that interactivity is typically realized by point-ing with our pointing finger on the object of interest or touchingthe screen of a smartphone, it is instructive to apply flexible mag-netic field sensors to the finger (Figure 1a). Figure 1b shows themeasurement principle of the sensor.When the magnetic field is small (not sufficient to bend thecantilever beam, accommodating the GMI wire, to the field di-rection), the sensing mechanism is based on the GMI effect ofthe magnetic amorphous wire. The interaction force between themagnetic field and the magnet block is very small and can beignored. At this time, the shape of the cantilever beam itself re-mains unchanged. When the magnetic field increases, the amor-phous magnetic wire becomes magnetically saturated. However,the interaction force between the magnetic field and the magnetblock increases to the point where it is difficult to ignore. Underthe influence of the magnetic force, the cantilever beam bends inthe direction of the magnetic field. The angle between the amor-phous wire and the magnetic field changes accordingly, causingthe sensor saturation impedance to change (Figure S1, Support-ing Information). Thus, we can rely on the bending of the can-tilever beam in the field direction to achieve larger magnetic fielddetection.In this case, the impedance of the amorphous wire may changedue to the magnetic field (magnetoimpedance effect) and thestress (stress impedance effect). Both of these effects originatein the change of the magnetic domain pattern driven by an exter-nal stimulus. We confirm experimentally (Figure S2, SupportingInformation) that when the amorphous wire is in a magneticallysaturated state, the applied stress hardly affects its impedance.This can be understood based on the consideration that for thinamorphous wires, mechanical bending does not produce sizablestress. Therefore, if the amorphous wire is saturated in a highmagnetic field, the sensing mechanism is mainly based on theanisotropy of the sensitivity of the amorphous wire to the direc-tion of the applied magnetic field[38,39] (Figure S2, Supporting In-formation). For the Co-based wire used in our work, there is adistinct difference in the magnetoimpedance (MI) response ofthe sensor to magnetic fields applied along (13 Ω) or perpendic-ular (15 Ω) to the wire (the impedance change differs by 8% withrespect to the nominal impedance of 25 Ω).2.2. Preparation of Flexible Magnetic SensorThe fabrication process of the sensor is shown in Figure 1c,which includes the fabrication of a mechanically flexible can-tilever beam structure accommodating Co-based amorphouswire and a flexible permanent magnet. The elasticity of the can-tilever allows it to undergo small displacements when a force isapplied. This displacement can be detected by electronic devicesand converted into electrical signals, enabling sensitive detectionof external stimuli.[40] This conversion is so sensitive that evenvery small mechanical displacements can be detected and con-verted into readable electrical signals.The mechanical stability is given by the flexibility of the amor-phous magnetic wire connected using a liquid metal intercon-nect with excellent tensile properties. Co wire and liquid metalinterconnects are encapsulated in a cantilever structure made ofpolyimide. A flexible permanent magnet is based on hard mag-netic particles (NdFeB, 9 wt%) dispersed in an elastomer matrix(PDMS) and is placed on one end of the cantilever structure. Thesensor structure is encapsulated with PDMS to assure mechani-cal integrity and biocompatibility.Compared to manually fabricated methods, 3D electronicprinting technologies, such as inkjet or aerosol jet printing,[41–43]undeniably enhance the repeatability and reliability of sen-sors. Nevertheless, when it comes to complex structures in-cluding sensitive materials, encapsulation materials, and con-ductive pathways, direct 3D printing exist numerous chal-lenges. So, we currently use manual fabricating to prepare oursensors.The sensor of the final cantilever structure is shown inFigure 1d. Amorphous wire and liquid metal interconnects aredistributed on both sides of the cantilever beam (Figure 1e). Inthe initial state, the sensor cantilever is curved, as shown inFigure 1f. The entire sensing unit is compact and can be seam-lessly integrated even in a decorative fingernail capable of real-time detection of magnetic fields in a wide range. At the sametime, it has good flexibility and can withstand bending in differ-ent directions (Figure 1g,h) as it is relevant for smart skin andsmart textile applications of this technology.2.3. Structure and Performance Characterization of the MagneticField SensorWe characterized amorphous Co-based wires of different diame-ters (Figures S4 and S5, Supporting Information). The morphol-ogy of the amorphous wires was observed by scanning electronmicroscope (SEM) and energy dispersive spectrometer (EDS), asshown in Figure S3 (Supporting Information). The wire has asmooth glass fiber package. Wires are mainly composed of Cr,Adv. Sci. 2024, 11, 2304525 © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH2304525 (3 of 11) 21983844, 2024, 37, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/advs.202304525 by National Institute For, Wiley Online Library on [09/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advancedscience.comwww.advancedsciencenews.com www.advancedscience.comFigure 1. Flexible amorphous wire-based magnetic field sensor for wide-range magnetic field measurements and low detection limit. a) Schematicdiagram of magnetic field detection. The sensor can be applied to or integrated in a decorative fingernail. The sensor is in the form of a cantilever beamand can detect magnetic field of different strength. b) Detection principle of the flexible magnetic field sensor. When the magnetic field is small, thecantilever beam retains its bent state. The magnetic field is measured based on the GMI effect of the amorphous wire itself. When the magnetic fieldbecame stronger, due to the interaction between the magnetic field and the magnetic patch, the cantilever beam and the amorphous wire are bent in theparallel direction to the magnetic field. Thus, the response curve of the amorphous wire to the magnetic field and the impedance of the sensor changes.c) The preparation process of the sensor: an elastic permanent magnet patch is formed by mixing NdFeB and PDMS. The patch is magnetized in apulsed magnetic field and placed on a cantilever beam accommodating a GMI wire-based sensor. Conductive lines are formed by brushing liquid metalat appropriate places for contacting the sensors. The entire device is encapsulated in PDMS. d) Optical image of the sensor and e) a close-up of theamorphous wire and liquid metal contacts. f) The sensor is applied to a decorative nail. g,h) Bendability of the sensor devices.Fe, and Co. The magnetic hysteresis loop of a Co-based amor-phous wire was measured by applying a magnetic field along thewire in a vibrating sample magnetometer (VSM). The hystere-sis loop is almost closed, which is characteristic of a soft mag-netic material (Figure S5, Supporting Information). The satura-tion magnetic field is about 2.5 mT. The magnetic permeabil-ity of the sensor decreases with the increase of the driving fre-quency of the magnetic field and then remains almost unchangedafter 500 Hz. Here, 30 μm wire has the highest magnetic per-meability. The GMI effect in amorphous wires has been associ-ated with a rapid change in the skin depth, driven by the low-field sensitivity of the azimuthal dynamic permeability. Thus, theAdv. Sci. 2024, 11, 2304525 © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH2304525 (4 of 11) 21983844, 2024, 37, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/advs.202304525 by National Institute For, Wiley Online Library on [09/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advancedscience.comwww.advancedsciencenews.com www.advancedscience.comamorphous wire with larger magnetic permeability has betterGMI performance,[32] and the 30 μm amorphous wire has thebest performance, so we chose an amorphous wire of this size.Furthermore, we characterized the impedance change of theamorphous wire under magnetic fields of different driving fre-quencies and currents. From Figure S6 (Supporting Informa-tion), it can be found that as the driving frequency increases(0.5 kHz–5 MHz), the MI effect of the amorphous wire under1 mA driving current increases from nearly 0% to a maximum of58%. The effect of driving current can be explained by consider-ing the tensor character of magnetic permeability. The differentdependences of GMI on driving alternating current can also beattributed to the difference in the domain structures of the inves-tigated samples. At low-amplitude currents, there’s an inhomo-geneous distribution of local critical magnetic fields, causing the“spike” feature in GMI profiles or the instability of the GMI sig-nal. As the current increases, a corresponding magnetic field willbe generated inside the amorphous wire, thereby magnetizing it,and making the local magnetic field evenly distributed. Perviouswork also shows, under certain range of the currents, increasingthe amplitude can greatly improve the GMI signal.[44]When the amorphous wire is bent, its impedance will decreaseaccordingly. This is because the amorphous wire is affected bystress during the bending process. The giant stress impedanceeffect of amorphous wire will cause it to reduce its impedance un-der the action of stress (Figure S2, Supporting Information). Wetested the change of amorphous wire impedance with a magneticfield under different bending conditions (Figure S7, Support-ing Information). It can be seen that the maximum impedancechange rate of the sensor decreases as the angle decreases. Thereason for this phenomenon is that on the one hand, the de-crease in the initial impedance reduces the change rate, and onthe other hand, the bending of the amorphous wire also causesthe magnetic field to decrease the axial component of the amor-phous wire.Then we investigated the impedance change of the amorphouswire under magnetic fields of different driving currents and fre-quencies. The change of the driving current will affect the initialradial magnetization of the amorphous wire, thus affecting thechange of its impedance with the external magnetic field. There-fore, we explored the MI effect of the amorphous wire under thedriving current varying from 0.1 to 40 mA (Figure S8, Support-ing Information) with the 5 MHz driving frequency. With the in-crease of the driving current, the MI response first increases andthen decreases revealing a maximum of 40% at 1 mA.However, when the amorphous wire is integrated into thesensor structure with liquid metal interconnects, it exhibits adifferent frequency response compared to an individual amor-phous wire. The MI response of the integrated sensor with poly-imide substrate first increases and then decreases with frequency(Figure 2a) with its maximum of 28% at 3 MHz while under the1 mA driving current. We anticipate that the reason for this obser-vation is related to the change of the skin effect of the connectingline, which is used to connect the sensor (Cu and liquid metal).At higher frequencies, the skin effect becomes more pronouncedresulting in a higher impedance of the sensor and its weaker sen-sitivity to the applied magnetic field.Similarly, the choice of the sensor substrate will affect themechanical performance of the sensor under stress, thereby af-fecting the sensor’s ability to detect large magnetic fields. Tothis end, we tested various polymer materials with differentmechanical properties (polyimide (PI), polycarbonate (PC), andpolyurethane (PU)) to prepare sensing devices and characterizedthe sensor response curves when exposed to magnetic fields.First, we obtain the stress-strain curve of the material, therebycalculating the elastic modulus (Figure S7, Supporting Informa-tion). Among them, polyimide material has the highest Young’smodulus (1.3 GPa). When it was used as a substrate for the wire-based sensor, as shown in Figure 2b, the sensor revealed the high-est MI response of 27% with the 3 MHz driving frequency and1 mA driving current. Still, sensors prepared on other substratesalso have excellent magnetic detection ability with the MI effectof 24–25%. Hence, relying on our technology, we can select thesubstrate with respect to its mechanical properties to match therequirement of the selected application scenario. In the follow-ing, we discuss sensors prepared on polyimide as it provides thelargest operation range for our sensor.We explored the response of cantilevers of different lengths(1–5 cm) to magnetic fields (Figure 2c). The MI effect increasesfrom 20% to 35% as the length of the cantilever increases withthe 3 MHz driving frequency and 1 mA driving current. Thisis because the shorter cantilever beam makes the amorphouswire closer to the magnet patch, thus having a smaller initialimpedance (the magnetic field of the magnet patch itself willreduce the impedance of the amorphous wire), resulting in asmaller impedance change. Considering that wearable devices re-quire a smaller size, we used a 3 cm-long cantilever beam struc-ture in subsequent experiments.Further, we characterize the hysteresis loops of the flexiblemagnet patch with different PDMS and NdFeB composition(Figure S10, Supporting Information). As the content of NdFeBin the composite decreases from 33 wt% to 9 wt%, the saturationmagnetization of the magnet decreases from 35.5 to 8.7 emu g−1.The magnetic moment of the magnet patch at the free end ofthe cantilever beam will affect its interaction force with the exter-nal magnetic field. In this way, the operation range of the sen-sor at higher fields will be affected. In particular, reduction ofthe saturation magnetization of the composite makes the sensormore difficult to deform and increases the sensor’s measurementrange (Figure 2d). For instance, having a PDMS:NdFeB compos-ite with a 10:1 weight ratio (9% wt NdFeB), the sensor is capableof achieving magnetic field detection up to about 450 mT, whilethe sensor having PDMS:NdFeB composite with a 2:1 weight ra-tio (33% wt NdFeB) can only detect the magnetic field of about200 mT.The position of the magnet on the cantilever beam also affectsthe operation range of the sensor. We placed small patches ofthe flexible magnet at the top (3 cm to the tail of the cantilever),center (1.5 cm to the tail of the cantilever), and tail of thepolyimide cantilever beam, and assessed the corresponding MIperformance of the sensor with 3 MHz driving frequency and1 mA driving current(Figure 2e). As the position of the flexiblemagnet approaches the top of the cantilever beam, the MI effectincreases from 22% to 28%. This enhancement can be explainedconsidering that the position of the magnet patch affects thetorque of the magnetic field and its interaction force, therebychanging the effect of the magnetic force and affecting thedetection range of the sensor. We built the following model toAdv. Sci. 2024, 11, 2304525 © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH2304525 (5 of 11) 21983844, 2024, 37, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/advs.202304525 by National Institute For, Wiley Online Library on [09/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advancedscience.comwww.advancedsciencenews.com www.advancedscience.comFigure 2. Characterization of the flexible magnetic field sensor. a) Response of the flexible magnetic field sensor to the magnetic field. The sensor isdriven at different frequencies with PI substrate. The driving current is 1 mA. b) Response of the flexible magnetic field sensor to the magnetic field whenthe sensor is fabricated on different substrate material, with 3 MHz driving frequency and 1 mA driving current. c) Magnetic field response of sensorswith prepared on cantilever beams of different length made of polyimide material. d) The maximum field, which can be detected with our sensor, whenusing magnetic patches with different concentration of magnetic particles. The insert shows the magnetic remanence of the composites with differentcontent of magnetic particles. As the PDMS content increases, the remanence magnetization (Mr) of the magnet patch decreases, while the maximumfield, which can be detected by the sensor, increases. e) MI performance of the sensor dependent on the position of the magnet patch, which is locatedat different positions on the cantilever beam.explain this phenomenon: Since the initial bend of the cantileverbeam is 45°, the direction of B relative to the magnet’s momentchanges along the length of the beam.The torque 𝜏 on the magnet due to the magnetic field is givenby:𝜏 = m × B (1)where the magnitude is given by:𝜏 = mBsin (𝜃) (2)where 𝜃 is the angle between m and B.As the location of the magnet is changed from the base towardthe free end of the cantilever, the angle 𝜃 between the magneticmoment m and B increases from 45° to 90°.Since sin(45◦) =√2 ∕2 and sin(90◦) = 1, the torque 𝜏 on themagnet due to B will increase as the magnet is moved towardthe free end. This means the moment exerted on the cantileverbeam will also increase as the magnet is moved toward the freeend.The moment at the free end will be maximum because therethe angle 𝜃 is maximum, that is, 90°. And the moment at the fixedend will be minimum because there the angle 𝜃 is minimum, thatis, 45°.In summary, the moment on the cantilever beam due to themagnet’s interaction with the magnetic field will increase asthe magnet is moved from the fixed end to the free end of thecantilever. The larger moment makes our cantilever beam re-turn to the parallel state faster, which reduces the range of thesensor.Adv. Sci. 2024, 11, 2304525 © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH2304525 (6 of 11) 21983844, 2024, 37, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/advs.202304525 by National Institute For, Wiley Online Library on [09/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advancedscience.comwww.advancedsciencenews.com www.advancedscience.comFigure 3. Response of the flexible magnetic field sensor to the magnetic field of different strength. a) MI response of the sensor in the range of 0 – 600mT. Insert is an enlarged view of the sensor response at 0-0.1 mT and 100–600 mT. b) MI performance of the sensor (right y-axis) exposed to magneticfield, which increases 22 nT every 10 s (left y-axis). c) MI performance of the sensor (right y-axis) exposed to magnetic field, which increases 100 mTevery 10 s (left y-axis). d) Stability of the MI performance of the sensor exposed to 100 cycles of an applied magnetic field of 200 mT. The sensor is madeof PI substrate, with a measurement frequency of 3 MHz, a current of 1 mA, a cantilever beam length of 3 cm, and a magnet at the top.2.4. Magnetic Field Detection Performance of the FlexibleMagnetic Field SensorIn Figure 3a, we demonstrate that our sensor can respond to mag-netic fields over a wide range (0–600 mT). Using Helmholtz coilssetup, we increased the magnetic field by 22 nT increment every10 s. We demonstrate that for each strength of the magnetic field,the MI effect of the sensor increases by about 0.1%. This demon-strates that we can detect small magnetic fields as low as 22 nTwith our flexible sensor (Figure 3b), and the GF value can reachup to 400. At the same time, when the magnetic field increases,the deflection of the cantilever changes the angle between theamorphous wire and the magnetic field so that the sensor candetect the magnetic field exceeding its saturation magnetic field.We measured the change of the sensor impedance by increas-ing the magnetic field with an increment of 100 mT every 10 s(Figure 3c). It can be seen that the impedance change rate of thesensor after 200 mT is about 0.01%/100 mT, and the GF valuecan reach ≈0.04. Thus, our sensor has a measurable response tomagnetic field range in a wide range (22 nT–400 mT). We furthermeasured the sensor’s response to the magnetic field at 0–30 nT.From Figure S11 (Supporting Information), we believe that thesensor can resolve a magnetic field of about 2 nT.We then studied the response of the sensor under differentmagnetic fields. Due to the anisotropy of the amorphous wireto the horizontal magnetic field and the vertical magnetic field(Figure S2, Supporting Information), the sensor respondsdifferently to magnetic fields at different angles. The sensorAdv. Sci. 2024, 11, 2304525 © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH2304525 (7 of 11) 21983844, 2024, 37, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/advs.202304525 by National Institute For, Wiley Online Library on [09/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advancedscience.comwww.advancedsciencenews.com www.advancedscience.comwill undergo obvious periodic changes during rotation in themagnetic field, which also shows that our sensor can sense theangular changes of the magnetic field (Figure S12, SupportingInformation).In Figure 3d, we explore the long-term stability of the sensor.We use an electromagnet to cycle a 200 mT magnetic field 1000times and measure the sample impedance upon cycling. As thenumber of cycles increases, the MI effect of the sensor remainsat the level of 28% without any notable degradation. Therefore,our sensor not only has excellent magnetic detection ability butalso has stable repetitive detection ability.Response time is also an important parameter of the sensor.Here we characterize the response time of the sensor after ap-plying a 22nT magnetic field. The response time only takes 0.03s (Figure S13, Supporting Information), which can quickly re-spond to changes in the magnetic field. We then prepared threeidentical sensors using the same manufacturing method andcharacterized their initial impedance and saturated impedancechange rate. As shown in Figure S14 (Supporting Information),although the manual process limits the uniformity of the sensor,its impedance change rate and resistivity change little, shows thatthe sensor has good repeatability.Compared with different types of previously reported flexiblemagnetic field sensors (Table S1, Supporting Information), oursensor has the lowest detection limit (much lower than other sen-sors) and can achieve magnetic field detection spanning 7 ordersof magnitude while having the lowest detection limit. and thewidest detection range.2.5. Applications of Flexible Magnetic Field SensorsWe applied our sensor to the finger (Figure 4a,c) or integratedin a decorative nail (Figure 4e) to demonstrate its application indaily life. This smart wearable can help us perceiving the mag-netic field of the environment in real-time, for instance to realizegeomagnetic navigation (Figure 4a, Video S1, Supporting Infor-mation). When we move the finger decorated with the sensor,the angle between the amorphous wire and the geomagnetic fieldchanges, thus changing the impedance of the sensor 2.7% at themaximum (Figure 4b). In the process of finger movement, wemeasure the impedance of the sensor in real-time and input it tocomputer realizing human-machine interface for touchless in-teractivity. In this way, we exemplarily show the realization of thevirtual reality interface for real-time precise control of the driv-ing direction of a car in a computer game (about 0.4° theoreti-cal accuracy, 0.5 Ω impedance variation per 180° with 0.001 Ωaccuracy of impedance analyzers). This demonstrator suggeststhat our sensor can be used also to interact with virtual displaysfor prospective augmented reality applications. This setup can beused for rehabilitation purposes to improve fine motoric functionof fingers after injuries or as an interface to train concentrationof participants.For example, we attach a small, flexible magnet to the arm ata spot where the pulse can cause a slight movement. This move-ment occurs because the pulse creates a rhythmical throbbing,which in turn, causes the magnet to move back and forth slightly.Sensors can detect this movement since it causes a change in themagnetic field surrounding them, specifically at the location ofthe sensor. Now, when a smart wearable device, equipped withthese sensors, is brought close to the area where the flexible mag-netic patch is attached, it can successfully monitor and track thehuman pulse (as illustrated in Figure 4c). Furthermore, Figure 4ddemonstrates how the sensor’s impedance (resistance to elec-trical flow) changes in response to the pulse. These changes inimpedance allow for the accurate identification of key peaks,labeled as P1, P2, and P3 peaks, within the pulse waveform.Through this setup, the wearable device can effectively captureand analyze the pulse, providing valuable data for health moni-toring or other applications.In Figure 4e, we demonstrate the application potential of thesmart magnetosensitive wearable for safety and security applica-tions. The increase of the sensor’s impedance when approachingto a source of strong magnetic field is shown in Figure 4f. For thisdemonstration, we used a piece of a strong permanent magnet.When the sensor is exposed to a magnetic field of certain strength(here, stronger than 200 mT), the system is programmed to senda warning signal, thus preventing exposure to strong magneticfields. This is crucial when the person should not be exposedto stronger magnetic fields for a long time as prescribed by theWorld Health Organization or for people using supporting med-ical equipment, for example, pacemakers. For the later, fields inthe range of 10 mT are already strong enough to influence thedevice.[45] Upon approaching an environment with high mag-netic fields like a MRI instrument or high-current carrying wiresin electrical vehicles or electromagnets (Video S2, Supporting In-formation), our wearable sensor can be used to warn the user fora potential danger.Although our sensor impedance measurement currentlyrequires connecting to an external measurement device(impedance analyzer), there are already some impedanceanalysis devices that can be carried around. At present, peoplehave integrated the AD5933 chip to realize an impedance anal-ysis instrument that can be carried daily.[46,47] It has frequencytesting capabilities from 5 Hz to 100 kHz and can measureimpedance from 10 Ω to 100 kΩ. Based on the rapid develop-ment of wearable electronic devices, it is expected to realizewearable high-precision impedance analysis equipment in thefuture.We emphasize that all demonstrations discussed above frommedical applications through interactive electronics up to thesafety systems were done with the same wearable sensing unit,which can detect small and large magnetic fields.3. ConclusionIn this work, we demonstrate a wearable magnetic field sensorwith a low detection limit of 22 nT and wide operation range from22 nT to 400 mT. Our sensor unit benefits from the giant mag-netoimpedance effect and anisotropy of the magnetoimpedanceresponse of the amorphous wire when exposed to a magneticfield of different orientation. When the magnetic field is small,we rely on the MI effect of amorphous wire to achieve high-precision magnetic field measurement. When the magnetic fieldbecomes larger, it will saturate the wire. Therefore, we use thecantilever beam structure to convert the change of the magneticfield into the interaction force between a patch of flexible mag-net and the magnetic field. This will drive the cantilever beam toAdv. Sci. 2024, 11, 2304525 © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH2304525 (8 of 11) 21983844, 2024, 37, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/advs.202304525 by National Institute For, Wiley Online Library on [09/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advancedscience.comwww.advancedsciencenews.com www.advancedscience.comFigure 4. Application scenarios of wearable magnetic field sensors. a) Gaming demonstration where a wearable sensor applied to a finger nail is usedto guide the direction of a car relying on the interaction with geomagnetic field (about 40 uT). The displacement of the car to the left or to the right iscontrolled by the swing of the hand (Video S1). The insert is an enlarged view of the sensor applied to the finger. b) The change of the impedance withthe swing of the finger, which is used to control the direction of the car in the game as shown in panel (a). c-d) The measurement of the pulse beatusing the sensor. A small flexible magnet patch is applied to the arm. The sensor on a finger is brought in proximity to the magnet patch, which allowsto measure the pulse caused by the change in the magnetic field due to the tiny displacement of the magnet. Typical magnetic field, which is detected bythe sensor in this demonstrator is 10 mT. e-f) Safety application demonstration. The same sensor as in previous examples can be used to detect strongmagnetic fields to warn the wearer on the undesired exposure. The magnetic field threshold for this particular demonstrator is set to 200 mT (Video S2).The sensor is made of PI substrate, with a measurement frequency of 3 MHz, a current of 1 mA, a cantilever beam length of 3 cm, and a magnet at thetop.bend, thereby changing the angle between the amorphous wireand the magnetic field. Using the anisotropy of its magnetic re-sponse, the sensor can continue measuring the magnetic fieldafter saturation. With this flexible magnetic field sensor technol-ogy, we can achieve a magnetic field measurement in the rangefrom 22 nT to 400 mT. Based on this design, our sensor can easilydetect various types of magnetic fields that appear in our every-day life. Due to the flexibility of the sensor, it can be easily appliedon skin or integrated in smart wearables even as a component ofa smart decorative nail. The sensor can detect the geomagneticfield so that it can be used in fields that require direction find-ing such as navigation and can also accurately measure the posi-tional relationship between the sensor and a flexible permanentmagnet. This can be used for rehabilitation purposes to improvefine motoric function of fingers after injuries or as an interface totrain concentration of participants. We used this wearable systemto accurately detect the magnetic field fluctuations of the smallpatch of flexible magnet on the arm during the rise and fall ofAdv. Sci. 2024, 11, 2304525 © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH2304525 (9 of 11) 21983844, 2024, 37, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/advs.202304525 by National Institute For, Wiley Online Library on [09/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advancedscience.comwww.advancedsciencenews.com www.advancedscience.comthe human pulse, resulting in the capturing of the pulse curve.At the same time, our sensor can also issue a warning when theexternal magnetic field is too large, reminding and protectingthe user, especially those users wearing magnetic field-sensitiveelectronic devices (such as cardiac pacemakers). Therefore, ourwork achieves low detection limits and wide-range magnetic fieldmeasurements in a single device, opening exciting prospects forthe application of wearable magnetic field sensing devices for in-teractive electronics, bioelectronics, safety, and security applica-tions.4. Experimental SectionPreparation of Liquid Metal: High-purity metals—Gallium, Indium,and Tin (99.99%, Beijing Founde Star Sci. & Technol. Co., Ltd) were amal-gamated in a mass ratio of 68.2:21.8:10. Subsequently, the mixture wassubjected to a thermal treatment at 60 °C for a duration of 30 min whilstbeing stirred, culminating in the formation of the LM Galinstan alloy(Ga68.2In21.8Sn10). Following this, the synthesized Galinstan was amal-gamated with micron-sized copper powder in a mass proportion of 9:1,whereupon the resultant blend underwent multiple cycles of heating andvacuum treatment to expunge air bubbles. The integration of copper pow-der with the liquid metal engendered a semi-liquid metal composite (Cu-EGaIn), thereby augmenting the wettability and adhesion characteristics.Preparation of Flexible Magnetic Field Sensors: The substrate of the sen-sor was prepared by dissolving polyimide powder (DuPont, USA) in chlo-roform. While for PC and PU substrates, its powder (DuPont, USA) wasprepared in acetone. The resulting mixture was placed in a glass moldfor 24 h to form a PI/PC/PU film with a thickness of 2 mm. The resul-tant mixture was placed in a glass mold for 24 h to form a film having athickness of 2 mm. Cured polyimide film was cut into cantilever shapes,which were further used to assemble the sensor. The amorphous wires (30,50,100 μm diameter, Aichi-steel, Japan) and liquid metal (1.5 Ω cm−1) in-terconnects were placed at the center of the film, and the two ends of thewires were connected to the external electronics using Cu wires with di-ameter of 0.2 mm. Liquid metal interconnects were based on high-purityalloys of Gallium, Indium, and Tin (99.99%, Beijing Founde Star Sci. &Technol. Co., Ltd, China), which were mixed in the ratio of 68.2:21.8:10 bymass and heated and stirred at 60 °C for 30 min. Small patches of flexi-ble magnets were formed by mixing PDMS (184, Dow Corning, USA) andNdFeB particles (diameter: 50 μm, Xinnuode Co., Ltd, China). After curingand cutting by laser, the composites were magnetized in a pulsed magneticfield of 5 T with a pulse duration of 1 ms (SCH-3540MD Pulse magnetizer,Shanghai Pingye Co Ltd, China). Then, the magnetic patch was located ona cantilever beam. The entire structure was encapsulated in PDMS, whichwas cured at 60 °C for 120 min to package the sensor.Mechanical Characterization: Mechanical tests of the Polyimide,Polystyrene, and Polyurethane substrates (thickness of each substrate:100 μm; width: 1 cm; length: 3 cm; Figure S9, Supporting Information)were conducted by using a computer-controlled material testing machine(Instron 5943, USA) at the rate of 5 mm min−1. Stretching experimentswere done using a laboratory-prepared tensile test machine.Morphological Characterization: SEM images and EDS data of Co-based amorphous wires were taken using microscope Sirion200 (FEI,USA).Magnetic Characterization: The hysteresis loop of the Co-based amor-phous wire was measured by applying a magnetic field along the wire in avibrating sample magnetometer (Lakeshore7410, Lakeshore, USA). TheMI of the amorphous wire was measured in an electromagnet while aGauss meter was used to measure the magnitude of the magnetic field inthe geometric center of the Helmholtz coil. The sensor’s impedance dur-ing the current change was measured by the impedance analyzer (IM3570,HIOKI, Japan).Device Characterization: Sensor performance at small magnetic fields(0–1 mT, Figure 3b): The sensor was fixed in the center of the Helmholtzcoil having 50 turns and 23 mm diameter. The magnetic field in the centerof the coil was calculated as:B =𝜇0N0IR2[R2 +(d2)2] 32(3)where 𝜇0, N0, I, R, and d represent vacuum permeability, number ofturns, current, spacing of two coils, and diameter of coil, respectively. Theimpedance change of the sensor with the change of the current throughthe coil was measured by using an impedance analyzer.Sensor performance at strong magnetic fields (0.5 mT–400 mT,Figure 3c): The sensor was fixed in an electromagnet. A Gauss meter (PF-35, Litian Co, Ltd., China) was used to measure the magnitude of themagnetic field in the centre between poleshoes of the electromagnet. Animpedance analyzer was used to measure the impedance of the sensorinduced due to magnetic field change by the current.Demonstrators: The sensor was fixed on the nail and an impedanceanalyzer (IM3570, HIOKI, Janpan) was used to measure the impedancechange of the sensor. Data obtained from the impedance analyzer wereprocessed using LabVIEW software. The angle between the sensor andthe geomagnetic field direction changes upon the finger movement. Thissignal was used to control the movement of a car in a video game. A smallpatch of a flexible magnet (0.5 cm × 1 cm) was fixed on the arm with aPU tape. When the finger approaches a progressively larger electromag-net (threshold set at 200 mT), the software was programmed to issue awarning signal.Supporting InformationSupporting Information is available from the Wiley Online Library or fromthe author.AcknowledgementsThis research was partially supported by the National Natural Sci-ence Foundation of China (U20A6001, M-0152, U1909215, 51931011,62174165, 52127803, U22A2075, U22A20248, 51971233, 52201236 and52105286), the External Cooperation Program of Chinese Academy of Sci-ences (174433KYSB20200013), K.C. Wong Education Foundation (GJTD-2020-11), Chinese Academy of Sciences Youth Innovation PromotionAssociation (Y2022080), “Pioneer” and “Leading Goose” R&D Pro-gram of Zhejiang (2022C01032), Zhejiang Provincial Key R&D Program(2021C01183), “High-level talent special support plan” technology innova-tion leading talent project of Zhejiang Province (2022R52004), Natural Sci-ence Foundation of Zhejiang Province (LD22E010002), Zhejiang Provin-cial Basic Public Welfare Research Project (LGG20F010006), Ningbo Sci-entific and Technological Innovation 2025 Major Project (2020Z022),Ningbo Key Research and Development Program (Grant No. 2023Z097),the China Postdoctoral Foundation (2022M723251), German ResearchFoundation (DFG) grants MA 5144/13-1, MA 5144/28-1 and HelmholtzAssociation of German Research Centers in the frame of the HelmholtzInnovation Lab “FlexiSens”.Conflict of InterestThe authors declare no conflict of interest.Data Availability StatementThe data that support the findings of this study are available from the cor-responding author upon reasonable request.Adv. Sci. 2024, 11, 2304525 © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH2304525 (10 of 11) 21983844, 2024, 37, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/advs.202304525 by National Institute For, Wiley Online Library on [09/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advancedscience.comwww.advancedsciencenews.com www.advancedscience.comKeywordsamorphous magnetic wires, magnetic field sensor, magnetosensitivesmart skins, wearable electronics, wide detection rangeReceived: July 5, 2023Revised: October 30, 2023Published online: November 30, 2023[1] J. Li, J. Zhao, J. A. Rogers, Acc. Chem. Res. 2019, 52, 53.[2] M. L. Hammock, A. Chortos, B. C.-K. Tee, J. B.-H. Tok, Z. Bao, Adv.Mater. 2013, 25, 5997.[3] S. Huang, Y. Liu, Y. Zhao, Z. Ren, C. F. Guo, Adv. 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Buscaglia, J. P. Carmo, O. N. Oliveira, IEEE Sens. J. 2023, 26067.Adv. Sci. 2024, 11, 2304525 © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH2304525 (11 of 11) 21983844, 2024, 37, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/advs.202304525 by National Institute For, Wiley Online Library on [09/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advancedscience.comhttps://doi.org/10.1080/0002889778507706 Wearable Magnetic Field Sensor with Low Detection Limit and Wide Operation Range for Electronic Skin Applications 1. Introduction 2. Results and Discussions 2.1. Concept of Wearable Magnetic Field Sensor 2.2. Preparation of Flexible Magnetic Sensor 2.3. Structure and Performance Characterization of the Magnetic Field Sensor 2.4. Magnetic Field Detection Performance of the Flexible Magnetic Field Sensor 2.5. Applications of Flexible Magnetic Field Sensors 3. Conclusion 4. Experimental Section Supporting Information Acknowledgements Conflict of Interest Data Availability Statement Keywords