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Ultra-compact wireless implantable medical devices are in great demand for healthcare applications, in particular for neural recording and stimulation. Current implantable technologies based on miniaturized micro-coils suffer from low wireless power transfer efficiency (PTE) and are not always compliant with the specific absorption rate imposed by the Federal Communications Commission. Moreover, current implantable devices are reliant on differential recording of voltage or current across space and require direct contact between electrode and tissue. Here, we show an ultra-compact dual-band smart nanoelectromechanical systems magnetoelectric (ME) antenna with a size of 250 × 174 µm2 that can efficiently perform wireless energy harvesting and sense ultra-small magnetic fields. The proposed ME antenna has a wireless PTE 1–2 orders of magnitude higher than any other reported miniaturized micro-coil, allowing the wireless IMDs to be compliant with the SAR limit. Furthermore, the antenna’s magnetic field detectivity of 300–500 pT allows the IMDs to record neural magnetic fields.

Since the revival of multiferroic laminates with giant magnetoelectric (ME) coefficients, a variety of multifunctional ME devices, such as sensor, inductor, filter, antenna etc. have been developed. Magnetoelastic materials, which couple the magnetization and strain together, have recently attracted ever-increasing attention due to their key roles in ME applications. This review starts with a brief introduction to the early research efforts in the field of multiferroic materials and moves to the recent work on magnetoelectric coupling and their applications based on both bulk and thin-film materials. This is followed by sections summarizing historical works and solving the challenges specific to the fabrication and characterization of magnetoelastic materials with large magnetostriction constants. After presenting the magnetostrictive thin films and their static and dynamic properties, we review micro-electromechanical systems (MEMS) and bulk devices utilizing ME effect. Finally, some open questions and future application directions where the community could head for magnetoelastic materials will be discussed.

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9 10 -Abstract 11 Ultra-compact wireless implantable medical devices (IMDs) are in great demand for healthcare 12 applications, in particular for neural recording and stimulation. Current implantable technologies 13 based on miniaturized micro-coils suffer from low wireless power transfer efficiency (PTE) and 14 are not always compliant with the specific absorption rate imposed by the Federal Communications 15 Commission, particularly for deep brain implantation where field attenuation and tissue loss are 16 significant. Moreover, current implantable devices are reliant on recordings of voltage or current. 17This has two major weaknesses: 1) the necessary direct contact between electrode and tissue 18 degrades over time due to electrochemical fouling and tissue reactions, and 2) the necessity for 19 differential recordings across space. Here, we report, for the first time, an ultra-compact dual-band 20 smart nanoelectromechanical systems magnetoelectric (ME) antenna with a size of 250×174 µm 2 21 that can efficiently perform wireless energy harvesting and sense ultra-small magnetic fields such 22 designs and different operating frequencies. The ME antenna is based on ME FBAR (thin film 56 bulk acoustic wave resonator) working at 2.5 GHz; while the ME sensor is based on a ME NPR 57 (nano-plate resonator) with interdigitated electrode and an operation frequency of 215MHz. In this 58 paper we present the first ever smart ME antenna with unprecedented characteristics that are ideal 59 for IMDs: (1) ultra-compact antenna for highly efficient wireless power transfer efficiency and 60 data communication at GHz; (2) ultra-sensitive magnetometer capable of sensing picoTesla low-61 frequency fields by using MHz resonance; and (3) simultaneous operation at two different 62