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.
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
Significant effort has been put into the antenna miniaturization. Electrically small antennas still suffer from various issues, such as a relatively large physical size. Hence, antenna designs based on different radiation mechanisms have attracted more attention, and the mechanical antenna is one feasible solution. A review of the conventional antenna miniaturization and developments in miniaturization methods is presented in this paper. The topic of focus is on mechanical resonance and magnetoelectric (ME) coupling within the piezoelectric/ferromagnetic ME composite. This Perspective discusses the challenges and possible solutions for employing mechanical antennas for practical applications; it concludes an up-to-date discussion of current ME antenna applications for commercial and military communication devices and future applications.
Electrical stimulation via invasive microelectrodes is commonly used to treat a wide range of neurological and psychiatric conditions. Despite its remarkable success, the stimulation performance is not sustainable since the electrodes become encapsulated by gliosis due to foreign body reactions. Magnetic stimulation overcomes these limitations by eliminating the need for a metal-electrode contact. Here, we demonstrate a novel microfabricated solenoid inductor (80 µm × 40 µm) with a magnetic core that can activate neuronal tissue. The characterization and proof-of-concept of the device raise the possibility that micromagnetic stimulation solenoids that are small enough to be implanted within the brain may prove to be an effective alternative to existing electrode-based stimulation devices for chronic neural interfacing applications.
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