An official website of the United States government
Abstract Wireless power transfer (WPT) has received increasing attention primarily as a means of recharging batteries in the last few decades. More recently, magnetoelectric (ME) structures have been investigated as alternative receiving antennas in WPT systems. ME structures can be particularly useful for small scale devices since their optimal size is much smaller than traditional receiving coils for a given operating frequency. WPT systems using ME laminate receivers have been shown to be helpful in wirelessly powering various sensors and biomedical implants. In recent years, a large number of studies have been conducted to improve the performance of ME composites, in which various configurations have been proposed, along with the use of different magnetostrictive and piezoelectric materials. In addition, many efforts have been devoted to miniaturizing ME devices. An essential obstacle to overcome is to eliminate the need for a DC bias field that is commonly required for the operation of ME structures. In this review paper, we will discuss the basic principle of ME effects in composites, materials currently in use, various ME receiver structures, performance measures, limitations, challenges, and future perspectives for the field of WPT. Furthermore, we propose a power figure of merit which we use to compare recent ME WPT research papers.
more »
« less
Powering Wireless Sensors Using Magnetoelectric Wireless Power Transfer
This paper presents a method to wirelessly power sensors using magnetoelectric (ME) structures as receivers. ME receivers consist of composites of magnetostrictive (MS) and piezoelectric material. Using ME receivers, as opposed to inductively coupled coils, is useful when a combination of small size and low frequency are desirable. Most ME receivers require a large DC magnetic field bias for high-performance operation. We present magnetization grading approach with multiple layers of MS material that results in high-performance structures with no DC magnetic field bias required. Our device produces 600 microwatts when excited by a 100 microtesla AC magnetic field at 192.3 kHz. The device is 12.4 mm X 5 mm X 1 mm. The corresponding normalized power density is 10.71 mWcm−3Oe−2, which is the highest reported to our knowledge.
more »
« less
- Award ID(s):
- 2320320
- PAR ID:
- 10637144
- Publisher / Repository:
- IEEE
- Date Published:
- ISSN:
- 2168-9229
- ISBN:
- 979-8-3503-6351-7
- Page Range / eLocation ID:
- 1 to 4
- Format(s):
- Medium: X
- Location:
- Kobe, Japan
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
To maximize the capabilities of minimally invasive implantable bioelectronic devices, we must deliver large amounts of power to small implants; however, as devices are made smaller, it becomes more difficult to transfer large amounts of power without a wired connection. Indeed, recent work has explored creative wireless power transfer (WPT) approaches to maximize power density [the amount of power transferred divided by receiver footprint area (length × width)]. Here, we analyzed a model for WPT using magnetoelectric (ME) materials that convert an alternating magnetic field into an alternating voltage. With this model, we identify the parameters that impact WPT efficiency and optimize the power density. We find that improvements in adhesion between the laminated ME layers, clamping, and selection of material thicknesses lead to a power density of 3.1 mW/mm2, which is over four times larger than previously reported for mm-sized wireless bioelectronic implants at a depth of 1 cm or more in tissue. This improved power density allows us to deliver 31 and 56 mW to 10 and 27-mm2 ME receivers, respectively. This total power delivery is over five times larger than similarly sized bioelectronic devices powered by radiofrequency electromagnetic waves, inductive coupling, ultrasound, light, capacitive coupling, or previously reported magnetoelectrics. This increased power density opens the door to more power-intensive bioelectronic applications that have previously been inaccessible using mm-sized battery-free devices.more » « less
-
As the size of biomedical implants and wearable devices becomes smaller, the need for methods to deliver power at higher power densities is growing. The most common method to wirelessly deliver power, inductively coupled coils, suffers from poor power density for very small-sized receiving coils. An alternative strategy is to transmit power wirelessly to magnetoelectric (ME) or mechano-magnetoelectric (MME) receivers, which can operate efficiently at much smaller sizes for a given frequency. This work studies the effectiveness of ME and MME transducers as wireless power receivers for biomedical implants of very small (<2 mm3) size. The comparative study clearly demonstrates that under existing safety standards, the ME architecture is able to generate a significantly higher power density than the MME architecture. Analytical models for both types of transducers are developed and validated using centimeter scale devices. The Institute of Electrical and Electronics Engineers (IEEE) and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) standards were applied to the lumped elements models which were then used to optimize device dimensions within a 2 mm3 volume. An optimized ME device can produce 21.3 mW/mm3 and 31.3 W/mm3 under the IEEE and ICNIRP standards, respectively, which are extremely attractive for a wide range of biomedical implants and wearable devices.more » « less
-
The magnetoelectric effect (ME) is an important strain mediated-phenomenon in a ferromagnetic-piezoelectric composite for a variety of sensors and signal processing devices. A bias magnetic field, in general, is essential to realize a strong ME coupling in most composites. Magnetic phases with (i) high magnetostriction for strong piezomagnetic coupling and (ii) large anisotropy field that acts as a built-in bias field are preferred so that miniature, ME composite-based devices can operate without the need for an external magnetic field. We are able to realize such a magnetic phase with a composite of (i) barium hexaferrite (BaM) with high magnetocrystalline anisotropy field and (ii) nickel ferrite (NFO) with high magnetostriction. The BNx composites, with (100 − x) wt.% of BaM and x wt.% NFO, for x = 0–100, were prepared. X-ray diffraction analysis shows that the composites did not contain any impurity phases. Scanning electron microscopy images revealed that, with an increase in NFO content, hexagonal BaM grains become prominent, leading to a large anisotropy field. The room temperature saturation magnetization showed a general increase with increasing BaM content in the composites. NFO rich composites with x ≥ 60 were found to have a large magnetostriction value of around −23 ppm, comparable to pure NFO. The anisotropy field HA of the composites, determined from magnetization and ferromagnetic resonance (FMR) measurements, increased with increasing NFO content and reached a maximum of 7.77 kOe for x = 75. The BNx composite was cut into rectangular platelets and bonded with PZT to form the bilayers. ME voltage coefficient (MEVC) measurements at low frequencies and at mechanical resonance showed strong coupling at zero bias for samples with x ≥ 33. This large in-plane HA acted as a built-in field for strong ME effects under zero external bias in the bilayers. The highest zero-bias MEVC of ~22 mV/cm Oe was obtained for BN75-PZT bilayers wherein BN75 also has the highest HA. The Bilayer of BN95-PZT showed a maximum MEVC ~992 mV/cm Oe at electromechanical resonance at 59 kHz. The use of hexaferrite–spinel ferrite composite to achieve strong zero-bias ME coupling in bilayers with PZT is significant for applications related to energy harvesting, sensors, and high frequency devices.more » « less
-
Most of the next-generation implantable medical devices that are targeting sub-mm scale form factors are entirely powered wirelessly. The most commonly used form of wireless power transfer for ultra-small receivers is inductive coupling and has been so for many decades. This might change with the advent of novel microfabricated magnetoelectric (ME) antennas which are showing great potential as high-frequency wireless powered receivers. In this paper, we compare these two wireless power delivery methods using receivers that operate at 2.52 GHz with a surface area of 0.043 mm2 . Measurement results show that the maximum achievable power transfer of a ME antenna outperforms that of an on-silicon coil by approximately 7 times for a Tx-Rx distance of 2.16 and 3.3 times for a Tx-Rx distance of 0.76 cm.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/SENSORS60989.2024.10785003
