Search for: All records

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.

 

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. 

Miniaturized piezoelectric/magnetostrictive contour‐mode resonators are effective magnetometers by exploiting the ΔEeffect. With dimensions of ≈100–200 µm across and <1 µm thick, they offer high spatial resolution, portability, low power consumption, and low cost. However, a thorough understanding of the magnetic material behavior in these devices is lacking, hindering performance optimization. This manuscript reports on the strong, nonlinear correlation observed between the frequency response of these sensors and the stress‐induced curvature of the resonator plate. The resonance frequency shift caused by DC magnetic fields drops off rapidly with increasing curvature: about two orders of magnitude separate the highest and lowest frequency shift in otherwise identical devices. Similarly, an inverse correlation with the quality factor is found, suggesting a magnetic loss mechanism. The mechanical and magnetic properties are theoretically analyzed using magnetoelastic finite‐element and magnetic domain‐phase models. The resulting model fits the measurements well and is generally consistent with additional results from magneto‐optical domain imaging. Thus, the origin of the observed behavior is identified and broader implications for the design of nanomagnetoelastic devices are derived. By fabricating a magnetoelectric nanoplate resonator with low curvature, a record‐high DC magnetic field sensitivity of 5 Hz nT^–1is achieved.