Encapsulated Magnetoelectric Composites for Wirelessly Powered Brain Implantable Devices

Magnetoelectric devices are readily employed as sensors, actuators, and antennas, but typically exhibit low power output. This paper presents considerations for the viability of magnetoelectric composites for wireless power transfer in neural implantation. This is accomplished herein by studying different types of biocompatible encapsulants for magnetoelectric devices, their impact on the output voltage of the composites, and the rigidity of the materials in the context of tissue damage. Simulation results indicate that a polymer encapsulant, rather than creating a substrate clamping effect, increases the voltage output of the magnetoelectric, which can be further improved by careful polymer selection. These attributes are modelled using the finite element method (FEM) with COMSOL Multiphysics. The addition of a 0.2 mm poly(ethyl acrylate) encapsulating layer increases the piezoelectric voltage to 3.77 V AC output at a magnetic field strength of 200 Oe, as the magnetostrictive layer deforms inside the flexible outer polymer. Comparing voltage conditioning circuits, the output is sufficient for low-voltage neuronal stimulation when employing a simple bridge rectifier which boasts minimal charging time and ripple voltage around 1 mV.