Harvesting magnetic energy from the environment is becoming increasingly attractive for being a renewable and inexhaustible power source, ubiquitous and accessible in remote locations. In particular, magnetic harvesting with polymer-based magnetoelectric (ME) materials meet the industry demands of being flexible, showing large area potential, lightweight and biocompatibility. In order to get the best energy harvesting process, the extraction circuit needs to be optimized in order to be useful for powering devices. This paper discusses the design and performance of five interface circuits, a full-wave bridge rectifier, two Cockcroft–Walton voltage multipliers (with 1 and 2 stages) and two Dickson voltage multipliers (with 2 and 3 stages), for the energy harvesting from a Fe _61.6 Co _16.4 Si _10.8 B _11.2 (Metglas)/polyvinylidene fluoride/Metglas ME composite. Maximum power and power density values of 12 μ W and 0.9 mW cm ⁻³ were obtained, respectively, with the Dickson voltage multiplier with two stages, for a load resistance of 180 kΩ, at 7 Oe DC magnetic field and a 54.5 kHz resonance frequency. Such performance is useful for microdevice applications in hard-to-reach locations and for traditional devices such as electric windows, door locking, and tire pressure monitoring.

The development of a DC magnetic field sensor based on a magnetoelectric (ME) PVDF/Metglas composite is reported. The ME sensing composite has an electromechanical resonance frequency close to 25.4 kHz, a linear response (r ² = 0.997) in the 0-2 Oe DC magnetic field range, and a maximum output voltage of 112 mV (ME voltage coefficient α ₃₃ of ≈30 V·cm ^-1 ·Oe ^-1 ). By incorporating a charge amplifier, an AC-RMS converter and a microcontroller with an on-chip analog-to-digital converter, the ME voltage response is not distorted, the linearity is maintained, and the ME output voltage increases to 3.3 V (α _33effective = 1000 V·cm ^-1 ·Oe ^-1 ). The sensing device, including the readout electronics, has a maximum drift of 0.12 Oe with an average total drift of 0.04 Oe, with a sensitivity of 1.5 V·Oe ^-1 (15 kV·T ^-1 ), and a 70 nT resolution. This feature is for the first time reported on a polymer-based ME device and compares favourably with a reference Hall sensor that showed a maximum drift of 0.07 Oe and an average error of 0.16 Oe, 5 V·T ^-1 sensitivity, and 2 μT resolution. Such properties allied to the accurate measurement of the DC magnetic field (H _DC ) in the 0-2 Oe range make this polymer-based device very attractive for applications, such as Earth magnetic field sensing, digital compasses, navigation, and magnetic field anomaly detectors, among others.