In the last decade, magnetoelectric (ME) polymer films have been developed by including zero-dimensional or one-dimensional magnetostrictive fillers in a piezoelectric polymer matrix. Existing reports on ME polymer films reveal that the shape of the magnetostrictive fillers is a critical determinant of the polymeric phase conformation, strain transfer between the piezoelectric and magnetostrictive phases, and dipole alignment in the films. In this study, to investigate the effect of two-dimensional (2D) magnetostrictive fillers on piezoelectric, magnetic, and magnetoelectric responses, 3-2 type ME films were prepared using CoFe2O4-intercalated graphene oxide (CFO-i-GO) fillers and poly(vinylidene fluoride) (PVDF) polymers. The 2D fillers of CFO-i-GO were hydrothermally synthesized by CFO intercalation into the interlayers of GO sheets with different lateral sizes, which were controlled by ultrasonication treatment. It was found that the large-lateral-size GO (LGO), medium-lateral-size GO (MGO), and small-lateral-size GO (SGO) fillers in the PVDF-based ME films exhibited a lateral size effect on CFO intercalation, polymeric phase conformation, dipole alignment, and magnetoelectric responses. A maximum ME coefficient (αME) of 3.0 mV/cm∙Oe was achieved with a strong linearity (r2) of 0.9992 at an off-resonance frequency (f) of 1 kHz and applied direct current (dc) magnetic field (Hdc) of ± 1000 Oe. The 3-2 type polymer-based ME films with reliable ME responses have potential for use in high-feasibility ME devices for biomedical sensing applications.

Multiferroic materials exhibited more than one ferroic properties of piezoelectric, magnetostrictive, and magnetoelectric. Among the multiferroic materials, magnetoelectric (ME) materials coexisting ferroelectric and ferromagnetic properties has attracted great attention due to its unique applications such as energy harvesters, highly-sensitive magnetic sensors, actuators, memory devices. With the increase in demand of flexible and multifunctional electronic devices, polymer-based ME composites consisting of ferroelectric polymer matrix and ferromagnetic ceramic nanofillers have been developed by optimization of materials, structure, and process. In this review, we described research history and feasible applications for the polymer-based ME composites. We believe that the polymer-based ME composites can be a potential candidate for self-powered energy and sensing devices relevant to the fourth industrial revolution in the near future.

Particulate matter (PM) emission is a serious drawback in several fields, threatening public health and the living environment worldwide. In the last decade, electrostatic interaction-based air filters have been developed owing to their effective filtration performance and low energy consumption. In this study, to develop ME-based electrostatic air filters, we developed polymer composites of poly(vinylidene fluoride-cotrifluoroethylene)/porous-Ni {P(VDF-TrFE)/p-Ni} by investigating the PM filtration efficiency and air flow resistance. P(VDF-TrFE)/p-Ni composites were prepared through a piezoelectric polymer coating of magnetostrictive p-Ni templates. In particular, to induce a sufficient surface charge in the composites for effective air filtering, the β-phase conformation and crystallization of P(VDF-TrFE) were enhanced by optimizing the dip-coating solutions. Moreover, the interfacial strain propagation between P(VDF-TrFE) and porous-Ni was investigated using varying weight ratios of P(VDF-TrFE)/p-Ni. Consequently, the ME-based composites with reusability were observed to exhibit maximum PM filtration efficiencies of 79.2% (PM 2.5 ) and 83.9% (PM 10 ) with a low pressure of 49 Pa. From the results, it was noted that the ME-based air filters of P(VDF-TrFE)/p-Ni can provide feasibility for more practical PM 2.5 removal of fine dust.