We report a systematic study on the magnetoelectric (ME) performance of flexible poly(vinylidene fluoride) (PVDF)-based composites incorporating a Greek key-patterned FeCSi magnetostrictive layer. Four configurations were fabricated: a continuous structure (CS) and three patterned variants with groove widths of 30 \(\mu \) m (G30), 50 \(\mu \) m (G50), and 110 \(\mu \) m (G110). Magnetic characterization revealed that increasing groove width enhanced low-field magnetic susceptibility from 3.9 emu \(\cdot \) g \(^{-1}\cdot \) Oe \(^{-1}\) in CS to 8.2 emu \(\cdot \) g \(^{-1}\cdot \) Oe \(^{-1}\) in G110, a trend supported by MuMax \(^3\) micromagnetic simulations, which showed up to 200% improvement in G50 over CS, depending on field orientation. Mechanical resonance frequencies decreased with increasing groove width, ranging from 153 kHz (CS) to 107 kHz (G110), consistent with a two-layer longitudinal vibration model. ME voltage measurements demonstrated that the G30 design exhibited the highest output (91 mV at \(V_{AC}\) 5 V) and field sensitivity (20.7 mV/Oe), outperforming the continuous and wider groove patterns. Although wider grooves improve magnetic softness via enhanced shape anisotropy, the reduced interfacial area limits strain transfer and thus ME efficiency. These results indicate the importance of balancing magnetic and mechanical factors in patterned structures and establish design principles for high-sensitivity, low-field ME sensors in flexible and wearable applications.
