Self‐assembled membranes with periodic wrinkled patterns are the critical building blocks of various flexible electronics, where the wrinkles are usually designed and fabricated to provide distinct functionalities. These membranes are typically metallic and organic materials with good ductility that are tolerant of complex deformation. However, the preparation of oxide membranes, especially those with intricate wrinkle patterns, is challenging due to their inherently strong covalent or ionic bonding, which usually leads to material crazing and brittle fracture. Here, wrinkle‐patterned BaTiO3 (BTO)/poly(dimethylsiloxane) membranes with finely controlled parallel, zigzag, and mosaic patterns are prepared. The BTO layers show excellent flexibility and can form well‐ordered and periodic wrinkles under compressive in‐plane stress. Enhanced piezoelectricity is observed at the sites of peaks and valleys of the wrinkles where the largest strain gradient is generated. Atomistic simulations further reveal that the excellent elasticity and the correlated coupling between polarization and strain/strain gradient are strongly associated with ferroelectric domain switching and continuous dipole rotation. The out‐of‐plane polarization is primarily generated at compressive regions, while the in‐plane polarization dominates at the tensile regions. The wrinkled ferroelectric oxides with differently strained regions and correlated polarization distributions would pave a way toward novel flexible electronics.
Models and instrumental data indicate that the spatial and temporal variations of snow cover are significantly related to atmospheric circulation (e.g. the AO/NAO). Here, we present historical snow anomaly events during the past two millennia that provide a unique temporal window to studying long‐term AO/NAO, a prominent phenomenon in wintertime. Direct descriptions such as “no snow during the winter” and “pray God for snow” are interpreted as convincing evidence for snow anomalies. The variations of positive/negative snow abnormal events show clear decadal to century variations during the past two millennia. Based on the previous instrumental research and comparison with other reconstruction data, we suggest the Index of Abnormal Snow (IAS) may be an AO‐like atmospheric variability. The winter during the Medieval Warm Period (MWP) (AD 900–1300) might be strongly influenced by a predominantly positive AO with less snow condition, whereas the Little Ice Age (LIA) (AD 1300–1900) by negative AO concomitant with heavier snowfalls in East Asia. Our data show that a warm climate period (the MWP)/a cold period (the LIA) can be perturbed by a cold spell/a warm spell which are linked with a change in atmospheric circulation. Low‐frequency variability of snow records may be intrinsic to the natural climate system. Although the dynamic mechanisms linking snow anomalies with atmospheric circulation (the AO/NAO, the PDO) is unclear on the decadal to century time scales, Pacific Ocean may play an important role in regulating atmospheric circulations since the IAS is highly correlated with the reconstruction of PDO.
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