Mechanically deformable organic ferroelectric crystal with adaptive shape locking

Abstract

The ability of mechanical deformation and adaptive shape locking exerts in bulk crystals would offer great promise for ferroelectrics to enable emerging and exciting applications. However, conventional ferroelectric crystals generally suffer from poorly mechanical properties, inherent brittleness and easy to fracture. Here, by implementing fluorination on negative dipoles, we successfully designed a flexible organic ferroelectric phenylethylammonium trifluoromethanesulfonate (PEA-TFMS) capable of shape-changing and locking with outstanding mechanical deformability in its bulk crystals. To our knowledge, it is the first observation since the discovery of organic ferroelectric crystal triglycine sulfate in 1956. Compared to parent PEA-MS (phenylethylammonium mesylate), fluorination subtly alters ionic orientation and interactions to reorganize dipole arrangement, which not only bring switchable spontaneous polarization but also endow PEA-TFMS crystal with directly macroscopical bent and spiral deformability, making it competitive candidates for flexible and wearable devices. Our work will bring inspiration for obtaining mechanically deformable organic ferroelectric crystals toward flexible electronics.