Ultralow-force-driven polarization switching in molecular ferroelectrics

Manipulation of ferroelectric domains is essential for advancing ferroelectric electronics. Mechanical switching offers an effective route for nanoscale domain control, yet conventional inorganic ferroelectrics typically require micronewton-level forces applied by nanoscale probes, generating GPa local pressures that risk material damage and make it challenging to mechanically generate large-area ferroelectric domain patterns. Overcoming this limitation demands ferroelectrics capable of responding to extremely small mechanical stimuli. Here, we demonstrate ultralow-force-driven polarization switching in the molecular ferroelectric (3,3-difluorocyclobutylammonium)2CuCl4, a two-dimensional organic-inorganic hybrid perovskite. Domain switching is achieved with an applied force of only 25 nN—corresponding to a local pressure below 20 MPa, orders of magnitude lower than that required for inorganic oxide ferroelectrics. This exceptionally low mechanical threshold arises from the intrinsic structural compliance and flexibility of molecular ferroelectrics. Moreover, the remarkably small switching force also enables ultrasound-driven domain modification. These results create new opportunities for molecular ferroelectrics in mechanoelectrical electronics, energy harvesting, and ultrasonic catalysis.