fig2

Figure 2. (A) In situ SEM image of the BTO film folded to about 180°. (B) SEM images of bending and recovery process of a BTO film. (C) The c/a ratio of freestanding PTO films as a function of uniaxial strain. The inset is schematics of as-grown and stretched polarization state. (D) Electromechanical coupling responses of freestanding BTO films folded and unfolded under an electron beam-induced field. (E) Open circuit voltage (V_oc) and short circuit current density (J_sc) of freestanding BFO device as a function of strain gradient. (F) The bending-expansion and bending-shrinkage effects were observed in upward and downward bent BFO films. Panels A and B reprinted with permission^[61]. Copyright 2019, The American Association for the Advancement of Science. Panel C reprinted with permission^[106]. Copyright 2020, Wiley-VCH. Panel D reprinted with permission^[113]. Copyright 2020, American Chemical Society. Panel E reprinted with permission^[109], 2020, CC BY license. Panel F reprinted with permission^[114], 2022, CC BY license.