Quantifying Structure–Property Relationships in Ferroelectric Polymers Toward High‐Performance Soft Robots

ABSTRACT Owing to their excellent electromechanical (EM) response, poly(vinylidene fluoride‐trifluoroethylene) (P(VDF‐TrFE))–based ferroelectric polymers (FEPs) are extensively utilized in soft actuators. Currently, the strain ( S 33 ) of FEPs is mostly identified as electrostriction and described by S 33 = Q 33 P 2 . Wherein, Q 33 represents the electrostriction coefficient, P is polarization, and Q 33 is mainly derived from data fitting. However, this approach fails to establish a connection between the composition and structure of FEPs, hindering the design of FEPs with higher EM response performance. This study introduces an effective model that quantitatively correlates the structural parameter interplanar spacing ( d ) to the EM response, namely Q 33 = 100(Δ d / d 0 +1) × Q 33(s) , where d 0 = 4.31 Å, Q 33(s) = −0.54 m 4 /C 2 are from single P(VDF‐TrFE). Guided by this model, we tailored the electrical properties and d of FEPs by incorporating 1,5‐Dihydroxy‐2,2,3,3,4,4‐Hexafluoropentane (HFPD), which results in a substantial improvement in the S 33 by up to 100%. The composite films show promising application in fabricating high‐performance soft robots, including a biomimetic crawler (with a ultra‐fast crawling speeds of 27 cm/s) and a biomimetic butterfly (with a thrust‐to‐weight ratio of 0.71). Overall, our findings offer new insights for designing FEPs with superior EM responses, potentially driving notable advancements in flexible actuators.