Tensegrity-inspired polymer films: progressive bending stiffness through multipolymeric patterning

Abstract

Materials with J-shaped stress-strain behavior under uniaxial stretching have been developed using various designs; in these materials, the strength increases as the deformation progresses. On the other hand, polymer materials that progressively stiffen under bending are far less explored, and a systematic approach to achieving this behavior has not yet been developed. To address this gap, membrane tensegrity structures, which achieve structural stability by balancing compressive forces in rods and tensile forces in membranes, were examined. Notably, some of these structures exhibit increased stiffness under bending. Using a multipolymer patterning technique, we developed a functional polymer film exhibiting membrane tensegrity-like properties that stiffened under bending. This effect resulted from the membrane tension generated by rod protrusions and a likely increase in the second moment of area at regions with maximum curvature. In this study, the membrane tensegrity concept and multipolymer patterning were used to design functional polymer films that progressively stiffened under bending. This behavior was achieved through the rod protrusions generating tensile forces in the membrane and likely changes in the second moment of the area in the maximum curvature regions. The use of these films can provide a systematic approach to dynamic stiffness under nonuniaxial deformation, enabling applications in soft robotics, adaptive supports, and devices requiring tailored mechanical responses.