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Stimuli-sensitive hydrogels have been intensively studied because of their potential applications in drug delivery, cell culture, and actuator design. Although hydrogels with directed unidirectional response, i.e. capable of bending actuated by different chemical components reaction in response to several stimuli including water and electric fields, these hydrogels are capable of being actuated in one direction only by the stimulus. By contrast the challenge of building a device that is capable of responding to the same cue (in this case a temperature gradient) to bend in either direction remains unmet. Here, inspired by the structure of pine cone scales, we design a temperature-sensitive hydrogel with bending directed an imposed fishing line. The layers with same PNIPAAm always shrinks in response to the heat. Even the layers made with different chemical property, bends away from a warm surface, whether the warm surface is applied at its upper or lower boundary. To design the bending hydrogel we exploited the coupled responses of the hydrogel; a fishing line intercalating structure and change its construction. In addition to revealing a new capability of stimulus sensitive hydrogels, our study gives insight into the structural features of pine cone bending., Competing Interests: The authors have declared that no competing interests exist.

Polypyrrole (PPy) is a promising conductive polymer (CP) with electrical versatility, easy synthesis and functionalization, stability, and biocompatibility. Diverse architectures have been adopted to improve PPy performance, but the direct and precise patterning of various architectures remains challenging. Here, the unique formation of a PPy membrane on the air/water interface of a droplet solution containing ammonium persulfate and phytic acid is investigated. When a PPy thin film forms on the air/water interface, the top of the droplet rapidly flattens. The formation procedure and final structure of the PPy thin film are visualized and quantitatively investigated. Unlike the typical globular structure of PPy, the self‐assembled PPy film surface fabricated in this study is very organized and regularly shaped. This well‐ordered membrane may have a very high buckling strength greater than the surface tension of the solution. The proposed precise fabrication method is simple and inexpensive for fabricating patterned functional membranes. These results provide new insight into the fabrication of CP and their applications in various practical electromaterial engineering fields. The unique formation of polypyrrole (PPy) thin film on the air/water interface of a droplet solution containing ammonium persulfate and phytic acid is investigated. The self‐assembled PPy film surface is very organized and regularly shaped. Considering that the precise patterning of various architectures hinders the design of conductive polymers, the proposed method is inexpensive and simple for fabricating patterned functional membranes. [ABSTRACT FROM AUTHOR]