Qi Li,Weixuan Liu,Canhui Yang,Ping Rao,Pengyu Lv,Huiling Duan,Wei Hong
Robust adhesion to and effortless removal from various substrates are of great importance to soft adhesives in myriad applications. However, controlled regulation between strong attachment and easy detachment in a same system remains challenging. Herein, we report a kirigami-inspired approach to control adhesion with high directional asymmetry. By inscribing a specially designed labyrinth pattern in an adhesive film , the adhesion is enhanced against peeling along a particular direction – the peak peel force builds up at a much smaller peeling angle, and the adhesion energy climbs through in-plane elastic dissipaters. Such a mechanism is inactive when the adhesive is peeled in the opposite direction, and easy detachment is experienced. The underlying physics is elucidated via theoretical and numerical analyses and verified through experiments by using hydrogel adhesives with different elastic moduli and geometric parameters . The asymmetric adhesion can be further enhanced over soft substrates or by designing hierarchical structures – increases by up to 22 folds in strength and 7 folds in energy have been observed. The proposed mechanism is universally applicable to various intermolecular interactions and different loading modes, and can pave the way to engineering new adhesives with superior yet controllable adhesion performance.
Reversible shape memory polymers (SMPs) have received extensive attention because of their unique deformation mechanisms and diverse shape-changing behaviors. However, the traditional methods of fabricating reversible SMPs usually result in the limitation of the accessible shapes and the corresponding shape-shifting behaviors. Herein, a reversible SMP with two crystalline phases is digital light-cured via thiol-acrylate chemistry with the assist of a digital light processing (DLP) technology. Thus, a set of special geometric patterns can be obtained by digitally defined exposure regions with a specified time, allowing the achievement of the 3D kirigami or origami reversible actuation. In addition, this strategy can be extended to the emerging advanced 3D or 4D printing technologies by introducing z-axis dimension or time gradient, facilitating the fabrication of sophisticated reprogrammable reversible shape memory devices, including 4D printed grabber and 3D printed movable cartoon character. Our approach based on DLP enables the rapid and precise manipulation of shape-changing materials, which can extend the possibilities for future development in aerospace and other potential applications.
To alleviate the dilemma of plastic recycling, the development of sustainable bioplastics that are compatible with the environment throughout the whole material life cycle has received widespread attention. We report a vacuum-assisted filtration method for preparation of high-strength bioplastic films made from hydrophobic cellulose nanofibers that were obtained by esterification of natural cellulose with dodecenylsuccinic anhydride in recyclable deep eutectic solvent (triethylmethylammonium chloride/imidazole). The tensile strengths of the resultant hydrophobic films were 150.8 MPa and 94.8 MPa under dry and humid conditions, respectively. Importantly, these films could be programmed into various shapes, such as “U” shaped bracket, helix, and ring via a hydrosetting method and the strong hydrogen bonding interactions between cellulose nanofibers contributed to shape fixation. Benefiting from their hydroplastic properties, various shapes of bioplastic films could be reversibly engineered by kirigami, origami, and embossing. Meanwhile, the disposal of waste films followed the recycling route to regain hydrophobic cellulose nanofibers. This work provided a facile approach for the preparation of high-strength and recyclable hydroplastic cellulose nanofiber films.
危险品化学品经营许可证（带存储）