Yifan Liu,Jiazuo Zhou,Yudong Li,Xiaohan Sun,Ziyao Wang,Haiyue Yang,Chengyu Wang
Gels as compelling soft material shows its promising versatility in actuators, soft electronics, and biomedical sensors. However, most gel materials are too rigid to cope with long-term changing scenarios and specific needs. Inspired by the switchable behavior of bio-behavior of muscle, the study reports a thermodynamically controllable and stiffness-transformative cellulose-salt gel by simple thermal mixing of hydrous salt, cellulose nanofiber, and polyacrylamide. The achieved cellulosic gel with dynamic microstructure presents an amazing stiffness switchability between crystalline state and melted states of 32.38 to 0.02 MPa, as well as the regulable light transmittance between 41.59% and 93.43%. In addition, this cellulose-salt gel has excellent thermal controllable behavior. That is, by controlling the crystallization process, the cellulose-salt gel displays the start-stop releasing-energy behaviors on demand. Enabled by these outstanding properties, the study further demonstrates the promising application of cellulose-salt gel in controllable soft-rigid coupling thermoelectric device, showing the broader implications for wearable electronics aiming at on-demand work.
Yahao Liu,Yuansheng Wang,Xue Yang,Jian Zheng,Wei Huang,Yu Zhang,Xiao Zhang,Xuan Wang
Materials possessing switchable stiffness, particularly dynamically switchable stiffness, have generated a lot of attention in the soft actuator . Herein, we proposed a facial poly (vinyl alcohol) (PVA) coating method to fabricate the micron-sized Field's metal (FM) phase-changing particles with an average particle size of about 1.2 μm, and obtained a series of stiffness variable polymer composites via incorporating FM particles into the designed stiffness variable polymer matrix . Owing to the rapid solid-liquid change and ultra-high modulus of FM, the rigid/soft stiffness ratio of the composites improved to 1442-folds. Moreover, the shape fixity ( R f ) and shape recovery ratio ( R r ) values of the shape memory properties could reach up to ultra-high values of 99.4% and 99.6%, respectively. Subsequently, the prepared composites were selected and used a 3D printing soft actuator as the stiffness variable units. The soft actuator exhibits short heating-cooling time of 36s under 1.2A current and with 4 °C water as the coolant, and it is able to lift a 200 g weight at the rigid state. Furthermore, the stiffness of obtained actuator can achieve high value 779 mN/mm. The results indicate that the obtained soft actuator possesses excellent actuate behavior and stiffness switchable ability. This work might provide faster and more rigid variable stiffness materials for soft actuators application in the real world.
Yu Zhu,Meng-Ting Xu,Zhen-Hua Tang,Feng Chen,De-Yang Wang,Yuan-Qing Li,Shao-Yun Fu
Transformable exo-suits, which are soft and wearable under normal conditions and could increase stiffness dramatically on demand, are significant in personal protection and robotics and also a dream of science-fiction fans. Herein, an ideal candidate material based on a carbon fabric reinforced thermal-hardening hydrogel (CFRTH) composite is proposed for developing transformable exo-suits. The introduction of carbon fabric significantly enhances the mechanical performance of thermal-hardening hydrogel, and empowers the CFRTH composite with an active, rapid and repeatable stiffness switchability. At ambient temperature, the CFRTH composite developed is soft and wearable with excellent flexibility and shape adaptability, while the composite becomes hard and rigid instantaneously as temperature rises. The flexural modulus of the CFRTH composite increases from 2.3 MPa to 539.7 MPa (about 232 times) by applying an electro-thermal stimulus, which endows the composite with good energy absorption/dissipation performance. Compared with the untransformed CFRTH composite, the transformed CFRTH composite under the electro-thermal stimulus exhibits a giant improvement (200%) in the peak force attenuation ratio under dropping ball test and excellent puncture resistance under penetration test and knife stab. Finally, the transformable CFRTH composite demonstrates a high effectiveness in fragile product protection from the impact of steel ball. This study offers a novel and versatile strategy for developing transformable exo-suits which have wearable conformability under normal circumstances and exhibit enhanced stiffness and impact protection performance on-demand through an electro-thermal stimulus.
危险品化学品经营许可证（带存储）