Low melting point alloy modified polymer composite with sharp stiffness switch for soft actuator

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 & mu;m, 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 (Rf) and shape recovery ratio (Rr) 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 degrees 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.

Automated summary

In this study, a facial PVA coating method was used to fabricate FM phase-changing particles, resulting in stiffness variable polymer composites. The composites showed improved rigid/soft stiffness ratio and excellent shape memory properties. The prepared composites were then applied in a 3D printing soft actuator, which exhibited fast heating-cooling time and high load capacity, demonstrating excellent actuate behavior and stiffness switchable ability.