Printable multi-stage variable stiffness material enabled by low melting point particle additives
Fei Long, Yingchun Shao, Zihui Zhao, Mingquan Fang, Zhiyu Zhang, Jianjun Guo, Aihua Sun, Yong Ren*, Yuchuan Cheng*, Gaojie Xu
龙菲，邵迎春，赵自辉，方明权，Zhiyu Zhang，郭建军，孙爱华, 任勇*，程昱川*，许高杰
A majority of biological organisms in nature can adjust their biomechanical energy to adapt the complex environments, but most of the current synthetic composites have limited rigid and flexible states that cannot achieve multi-level and continuous regulation on altering mechanical stiffness. Herein, the direct ink printing (DIW) approach for forming a 4D printable phase-changing elastomer that achieves multi-stable stages in response to a thermal stimulus has been developed. This composite consists of low melting point alloy (LMPA) microparticles incorporated into silicone elastomer (PDMS) using a facile composite manufacturing process. The particles with different melting points amplify the steady stage in flexural modulus under the thermal response, which is desirable for stiffness-changing applications, particularly relevant to soft robotics. Moreover, the composites possess the improved printability in three-dimensional direct printing via adjusting the volume ratio of the raw materials, which circumvents the dilemma that most sample structures are restricted between one- and two-dimensional transformations as well as the conventional craftsmanship are limited by complex production. It is demonstrated as well that the utility of LMPA/PDMS composites has an advantage of multiple stiffness changing at the set-transition temperature for unveiling its brilliant prospects for soft actuators with 4D printing technology.