The high elasticity exhibited by polymer elastomers is a unique mechanical property, which has an irreplaceable position in various fields of daily life and national economy. The high deformation of polymer elastomers is mainly derived from the huge difference in the mean square end distance of linear polymer segments in the curled and straightened state, which is a kind of entropy elasticity. However, in inorganic materials, due to strong internal covalent bonds, ionic bonds, metal bonds and other strong forces, the elastic deformation of inorganic materials is much smaller. Therefore, how to prepare highly stretchable pure inorganic elastomer has been a difficult problem for a long time.
After years of research, the team of professors Gao Chao from the Department of Polymer Science and Engineering of Zhejiang University has recently made breakthrough progress. The team designed and prepared a highly stretchable all-carbon aerogel elastomer with ultra-low density (5.7 mg cm-3), high stretch ratio (~200%), and low energy loss (~0.1, lower than silicon Rubber), excellent fatigue resistance (106 cycles), wide temperature range (-198~500℃) and other excellent properties.
Figure 1. Highly stretchable full carbon aerogel elastomer
The team proposed a multi-stage collaborative assembly method to realize this highly stretchable all-carbon aerogel. It has a four-level structure. From the macro to the micro, there are the first-level truss structure, the second-level polygon cells, the third-level buckled struts, and the fourth-level two-level truss structure. Binary molecular blocks (as shown in Figure 2). Among them, the first-level frame structure is controlled by graphene 3D printing technology to obtain periodic structures with different patterns to achieve different deformation modes; the second-level polygonal unit is the basic composition of graphene aerogel materials Unit; the third-level buckling structure is obtained through a restricted reduction process, which can be adjusted by different compression rates; the fourth-level structure is composed of the cooperative assembly of graphene and carbon nanotubes, and the synergy can be effectively enhanced The aerogel structural unit wall improves the elastic modulus and fatigue resistance of the aerogel elastomer.
Figure 2. Highly stretchable all-carbon aerogel elastomer is made by multi-stage collaborative assembly method
This all-carbon aerogel elastomer has excellent fatigue resistance. It can be cycled stably for at least 100 cycles when stretched at 200%; at 100Hz, at 1% strain, it can cycle stably for at least a million times.
Figure 3. Fatigue resistance of all-carbon aerogel elastomer
This new ultra-light carbon-based elastomer is assembled into a strain sensor, which can logically identify complex shape changes. The sensor was first applied to the serpentine robot arm, which can accurately identify the shape and changes of linear, crescent, S and reverse S-shaped.
Figure 4. All-carbon aerogel elastomer assembled into a strain sensor that can be logically identified
This work prepared for the first time a highly stretchable inorganic full-carbon aerogel elastomer, which broadened the concept of elastomers to the inorganic field, improved the high and low temperature aging resistance of the elastomer, and broadened the temperature range for its use. The application in the field of flexible devices, intelligent robots and aerospace has laid a theoretical foundation. At the same time, this multi-stage collaborative assembly method also provides a new design idea for the preparation of other inorganic elastomers.
The Gaochao team cooperated with Professor Wang Hongtao and Zhao Pei of the School of Aeronautics and Astronautics of Zhejiang University to carry out in-situ high-resolution transmission in-situ characterization of the tensile test, which provided direct microscopic experimental evidence for revealing the elastic mechanism.
The paper was published in the journal Nature Communications. The co-first authors are doctoral students Guo Fan and Jiang Yanqiu, and the corresponding authors are researcher Xu Zhen and Professor Gao Chao.
Link to the paper: https://www.nature.com/articles/s41467-018-03268-y