The paper in Nature Communications is here: http://go.nature.com/2CVio4w
Polymeric elastomers find application in a large variety of products such as elastic foams, films or tires, and process unique mechanical properties that set them apart from other materials. Due to the thermal motion, the conformations of polymer chains tend to be coil-like. When external forces are applied, the coiled polymer chains are straightened, lead to large macroscopic deformations. While in inorganic solid materials, the high-strength and short-range of ionic/covalent bond limit the deformation of materials, resulting in small elongations. Furthermore, when inorganic solid materials become lighter, the fragility would severely restrict their stretchability. A question struck us: how to make inorganic aerogel stretchable, just like rubber foams.
To achieve the stretchability of graphene aerogels, two main challenges need to be overcome: the inextensible cell walls and fragile interconnections of graphene aerogels. An intuitional idea is to utilize compression process to generate buckled cell walls (like coiled chains) and synergistic effect to enhance interconnections. We first compressed bulk graphene oxide aerogel to a certain ratio during chemical reduction and the resultant pre-buckled graphene aerogel bulks showed an improved stretching elasticity but still behaved brittle at large strains, because of the non-uniform textured structures in bulks. This negative result reminded us that the microlattice may be a better choice than bulks. So we used the ink-printing technique to directly print three-dimensional lattice graphene aerogels. Excitedly, the pre-buckling method created hierarchical buckled “springs” inside and graphene microlattices become stretchable. We further introduce carbon nanotubes to enhance the stability of these springs and improved the reversibility of stretching, which has been used to relieve compression fragility of graphene aerogels. The hierarchical buckled structures and synergistic reinforcement between graphene and carbon nanotubes work together and finally achieve the highly stretchable carbon aerogels. Beyond the polymeric rubbers, our carbon-based ultralight rubbers kept the stretchable behavior in extreme temperature surroundings, spanning from -180oC (liquid nitrogen) to 500 oC. Through these tries, we are able to turn ultralight carbon aerogels highly stretchable (Figure 1). Our work generates a new ultralight carbon rubber. We exhibited one suitable use as a logically strain sensor that can decipher motion modes of a “snake” robotic arm. Profiting from the integration of ink-printing, the deformation behavior of carbon lattices can be programed to meet various application needs. This ultralight carbon rubber with good electric conductance can be very useful as multifunctional components in actuators, sensors, soft robots and wearable devices.