pH- and near-infrared light-responsive,biomimetic hydrogels from aqueous dispersions of carbon nanotubes

Owing to their low flexibility,poor processability and a lack of responsiveness,inorganic materials are usually non-ideal for constructing a living organism.Hence,to date,lifelike materials with structural hierarchies and adaptive properties usually rely on light and soft organic molecules,although few exceptions have been acquired using two-dimensional(2D)inorganic nanosheets.Herein,with a systematic study on the gelation behavior of carbon-based 0D quantum dots,1D nanotubes,and 3D fullerenes,we find that acidified 1D carbon nanotubes(CNTs)can serve as an alternative building block for fabricating purely inorganic biomimetic soft materials.The as-prepared CNT gels exhibit not only a pH-or photothermal-triggered mechanical and tribological adaptivity,which allows them to simulate the behavior of sea cucumbers,peacock mantis shrimps,and mammalian muscles or cortical bones,but also a unique damping property that is similar to spider’s cuticular pad.Their high elasticity,effective lubrication,excellent biocompatibility,and controllable friction and wear also allow them to function as a new type of smart lubricants,whose tribological properties can be regulated either by its internal pH changes or spatiotemporally by near-infrared(NIR)light irradiations,free of any toxic and flammable base oils or additives.