Novel Stimuli‐Responsive Turbostratic Oxides/Hydroxides for Material‐Driven Robots

Herein, a novel class of high‐performing actuating oxides/hydroxides with turbostratic crystal structures is reviewed. These materials, including nickel hydroxide/oxyhydroxide, cobalt oxides/hydroxides, nickel‐doped cobalt oxides/hydroxides, and manganese oxides, exhibit a volume‐changing redox reaction, rendering them an electrochemical actuation behavior. Also, due to their turbostratic crystal structures, they typically exhibit light‐driven actuation due to water deintercalation from the crystal structure induced by light. Compared with other actuating materials, these oxides/hydroxides actuate with high stress and strain at fast rates, under very low stimuli requirements. Furthermore, they are easily printable on different substrates, thus allowing flexible robots with demodularized muscle‐skeletal designs to be made. A series of oxides and hydroxides with turbostratic crystal structures are high‐performing actuating materials responsive to electrochemical, light, and other stimuli. Compared with other actuating materials, these materials exhibit high actuating stress and strain, at fast rates and under low stimuli requirements. They are also easily printable on different substrates for making flexible insect‐scale robots with demodularized muscle‐skeletal construction.