Enhancing the Light-Induced Actuation of Nickel Oxyhydroxide by Aluminum Doping

Material-based actuators for developing miniature robotic systems is an emerging field of interest. Transition metal oxides/hydroxides (TMOs) are introduced for light-induced actuation based on their effective photothermal mechanism of water deintercalation from their turbostratic crystal structures. Previous studies have demonstrated doping different metal ions into TMOs can make the crystals more turbostratic (more disordered), which can be utilized to enhance the light-induced actuation is hypothesized. This work studies the effectiveness of aluminum (Al) doping in increasing the turbostraticity and hence actuation performance of TMO of nickel oxyhydroxide (NiOOH). Scanning electron microscopy indicates that Al-doping can be made into the NiOOH directly by soaking into aluminum sulfate solution without forming surface structures or agglomerated precipitates, and transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis shows that a more turbostratic phase structure and better hydration capability are acquired. This Al-doped NiOOH demonstrates enhanced actuation performance by approximate to 30% compared to the undoped counterpart.