Illumination-oriented and thickness-dependent photomechanical bilayer actuators realized by graphene-nanoplatelets

Photomechanical bilayer actuators, constituted by PDMS/GNPs thin layer and PDMS thin layer, are presented. Due to the photothermal effect of GNPs and differences in CTE of the two layers caused by the GNPs existed in PDMS/GNPs thin layer; the bilayer actuator can display photomechanical bending under nIR light irradiation. And it is interesting to notice that the bilayer actuators show a two-step photomechanical bending process when the nIR light is incident from the PDMS/GNPs thin layer while one-step photomechanical bending process when from the PDMS thin layer, which is different from the process commonly observed in thermal bilayer and bimorph actuators. According to preliminary analysis, it is revealed that the photomechanical two-step bending is the results of temperature gradient effect and thermal bilayer effect, while the one-step photomechanical bending process only caused by thermal bilayer effect. Meanwhile, the photomechanical bendings are both positively correlated with light intensities. By adjusting the rotation speed in spinning coating, various bilayer actuators with different thickness of PDMS thin layer were fabricated and tested. The photomechanical deflections decreased with the augment of rotation speed. In addition, the realization of micromachines with our proposed bilayer actuators was demonstrated.