Plasmonic-Enhanced Graphene Oxide-Based Aquatic Robot for Target Cargo Delivery.

The design and fabrication of light-actuated robots that can perform selective motions and targeted cargo delivery have attracted increasing interest in various fields. However, these robots' high-speed locomotion, precise direction control, and efficient actuation ability remain big challenges because of the relatively low photothermal efficiency, especially in the aquatic environment. This work proposes a plasmonic-enhanced graphene oxide (GO)-gold nanorod (Au NR)/calcium alginate (Ca-alginate) aquatic robot. The proposed robot design includes an independent power module (GO-Au NR layer) and a microscale cargo-loaded module (Ca-alginate layer). The plasmonic effect of Au NRs greatly improves the heat transfer efficiency, which in turn increases the temperature variation up to three times during the actuating process. This situation leads to a high traveling speed of the robot up to ∼35 mm/s. Benefiting from the high light-to-work efficiency, the position and posture of the proposed robot have good control in the aquatic environment. The robot is capable of programmable trajectory following, multirobot gathering, separation, and cooperation, providing an efficient solution for cargo delivery. Moreover, after releasing the cargo-loaded module to the target location, the power module can be easily actuated for collection, avoiding the potential side effects from the residual photothermal particles in conventional methods. The plasmonic-enhanced photothermal mechanism and independent module design offer a strategy for light-actuated aquatic robot development and would bring opportunities to further develop biomedical applications.