Reactive molecular robotics: toward molecular cybernetics based on artificial metabolism

Abstract Reactive architectures, robotic systems that directly couple sensory inputs to motor outputs, have enabled building dynamic and adaptive behaviors in mechanical robots. Extending this paradigm to molecular robotics could allow further autonomous and responsive functionalities with lifelike characteristics built from the nanoscale. Here, we introduce the concept of Reactive Molecular Robotics (RMR), a framework in which dissipative molecular processes are regulated by external cues to achieve dynamic behavior. As a first step toward realizing this goal, we implemented light-induced directional locomotion of slime-type molecular robots powered by artificial metabolism. Using 3-Cyanovinylcarbazole nucleoside ( $$^{\textrm{CNV}}$$ K), a reversible photocrosslinker, the light-triggered structure generation mechanism of artificial metabolism has been implemented. As an initial, open-loop proof of concept, quasi-phototactic behavior is demonstrated through pre-irradiation of UV light with specific wavelengths to the generation mix of slime-type molecular robots. The reaction results in directional locomotion within a Y-shaped microfluidic device towards the channel with the generation-triggered side, representing an analogy to Braitenberg vehicle 2a motion based on the molecular-level control of the metabolic pathway. The proposed RMR framework provides an architectural basis for developing molecular robots toward higher-order adaptability and lays the groundwork for creating adaptive and dynamically regulated forms of synthetic matter.