Photothermally Modulated Magnetic Nanochains as Swarm Nanorobotics for Microreaction Control

The intensification of microreactions is important for biological and chemical reactions with microliter volumes as reaction units, including microliter bioassay or protein synthesis. At the micro/nanoscale, the fluid flow is usually located in the laminar region, making the interaction between different layers of material more difficult. In the absence of external intervention, the microscale transport of substances is dominated by passive diffusion, leading to a lower mixing efficiency and longer reaction times, which is disadvantageous for reactions requiring timeliness, such as microliter bioassays. Therefore, the intensification of microreactions is essential. Here, a dual magnetic–photothermal microreaction control platform was created, based on the cooperative roles of a close-loop photothermally controlled magnetically active nanoswarm (PMANS) as a nanostir for quick fluid mixing and as a nanoheating agent for the reaction solution. The platform was demonstrated to be enhanced for microreactions by using the glucose oxidase and horseradish peroxidase cascade and cell-free synthetic superfolder green fluorescent protein reactions, which are typical in the fields of diagnostic testing and biomanufacturing, respectively. The rotational motion of the PMANS is controlled by the magnetic field to achieve efficient and homogeneous mixing of fluids at the microscale. On the other hand, the PMANS is used to heat the reaction system through light control. The construction of a dual magnetic–temperature control platform provided a new strategy for microreaction enhancement that was convenient, controllable, and broadly applicable. This control platform has great potential for microscale reaction enhancement in detection, sensing, catalysis, and synthesis.