Magnetically Controlled Pollen Microrobots for Underwater Bubble Manipulation–Adhesion, Transport, and Photocontrolled Release

The traditional approach has significant limitations in designing and manufacturing high-performance micro-nanorobots with complex three-dimensional structures and response characteristics at the micro-nanoscale, making it difficult to meet practical demands. The ingenious utilization of the structural characteristics of natural pollen is expected to solve this difficulty. Sunflower pollen has a spiky spherical structure. It is expected to be used for the preparation of high-performance microrobots. A magnetically responsive bubble-controlled micro-nanorobot (MNR) platform with natural sunflower pollen as the “skeleton” has been developed. Its micro/nano composite multilevel surface morphology can load magnetic nanoparticles and achieve high hydrophilicity/hydrophobicity. The spherical profile and an average particle size of 30 μm endow it with high passability. The excellent magnetic/optical response and hydrophilicity of MNR enable the capture and release of 5–100 μL bubbles in complex environments. A precise bubble fixed-point release scheme based on the excellent photothermal properties of MNR is revealed. The loading of photothermal particles through simulation calculation enables MNR to heat up to 141.9 °C within 7 s and achieve rapid bubble release within 100 μs. The rapid merging of bubbles can be achieved at 50 μs in the gas–liquid simulation reaction. It passed the “maze test”. It shows good biocompatibility. The cell mortality rate of SP, SPC, and MNR cells cocultured for 24 h is only 7.8–11.2%. This reveals the possibility of application in organoid microchips.