Magnetically Controlled Pollen Microrobots for Underwater Bubble Manipulation-Adhesion, Transport, and...

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.