The cube-shaped hematite microrobot for biomedical application

This work reports a method for microblocks and impurities sweep using a kind of cube-shaped hematite microrobot (CHM) with a side length of about 2 ?m under the vision-guided magnetic driving (VMD) system. CHM was manipulated by the VMD system in two motion modes: rolling and tumbling in a low Reynolds number (Re) environment. The CHM can go up to the peak velocity of 20.8 ?m/s (10.4 body lengths/s) in rolling mode under a 100 Hz and 10 mT rotating magnetic field and climb over barriers capable of meeting complex environment requirements. CHM was capable of tracking automatically generated predefined trajectories accurately and getting out from a micromaze by modulating intensity, frequency, and direction of magnetic field. The CHMs had two collective states: rotating CHMs pairs in rotating magnetic driving field and rows of CHMs in a conical rotating magnetic driving field. A strategy is proposed to transfer rotating CHMs pairs to target areas efficiently by magnetic field. When encountered microblock at the entrance of microchannel, single CHM can trap, transport and release the microblock with about 200 times of volume. Finally, rows of CHMs were generated for sweeping impurity tasks in microchannel. The experimental results demonstrate that the CHM has superior potential for biomedical sweep task in complex curved microchannels, similar to the blood vessels.