Development of 2D MOF-Based Microrobots under Annealing Treatment and Their Biomedical Application

Magnetic microrobots have potential applications in various fields of biomedicine, such as minimally invasive surgery, targeted diagnosis, and treatment. In this work, the crystalline properties of ZnO on two-dimensional (2D) magnetic microrobot precursors were tuned by annealing at different temperatures. On this basis, zeolite-imidazole framework 8 (ZIF-8) was then synthesized on the precursor surface. Through conventional characterization studies, the results showed that the precursor tuned by annealing treatment (from 350 to 500 °C) could be used for the synthesis of ZIF-8 on microrobots with specific two-dimensional structures, thus becoming metal–organic framework (MOF)-based microrobot. Also, the optimal temperature was around 410 °C, which contributed to surface roughening of the precursor and provided more reaction sites for the growth of cubic ZIF-8 particles. The MOF-based 2D microrobots were tested for their locomotive capabilities using a three-dimensional (3D) Helmholtz coil system and were able to reach a maximum forward swimming speed of 107 μm/s under a 12 Hz rotating magnetic field of 4 mT. The steerability of the microrobots was validated through successful navigation inside a microfluidic channel. The high drug loading efficiency of the MOF-based microrobots was validated using a drug loading test. In summary, MOF-based microrobots have high drug loading capacity and strong locomotive capabilities, which suggest a strong potential for in vivo biomedical applications in hard-to-reach areas of the human body.