**Figure 24.**

*Categories of biomedical applications of micro/nanomotors, including sensing and isolation, drug delivery, nanosurgery, biomedical imaging. Copyright 2014, RSC Publications.*

#### **Figure 25.**

*(A) A catalytic nanojet drilling into an immobilized cancer cell. (B) SEM image of a magnetic microtube drilling into pig liver tissue. (C) Hole after removing the microtube. (D) Nanorods inside living HeLa cells: (a) multiple nanorods inside a HeLa cell, (b) subcellular structures (a few indicated by arrows) interacting with active acoustic motors inside a HeLa cell, and (c) two vesicular structures in a HeLa cell containing many active but crowded acoustic motors, respectively, can be seen. (E) Preparation and propulsion of perfluorocarbonloaded microbullets (a), Computer-created diagram (b), and images of a microbullet penetrating a tissue after an ultrasound pulse (c and d), respectively. Copyright 2012, ACS Publications. Copyright 2013, RSC Publications. Copyright 2014, Wiley Online Library. Copyright 2012, Wiley Online Library.*

friendly sources of movement are urgently required to replace H2O2. Magnetic trigger can be used as an alternative to the motion. Conical microtubes powered by an external rotating magnetic field were placed onto liver tissue and drilled into it for long periods, as shown in **Figure 25B** [69]. After releasing the microtube from the biomaterial, a micrometer-sized hole was observed by SEM, as shown in

*Catalytic Micro/Nanomotors: Propulsion Mechanisms, Fabrication, Control, and Applications DOI: http://dx.doi.org/10.5772/intechopen.90456*

**Figure 25C** [69]. Ultrasonic waves can also generate the propulsion of micro-/ nanomotors, as shown in **Figure 25D** and **E**) [70, 71]. Bio-functionalized nanowires propelled by ultrasound have been applied for bio-sensing, and the first results of magnetic steering toward cells have been studied. Mallouk et al. demonstrated the internalization of a nanowire-based motor inside living cells, as shown in **Figure 25D**. Developing biocompatible materials and fuels for artificial micro-/ nanomotors or the use of noninvasive external triggered motors may pave the way for biomedical applications of micro-/nanomotors in the near future [72–80].
