Synthetic micro-/nanomotors (MNMs) are capable of performing self-propelled motion in fluids through harvesting different types of energies into mechanical movement, with potential applications in biomedicine and other fields. To address the challenges in these applications, a promising strategy that combines controlled assembly (bottom-up approaches) with top-down approaches for engineering autonomous, multifunctionalized MNMs is under investigation, beginning in 2012. These MNMs, derived from layer-by-layer assembly or molecular self-assembly, display the advantages of: i) mass production, ii) response to the external stimuli, and iii) access to multifunctionality, biocompatibility, and biodegradability. The advance on how to integrate diverse functional components into different architectures based on controlled assemblies, to realize controlled fabrication, motion control (including the movement speed, direction, and state), and biomedical applications of MNMs, directed by the concept of nanoarchitectonics, are highlighted here. The remaining challenges and future research directions are also discussed.

We report a self-propelled Janus silica micromotor as a motion-based analytical method for achieving fast target separation of polyelectrolyte microcapsules, enriching different charged organics with low molecular weights in water. The self-propelled Janus silica micromotor catalytically decomposes a hydrogen peroxide fuel and moves along the direction of the catalyst face at a speed of 126.3 μm s⁻¹. Biotin-functionalized Janus micromotors can specifically capture and rapidly transport streptavidin-modified polyelectrolyte multilayer capsules, which could effectively enrich and separate different charged organics in water. The interior of the polyelectrolyte multilayer microcapsules were filled with a strong charged polyelectrolyte, and thus a Donnan equilibrium is favorable between the inner solution within the capsules and the bulk solution to entrap oppositely charged organics in water. The integration of these self-propelled Janus silica micromotors and polyelectrolyte multilayer capsules into a lab-on-chip device that enables the separation and analysis of charged organics could be attractive for a diverse range of applications.

The synthesis of an innovative self-propelled Janus nanomotor with a diameter of about 75 nm that can be used as a drug carrier is described. The Janus nanomotor is based on mesoporous silica nanoparticles (MSNs) with chromium/platinum metallic caps and propelled by decomposing hydrogen peroxide to generate oxygen as a driving force with speeds up to 20.2 μm s⁻¹ (about 267 body lengths per second). The diffusion coefficient (D) of nanomotors with different H₂O₂ concentrations is calculated by tracking the movement of individual particles recorded by means of a self-assembled fluorescence microscope and is significantly larger than free Brownian motion. The traction of a single Janus MSN nanomotor is estimated to be about 13.47×10⁻¹⁵ N. Finally, intracellular localization and drug release in vitro shows that the amount of Janus MSN nanomotors entering the cells is more than MSNs with same culture time and particle concentrations, meanwhile anticancer drug doxorubicin hydrochloride loaded in Janus MSNs can be slowly released by biodegradation of lipid bilayers in cells.