Design, synthesis and characterization of structured particles for chemical robots
Chemical robots are in principle artificial cells, with the exception of the ability to evolve and self-replicate. The main components of such a synthetic cell are (i) a “body” (shell) that defines properties such a size, shape, hardness and should facilitate the exchange of molecules with the environment similarly as a cell membrane, (ii) the internal space with compartments which should process absorbed molecules and release or accumulate products of chemical reactions. Chemical robots should also have the ability to move either passively or actively in the surrounding medium, and to adhere to target substrates or objects. Chemical robots may be used for targeted drug delivery, recovery of valuable chemicals from dilute resources, environmental clean-up, as smart diagnostic devices, or other applications.
The present thesis focuses on the description of basic requirements for particles that should serve as the outer bodies or internal compartments in such robots. Chemical robots are compared with living cells, their properties such as size, shape and surface characteristics are discussed. The chemotactic activity of both biological and artificial object, as well as their adhesion and interactions during mutual contact are reviewed.
In the experimental part, composite polymer/nanoparticle microcapsules were designed, synthesized and characterized in detail. A temperature-sensitive polymer poly-N-isopropylacrylamide (PNIPAM) with a reversible volume response to external stimuli was chosen as a suitable material, hence the composite PNIPAM/silica and PNIPAM/Fe3O4 microcapsules were prepared. The presence of silica nanoparticles on the surface makes it possible to attach further functionality such as ligands for specific adhesion. Owing to the presence of iron oxide nanoparticles, it is possible to induce a macroscopic volume change of the capsules as well as their hydrophobic/hydrophilic properties remotely by exposing them to an external alternating magnetic field in the radiofrequency range (400 kHz).
The methods for chemical and physical characterization of chemical robots, which are essential tools for successful chemical robots fabrication, are also summarized and several case studies where these methods were used are shown.