Multimodal propulsion of synthetic microbots

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The recent quest for miniaturization has inspired researchers to design and develop micro or nanorobots suitable for multifarious applications. The present thesis reports the fabrication of a host of micromotors composed of iron nanoparticles (FeNPs) aggregates, FeNPs coated on polymeric materials, paper, and agglomerates of pollutant carbon soot. These fabricated micromotors were employed for pH sensing, cargo transport, hydrogen generation and water detoxification applications. The Chapter 1 introduces the general introduction and basic concepts related to the self-propulsion of synthetic micro/nanoswimmers. The Chapter 2 reports a controlled migration of an iron nanoparticle (FeNP) coated polymer micromotor. The self-propulsion owing to the asymmetric catalytic decomposition of peroxide fuel was directed through a pH gradient imposed across the motor-surface, while the magnetic field induced an external control on the movement and the speed of the motor. The Chapter 3 demonstrates the design and development of a self-propelling ferrobot composed of a collection of iron nanoparticles (FeNPs). While the propulsive thrust required for the chemotactic migration of the ferrobots was generated through the ejection of hydrogen bubbles due to the reaction of aqueous formic acid (FA) with FeNP clusters on the motor surface, presence of ferromagnetic FeNPs assured “on-the-fly” remote guidance using an external magnetic field. The experiments uncovered the potential of the proposed ferrobots not only for the on-demand power supply to the portable devices but also as a single-step commercial process to produce pure hydrogen under ambient condition and devoid of greenhouse gas emission. In the Chapter 4, the self-propulsion of paper-based microjets, namely paperbots has been explored, which has multimodal chemical and magnetic controls on the motion. The Chapter 5 shows fabrication of multifunctional chemically-powered carbon soot-based microbots, namely CARBOts, by heterogeneous deposition of catalytic platinum (Pt) and magnetic nickel (Ni) nanofilms on the airborne contaminant carbon soot (CS) for environmental remediation. These magneto-catalytic CARBOts demonstrated efficient catalytic degradation of methylene blue (MB) dye in the presence of 10% (v/v) H2O2 fuel under ambient conditions. The intrinsic oleophillic nature of the CARBOts facilitated successful oil-motor interaction, which led to efficient on-the-fly capturing of oil droplets. The Chapter 6 concludes with the thesis summary and a concise discussion on the future prospects of micromotors discussed in this thesis work.
Supervisors: Dipankar Bandyopadhyay and Tapas Kumar Mandal