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Urso M, Ussia M, Peng X, Oral CM, Pumera M. Reconfigurable self-assembly of photocatalytic magnetic microrobots for water purification. Nat Commun 2023; 14:6969. [PMID: 37914692 PMCID: PMC10620202 DOI: 10.1038/s41467-023-42674-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 10/18/2023] [Indexed: 11/03/2023] Open
Abstract
The development of artificial small-scale robotic swarms with nature-mimicking collective behaviors represents the frontier of research in robotics. While microrobot swarming under magnetic manipulation has been extensively explored, light-induced self-organization of micro- and nanorobots is still challenging. This study demonstrates the interaction-controlled, reconfigurable, reversible, and active self-assembly of TiO2/α-Fe2O3 microrobots, consisting of peanut-shaped α-Fe2O3 (hematite) microparticles synthesized by a hydrothermal method and covered with a thin layer of TiO2 by atomic layer deposition (ALD). Due to their photocatalytic and ferromagnetic properties, microrobots autonomously move in water under light irradiation, while a magnetic field precisely controls their direction. In the presence of H2O2 fuel, concentration gradients around the illuminated microrobots result in mutual attraction by phoretic interactions, inducing their spontaneous organization into self-propelled clusters. In the dark, clusters reversibly reconfigure into microchains where microrobots are aligned due to magnetic dipole-dipole interactions. Microrobots' active motion and photocatalytic properties were investigated for water remediation from pesticides, obtaining the rapid degradation of the extensively used, persistent, and hazardous herbicide 2,4-Dichlorophenoxyacetic acid (2,4D). This study potentially impacts the realization of future intelligent adaptive metamachines and the application of light-powered self-propelled micro- and nanomotors toward the degradation of persistent organic pollutants (POPs) or micro- and nanoplastics.
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Affiliation(s)
- Mario Urso
- Future Energy and Innovation Laboratory, Central European Institute of Technology, Brno University of Technology, Purkyňova 123, 61200, Brno, Czech Republic
| | - Martina Ussia
- Future Energy and Innovation Laboratory, Central European Institute of Technology, Brno University of Technology, Purkyňova 123, 61200, Brno, Czech Republic
| | - Xia Peng
- Future Energy and Innovation Laboratory, Central European Institute of Technology, Brno University of Technology, Purkyňova 123, 61200, Brno, Czech Republic
| | - Cagatay M Oral
- Future Energy and Innovation Laboratory, Central European Institute of Technology, Brno University of Technology, Purkyňova 123, 61200, Brno, Czech Republic
| | - Martin Pumera
- Future Energy and Innovation Laboratory, Central European Institute of Technology, Brno University of Technology, Purkyňova 123, 61200, Brno, Czech Republic.
- Advanced Nanorobots & Multiscale Robotics Laboratory, Faculty of Electrical Engineering and Computer Science, VSB-Technical University of Ostrava, 17. listopadu 2172/15, 70800, Ostrava, Czech Republic.
- Department of Medical Research, China Medical University Hospital, China Medical University, Hsueh-Shih Road 91, 40402, Taichung, Taiwan.
- Department of Chemical and Biomolecular Engineering, Yonsei University, Yonsei-ro 50, Seodaemun-gu, 03722, Seoul, Republic of Korea.
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Popescu MN, Gáspár S. Analyte Sensing with Catalytic Micromotors. BIOSENSORS 2022; 13:45. [PMID: 36671880 PMCID: PMC9856142 DOI: 10.3390/bios13010045] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 12/21/2022] [Accepted: 12/23/2022] [Indexed: 06/17/2023]
Abstract
Catalytic micromotors can be used to detect molecules of interest in several ways. The straightforward approach is to use such motors as sensors of their "fuel" (i.e., of the species consumed for self-propulsion). Another way is in the detection of species which are not fuel but still modulate the catalytic processes facilitating self-propulsion. Both of these require analysis of the motion of the micromotors because the speed (or the diffusion coefficient) of the micromotors is the analytical signal. Alternatively, catalytic micromotors can be used as the means to enhance mass transport, and thus increase the probability of specific recognition events in the sample. This latter approach is based on "classic" (e.g., electrochemical) analytical signals and does not require an analysis of the motion of the micromotors. Together with a discussion of the current limitations faced by sensing concepts based on the speed (or diffusion coefficient) of catalytic micromotors, we review the findings of the studies devoted to the analytical performances of catalytic micromotor sensors. We conclude that the qualitative (rather than quantitative) analysis of small samples, in resource poor environments, is the most promising niche for the catalytic micromotors in analytical chemistry.
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Affiliation(s)
- Mihail N. Popescu
- Física Teórica, Universidad de Sevilla, Apdo. 1065, E-41080 Sevilla, Spain
| | - Szilveszter Gáspár
- International Centre of Biodynamics, 1B Intrarea Portocalelor, 060101 Bucharest, Romania
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Gomez-Solano JR, Rodríguez RF, Salinas-Rodríguez E. Nonequilibrium dynamical structure factor of a dilute suspension of active particles in a viscoelastic fluid. Phys Rev E 2022; 106:054602. [PMID: 36559383 DOI: 10.1103/physreve.106.054602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 10/11/2022] [Indexed: 11/06/2022]
Abstract
In this work we investigate the dynamics of the number-density fluctuations of a dilute suspension of active particles in a linear viscoelastic fluid. We propose a model for the frequency-dependent diffusion coefficient of the active particles which captures the effect of rotational diffusion on the persistence of their self-propelled motion and the viscoelasticity of the medium. Using fluctuating hydrodynamics, the linearized equations for the active suspension are derived, from which we calculate its dynamic structure factor and the corresponding intermediate scattering function. For a Maxwell-type rheological model, we find an intricate dependence of these functions on the parameters that characterize the viscoelasticity of the solvent and the activity of the particles, which can significantly deviate from those of an inert suspension of passive particles and of an active suspension in a Newtonian solvent. In particular, in some regions of the parameter space we uncover the emergence of oscillations in the intermediate scattering function at certain wave numbers which represent the hallmark of the nonequilibrium particle activity in the dynamical structure of the suspension and also encode the viscoelastic properties of the medium.
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Affiliation(s)
- Juan Ruben Gomez-Solano
- Instituto de Física, Universidad Nacional Autónoma de México, Ciudad de México, Código Postal 04510, Mexico
| | - Rosalío F Rodríguez
- Instituto de Física, Universidad Nacional Autónoma de México, Ciudad de México, Código Postal 04510, Mexico.,FENOMEC, Universidad Nacional Autónoma de México, Apdo. Postal 20-726, 01000 Ciudad de México, Mexico
| | - Elizabeth Salinas-Rodríguez
- Departamento I. P. H., Universidad Autónoma Metropolitana, Iztapalapa, Apdo. Postal 55-534, 09340 Ciudad de México, Mexico
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Möller N, Liebchen B, Palberg T. Shaping the gradients driving phoretic micro-swimmers: influence of swimming speed, budget of carbonic acid and environment. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:41. [PMID: 33759011 PMCID: PMC7987694 DOI: 10.1140/epje/s10189-021-00026-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 01/22/2021] [Indexed: 05/07/2023]
Abstract
pH gradient-driven modular micro-swimmers are investigated as a model for a large variety of quasi-two-dimensional chemi-phoretic self-propelled entities. Using three-channel micro-photometry, we obtain a precise large field mapping of pH at a spatial resolution of a few microns and a pH resolution of [Formula: see text] units for swimmers of different velocities propelling on two differently charged substrates. We model our results in terms of solutions of the three-dimensional advection-diffusion equation for a 1:1 electrolyte, i.e. carbonic acid, which is produced by ion exchange and consumed by equilibration with dissolved [Formula: see text]. We demonstrate the dependence of gradient shape and steepness on swimmer speed, diffusivity of chemicals, as well as the fuel budget. Moreover, we experimentally observe a subtle, but significant feedback of the swimmer's immediate environment in terms of a substrate charge-mediated solvent convection. We discuss our findings in view of different recent results from other micro-fluidic or active matter investigations. We anticipate that they are relevant for quantitative modelling and targeted applications of diffusio-phoretic flows in general and artificial micro-swimmers in particular.
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Affiliation(s)
- Nadir Möller
- Institute of Condensed Matter Physics, Johannes Gutenberg Universität, Staudinger Weg 7, 55128, Mainz, Germany.
- Max Planck Graduade Center, Institute of Physics, Johannes Gutenberg Universität, Staudinger Weg 7, 55128, Mainz, Germany.
| | - Benno Liebchen
- Institute for Condensed Matter Physics, Technische Universität Darmstadt, Hochschulstr. 8, 64289, Darmstadt, Germany
| | - Thomas Palberg
- Institute of Condensed Matter Physics, Johannes Gutenberg Universität, Staudinger Weg 7, 55128, Mainz, Germany
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