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Boymelgreen A, Kunti G, García-Sánchez P, Yossifon G. The influence of frequency and gravity on the orientation of active metallo-dielectric Janus particles translating under a uniform applied alternating-current electric field. SOFT MATTER 2024; 20:4143-4151. [PMID: 38738604 DOI: 10.1039/d3sm01640d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
Theoretical and numerical models of active Janus particles commonly assume that the metallo-dielectric interface is parallel to the driving applied electric field. However, our experimental observations indicate that the equilibrium angle of orientation of electrokinetically driven Janus particles varies as a function of the frequency and voltage of the applied electric field. Here, we quantify the variation of the orientation with respect to the electric field and demonstrate that the equilibrium position represents the interplay between gravitational, electrostatic and electrohydrodynamic torques. The latter two categories are functions of the applied field (frequency, voltage) as well as the height of the particle above the substrate. Maximum departure from the alignment with the electric field occurs at low frequencies characteristic of induced-charge electrophoresis and at low voltages where gravity dominates the electrostatic and electrohydrodynamic torques. The departure of the interface from alignment with the electric field is shown to decrease particle mobility through comparison of freely suspended Janus particles subject only to electrical forcing and magnetized Janus particles in which magnetic torque is used to align the interface with the electric field. Consideration of the role of gravitational torque and particle-wall interactions could account for some discrepancies between theory, numerics and experiment in active matter systems.
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Affiliation(s)
- Alicia Boymelgreen
- Department of Mechanical and Materials Engineering, Florida International University, Miami, Florida, 33174, USA.
| | - Golak Kunti
- Faculty of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, 110016, India
- Faculty of Mechanical Engineering, Technion - Israel Institute of Technology, Technion City, Haifa, 3200003, Israel
| | - Pablo García-Sánchez
- Departamento de Electrónica y Electromagnetismo, Facultad de Física, Universidad de Sevilla, Avda. Reina Mercedes, Sevilla, Spain
| | - Gilad Yossifon
- School of Mechanical Engineering, Tel Aviv University, Ramat Aviv 6997801, Israel
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2
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Flores-Mena JE, García-Sánchez P, Ramos A. Induced-charge electrophoresis of a tilted metal nanowire near an insulating wall. Phys Rev E 2024; 109:045109. [PMID: 38755876 DOI: 10.1103/physreve.109.045109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 04/11/2024] [Indexed: 05/18/2024]
Abstract
Electric fields are commonly used to control the orientation and motion of microscopic metal particles in aqueous suspensions. For example, metallodielectric Janus spheres are propelled by the induced-charge electro-osmotic flow occurring on their metallic side, the most common case in electrokinetics of exploiting symmetry breaking of surface properties for achieving net particle motion. In this work, we demonstrate that a homogeneous metal rod can translate parallel to a dielectric wall as a result of the hydrodynamic wall-particle interaction arising from the induced-charge electro-osmosis on the rod surface. The applied electric field could be either dc or low-frequency ac. The only requirement for a nonvanishing particle velocity is that the axis of the rod be inclined with respect to the wall, i.e., it cannot be neither parallel nor perpendicular. We show numerical results of the rod velocity as a function of rod orientation and distance to the wall. The maximum particle velocity is found for an orientation of between ∼30^{∘} and ∼50^{∘}, depending on the position and aspect ratio of the cylinder. Particle velocities of up to tens of µm/s are predicted for typical conditions in electrokinetic experiments.
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Affiliation(s)
- Jose Eladio Flores-Mena
- Facultad de Ciencias de la Electrónica, Benemérita Universidad Autónoma de Puebla, Av. San Claudio y 18 Sur, San Manuel, CU. FCE2, 72570 Puebla, Mexico
| | - Pablo García-Sánchez
- Departamento de Electrónica y Electromagnetismo, Facultad de Física, Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012 Sevilla, Spain
| | - Antonio Ramos
- Departamento de Electrónica y Electromagnetismo, Facultad de Física, Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012 Sevilla, Spain
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3
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Kichatov B, Korshunov A, Sudakov V, Gubernov V, Golubkov A, Kolobov A, Kiverin A, Chikishev L. Motion of magnetic motors across liquid-liquid interface. J Colloid Interface Sci 2023; 652:1456-1466. [PMID: 37659314 DOI: 10.1016/j.jcis.2023.08.138] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 08/01/2023] [Accepted: 08/21/2023] [Indexed: 09/04/2023]
Abstract
HYPOTHESIS In a number of applications related to chemical engineering and drug delivery, magnetic nanoparticles should move through a liquid-liquid interface in the presence of surfactant molecules. However, due to the action of capillary forces, this is not always possible. The mechanism of particle motion through the interface essentially depends on the intensity of the Marangoni flow, which is induced on the interface during its deformation. EXPERIMENTS In this paper we study the motion of nanoparticles Fe3O4 through the water-tridecane interface under the action of a nonuniform magnetic field when using different surfactants. FINDINGS If the linear size of the magnetic motor turns out to be less than a certain critical value, then it is not able to move between phases due to the action of capillary forces on the interface. Depending on the type and concentration of the surfactant used, various mechanisms for the motor motion through the liquid-liquid interface can be carried out. In one of them, a liquid phase is transferred through the interface along with a movable motor, while in the other, it is not.
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Affiliation(s)
- Boris Kichatov
- Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow, Russia.
| | - Alexey Korshunov
- Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow, Russia
| | - Vladimir Sudakov
- Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow, Russia
| | - Vladimir Gubernov
- Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow, Russia
| | - Alexandr Golubkov
- Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow, Russia
| | - Andrey Kolobov
- Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow, Russia
| | - Alexey Kiverin
- Joint Institute for High Temperatures, Russian Academy of Sciences, 125412 Moscow, Russia
| | - Leonid Chikishev
- Kutateladze Institute of Thermophysics, Russian Academy of Sciences, 630090 Novosibirsk, Russia
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Lee JG, Thome CP, Cruse ZA, Ganguly A, Gupta A, Shields CW. Magnetically locked Janus particle clusters with orientation-dependent motion in AC electric fields. NANOSCALE 2023; 15:16268-16276. [PMID: 37800377 PMCID: PMC10598768 DOI: 10.1039/d3nr03744d] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/07/2023]
Abstract
Active particles, or micromotors, locally dissipate energy to drive locomotion at small length scales. The type of trajectory is generally fixed and dictated by the geometry and composition of the particle, which can be challenging to tune using conventional fabrication procedures. Here, we report a simple, bottom-up method to magnetically assemble gold-coated polystyrene Janus particles into "locked" clusters that display diverse trajectories when stimulated by AC electric fields. The orientation of particles within each cluster gives rise to distinct modes of locomotion, including translational, rotational, trochoidal, helical, and orbital. We model this system using a simplified rigid beads model and demonstrate qualitative agreement between the predicted and experimentally observed cluster trajectories. Overall, this system provides a facile means to scalably create micromotors with a range of well-defined motions from discrete building blocks.
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Affiliation(s)
- Jin Gyun Lee
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO 80303, USA.
| | - Cooper P Thome
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO 80303, USA.
| | - Zoe A Cruse
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO 80303, USA.
| | - Arkava Ganguly
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO 80303, USA.
| | - Ankur Gupta
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO 80303, USA.
| | - C Wyatt Shields
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO 80303, USA.
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Katzmeier F, Simmel FC. Microrobots powered by concentration polarization electrophoresis (CPEP). Nat Commun 2023; 14:6247. [PMID: 37802992 PMCID: PMC10558450 DOI: 10.1038/s41467-023-41923-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 09/21/2023] [Indexed: 10/08/2023] Open
Abstract
Second-order electrokinetic flow around colloidal particles caused by concentration polarization electro-osmosis (CPEO) can result in a phoretic motion of asymmetric particle dimers in a homogeneous AC electrical field, which we refer to as concentration polarization electro-phoresis (CPEP). To demonstrate this actuation mechanism, we created particle dimers from micron-sized silica spheres with sizes 1.0 μm and 2.1 μm by connecting them with DNA linker molecules. The dimers can be steered along arbitrarily chosen paths within a 2D plane by controlling the orientation of the AC electric field in a fluidic chamber with the joystick of a gamepad. Further utilizing induced dipole-dipole interactions, we demonstrate that particle dimers can be used to controllably pick up monomeric particles and release them at any desired position, and also to assemble several particles into groups. Systematic experiments exploring the dependence of the dimer migration speed on the electric field strength, frequency, and buffer composition align with the theoretical framework of CPEO and provide parameter ranges for the operation of our microrobots. Furthermore, experiments with a variety of asymmetric particles, such as fragmented ceramic, borosilicate glass, acrylic glass, agarose gel, and ground coffee particles, as well as yeast cells, demonstrate that CPEP is a generic phenomenon that can be expected for all charged dielectric particles.
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Affiliation(s)
- Florian Katzmeier
- Department of Bioscience, TUM School of Natural Sciences, Technical University Munich, D-85748, Garching, Germany
| | - Friedrich C Simmel
- Department of Bioscience, TUM School of Natural Sciences, Technical University Munich, D-85748, Garching, Germany.
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Das SS, Yossifon G. Optoelectronic Trajectory Reconfiguration and Directed Self-Assembly of Self-Propelling Electrically Powered Active Particles. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2206183. [PMID: 37069767 DOI: 10.1002/advs.202206183] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2022] [Revised: 01/25/2023] [Indexed: 06/04/2023]
Abstract
Self-propelling active particles are an exciting and interdisciplinary emerging area of research with projected biomedical and environmental applications. Due to their autonomous motion, control over these active particles that are free to travel along individual trajectories, is challenging. This work uses optically patterned electrodes on a photoconductive substrate using a digital micromirror device (DMD) to dynamically control the region of movement of self-propelling particles (i.e., metallo-dielectric Janus particles (JPs)). This extends previous studies where only a passive micromotor is optoelectronically manipulated with a translocating optical pattern that illuminates the particle. In contrast, the current system uses the optically patterned electrode merely to define the region within which the JPs moved autonomously. Interestingly, the JPs avoid crossing the optical region's edge, which enables constraint of the area of motion and to dynamically shape the JP trajectory. Using the DMD system to simultaneously manipulate several JPs enables to self-assemble the JPs into stable active structures (JPs ring) with precise control over the number of participating JPs and passive particles. Since the optoelectronic system is amenable to closed-loop operation using real-time image analysis, it enables exploitation of these active particles as active microrobots that can be operated in a programmable and parallelized manner.
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Affiliation(s)
- Sankha Shuvra Das
- School of Mechanical Engineering, Tel-Aviv University, Tel-Aviv, 69978, Israel
| | - Gilad Yossifon
- School of Mechanical Engineering, Tel-Aviv University, Tel-Aviv, 69978, Israel
- Department of Biomedical Engineering, Tel-Aviv University, Tel-Aviv, 69978, Israel
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7
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Chen X, Chen X, Peng Y, Zhu L, Wang W. Dielectrophoretic Colloidal Levitation by Electrode Polarization in Oscillating Electric Fields. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:6932-6945. [PMID: 37148258 DOI: 10.1021/acs.langmuir.3c00759] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Controlled colloidal levitation is key to many applications. Recently, it was discovered that polymer microspheres were levitated to a few micrometers in aqueous solutions in alternating current (AC) electric fields. A few mechanisms have been proposed to explain this AC levitation such as electrohydrodynamic flows, asymmetric rectified electric fields, and aperiodic electrodiffusiophoresis. Here, we propose an alternative mechanism based on dielectrophoresis in a spatially inhomogeneous electric field gradient extending from the electrode surface micrometers into the bulk. This field gradient is derived from electrode polarization, where counterions accumulate near electrode surfaces. A dielectric microparticle is then levitated from the electrode surface to a height where the dielectrophoretic lift balances gravity. The dielectrophoretic levitation mechanism is supported by two numerical models. One model assumes point dipoles and solves for the Poisson-Nernst-Planck equations, while the second model incorporates a dielectric sphere of a realistic size and permittivity and uses the Maxwell-stress tensor formulation to solve for the electrical body force. In addition to proposing a plausible levitation mechanism, we further demonstrate that AC colloidal levitation can be used to move synthetic microswimmers to controlled heights. This study sheds light on understanding the dynamics of colloidal particles near an electrode and paves the way to using AC levitation to manipulate colloidal particles, active or passive.
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Affiliation(s)
- Xiaowen Chen
- Sauvage Laboratory for Smart Materials, School of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China
| | - Xi Chen
- Sauvage Laboratory for Smart Materials, School of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China
| | - Yixin Peng
- Sauvage Laboratory for Smart Materials, School of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China
| | - Lailai Zhu
- Department of Mechanical Engineering, National University of Singapore, Singapore 117575, Singapore
| | - Wei Wang
- Sauvage Laboratory for Smart Materials, School of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China
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8
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Thome C, Hoertdoerfer WS, Bendorf JR, Lee JG, Shields CW. Electrokinetic Active Particles for Motion-Based Biomolecule Detection. NANO LETTERS 2023; 23:2379-2387. [PMID: 36881680 PMCID: PMC10038089 DOI: 10.1021/acs.nanolett.3c00319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 02/23/2023] [Indexed: 06/18/2023]
Abstract
Detection of biomolecules is essential for patient diagnosis, disease management, and numerous other applications. Recently, nano- and microparticle-based detection has been explored for improving traditional assays by reducing required sample volumes and assay times as well as enhancing tunability. Among these approaches, active particle-based assays that couple particle motion to biomolecule concentration expand assay accessibility through simplified signal outputs. However, most of these approaches require secondary labeling, which complicates workflows and introduces additional points of error. Here, we show a proof-of-concept for a label-free, motion-based biomolecule detection system using electrokinetic active particles. We prepare induced-charge electrophoretic microsensors (ICEMs) for the capture of two model biomolecules, streptavidin and ovalbumin, and show that the specific capture of the biomolecules leads to direct signal transduction through ICEM speed suppression at concentrations as low as 0.1 nM. This work lays the foundation for a new paradigm of rapid, simple, and label-free biomolecule detection using active particles.
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Affiliation(s)
- Cooper
P. Thome
- Department of Chemical and
Biological Engineering, University of Colorado
Boulder, Boulder, Colorado 80303, United States
| | - Wren S. Hoertdoerfer
- Department of Chemical and
Biological Engineering, University of Colorado
Boulder, Boulder, Colorado 80303, United States
| | - Julia R. Bendorf
- Department of Chemical and
Biological Engineering, University of Colorado
Boulder, Boulder, Colorado 80303, United States
| | - Jin Gyun Lee
- Department of Chemical and
Biological Engineering, University of Colorado
Boulder, Boulder, Colorado 80303, United States
| | - C. Wyatt Shields
- Department of Chemical and
Biological Engineering, University of Colorado
Boulder, Boulder, Colorado 80303, United States
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9
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Saud KT, Solomon MJ. Microdynamics of active particles in defect-rich colloidal crystals. J Colloid Interface Sci 2023; 641:950-960. [PMID: 36989821 DOI: 10.1016/j.jcis.2023.03.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 02/04/2023] [Accepted: 03/02/2023] [Indexed: 03/11/2023]
Abstract
HYPOTHESIS Because they are self-propulsive, active colloidal particles can interact with their environment in ways that differ from passive, Brownian particles. Here, we explore how interactions in different microstructural regions may contribute to colloidal crystal annealing. EXPERIMENTS We investigate active particles propagating in a quasi-2D colloidal crystal monolayer produced by alternating current electric fields (active-to-passive particle ratio ∼ 1:720). The active particle is a platinum Janus sphere propelled by asymmetric decomposition of hydrogen peroxide. Crystals are characterized for changes in void properties. The mean-squared-displacement of Janus particles are measured to determine how active microdynamics depend on the local microstructure, which is comprised of void regions, void-adjacent regions (defined as within three particle diameters of a void), and interstitial regions. FINDINGS At active particle energy EA = 2.55 kBT, the average void size increases as much as three times and the average void anisotropy increases about 40% relative to the passive case. The average microdynamical enhancement, <δ(t)>, of Janus particles in the crystal relative to an equivalent passive Janus particle is reduced compared to that of a free, active particle (<δ(t) > is 1.88 ± 0.04 and 2.66 ± 0.08, respectively). The concentration of active particles is enriched in void and void-adjacent regions. Active particles exhibit the greatest change in dynamics relative to the passive control in void-adjacent regions (<δ(t)> = 2.58 ± 0.06). The results support the conjecture that active particle microdynamical enhancement in crystal lattices is affected by local defect structure.
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Affiliation(s)
- Keara T Saud
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, United States; Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States
| | - Michael J Solomon
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States; Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, United States.
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Marini M, Zeynali A, Collini M, Bouzin M, Sironi L, D'Alfonso L, Mantegazza F, Cassina V, Chirico G. Proteinaceous microstructure in a capillary: a study of non-linear bending dynamics. LAB ON A CHIP 2022; 22:4917-4932. [PMID: 36382419 DOI: 10.1039/d2lc00697a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The flap of bendable structures under continuous flow impacts a variety of fields, ranging from energy harvesting to active mixing in microfluidic devices. Similar physical principles determine the flapping dynamics in a variety of systems with different sizes, but a thorough investigation of the bending dynamics at the microscale is still lacking. We employ here two-photon laser polymerization to fabricate elongated proteinaceous flexible microstructures directly within a micro-capillary and we characterize their bending dynamics. The elastic properties of the microstructures with different (circular and square) cross-sections are tested by Atomic Force Microscopy and by studying the deflection-flow dependence in microfluidic experiments at intermediate Reynolds numbers (Rey ≲ 150). The retrieved Young's modulus of the fabricated matrix (100 kPa ≤ E ≤ 4 MPa) falls in the range of most typical biological tissues and solely depends on the laser fabrication intensity. The elastic constant of the microstructures falls in the range of 0.8 nN μm-1 ≤ k ≤ 50 nN μm-1, and fully agrees with the macroscopic Euler Bernoulli theory. For soft microstructures (0.8 nN μm-1 ≤ k ≤ 8 nN μm-1) we reveal undamped bending oscillations under continuous microfluidic flow, corresponding to ∼10% of the total structure deflection. This behavior is ascribed to the coupling of the viscoelasticity and non-linear elasticity of the polymer matrix with non-linear dynamics arising from the time-dependent friction coefficient of the bendable microstructures. We envision that similar instabilities may lead to the development of promising energy conversion nanoplatforms.
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Affiliation(s)
- Mario Marini
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
| | - Amirbahador Zeynali
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
| | - Maddalena Collini
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
- Bionanomedicine Center, BIONANOMIB, Via Follereau 3, 20854, Vedano al Lambro, Italy
| | - Margaux Bouzin
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
| | - Laura Sironi
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
- Bionanomedicine Center, BIONANOMIB, Via Follereau 3, 20854, Vedano al Lambro, Italy
| | - Laura D'Alfonso
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
- Bionanomedicine Center, BIONANOMIB, Via Follereau 3, 20854, Vedano al Lambro, Italy
| | - Francesco Mantegazza
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Milano-Bicocca, Via Follereau 3, 20854, Vedano al Lambro, Italy
- Bionanomedicine Center, BIONANOMIB, Via Follereau 3, 20854, Vedano al Lambro, Italy
| | - Valeria Cassina
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Milano-Bicocca, Via Follereau 3, 20854, Vedano al Lambro, Italy
- Bionanomedicine Center, BIONANOMIB, Via Follereau 3, 20854, Vedano al Lambro, Italy
| | - Giuseppe Chirico
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
- Bionanomedicine Center, BIONANOMIB, Via Follereau 3, 20854, Vedano al Lambro, Italy
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Gas generation due to photocatalysis as a method to reduce the resistance force in the process of motors motion at the air-liquid interface. J Colloid Interface Sci 2022; 627:774-782. [PMID: 35901558 DOI: 10.1016/j.jcis.2022.07.073] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 07/07/2022] [Accepted: 07/12/2022] [Indexed: 11/20/2022]
Abstract
HYPOTHESIS The problem of the development of miniature motors able to move on the air-liquid interface at low Reynolds numbers is a crucial challenge due to dominating role of viscous force. To solve this problem the chemical generation of gas can be used. Generated gas pushes liquid out from the surfer surface, so the resistance force is reduced. EXPERIMENTS Surfer composed of TiO2 nanoparticles and ferromagnetic cobalt microparticles moves at the interface of an aqueous solution of hydrogen peroxide under the action of magnetic force. After irradiation with UV or visible light, the gas cavern is formed at the surfer surface due to photo-catalytic decomposition of hydrogen peroxide. As a result, the area of surfer contact with liquid is reduced. FINDINGS The resistance force acting on the surfer is reduced due to the liquid pushing out from the surfer surface. This effect is strengthened with the increase in the intensity of gas generation. The resistance force is increased when increasing the liquid viscosity or using a surfactant. The proposed method allows control of the velocity of the motors in a rather wide range by changing the gradient of the magnetic field and parameters of light.
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12
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Das SS, Erez S, Karshalev E, Wu Y, Wang J, Yossifon G. Switching from Chemical to Electrical Micromotor Propulsion across a Gradient of Gastric Fluid via Magnetic Rolling. ACS APPLIED MATERIALS & INTERFACES 2022; 14:30290-30298. [PMID: 35748802 DOI: 10.1021/acsami.2c02605] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
To address and extend the finite lifetime of Mg-based micromotors due to the depletion of the engine (Mg-core), we examine electric fields, along with previously studied magnetic fields, to create a triple-engine hybrid micromotor for driving these micromotors. Electric fields are a facile energy source that is not limited in its operation time and can dynamically tune the micromotor mobility by simply changing the frequency and amplitude of the field. Moreover, the same electrical fields can be used for cell trapping and transport as well as drug delivery. However, the limitations of these propulsion mechanisms are the low pH (and high conductivity) environment required for Mg dissolution, while the electrical propulsion is quenched at these conditions as it requires low conductivity mediums. In order to translate the micromotor between these two extreme medium conditions, we use magnetic rolling as means of self-propulsion along with magnetic steering. Interestingly, electrical propulsion also necessitates at least the partial consumption of the Mg, resulting in a sufficient geometrical asymmetry of the micromotor. We have successfully demonstrated the rapid propulsion switching capability of the micromotor, from chemical to electrical motions, via magnetic rolling within a microfluidic device with the concentration gradient of the simulated gastric fluid. Such triple-engine micromotor propulsion holds considerable promise for in vitro studies mimicking gastric conditions and performing various bioassay tasks.
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Affiliation(s)
- Sankha Shuvra Das
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion─Israel Institute of Technology, Technion City 3200000, Israel
| | - Shahar Erez
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion─Israel Institute of Technology, Technion City 3200000, Israel
- Department of Nanoengineering, University of California San Diego, La Jolla, California 92093, United States
| | - Emil Karshalev
- Department of Nanoengineering, University of California San Diego, La Jolla, California 92093, United States
| | - Yue Wu
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion─Israel Institute of Technology, Technion City 3200000, Israel
| | - Joseph Wang
- Department of Nanoengineering, University of California San Diego, La Jolla, California 92093, United States
| | - Gilad Yossifon
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion─Israel Institute of Technology, Technion City 3200000, Israel
- School of Mechanical Engineering, Tel Aviv University, Ramat Aviv 6997801, Israel
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