Hierarchical assemblies of superparamagnetic colloids in time-varying magnetic fields

Spatafora-Salazar, Aldo; Lobmeyer, Dana M; Cunha, Lucas Hildebrand Pires da; Joshi, Kedar; Biswal, Sibani Lisa

doi:10.1039/d0sm01878c

Cited by 50 publications

(55 citation statements)

References 213 publications

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“…The main limitation in using external magnetic fields is the range of materials that can be controlled. These must be magnetic or contain a magnetic domain embedded in them to be susceptible to the magnetic field . The instantaneous and reversible introduction of energy is a major element of the technological appeal for electric and magnetic fields.…”

Section: Origin Of the Colloidal Response To Electric And Magnetic Fi...mentioning

confidence: 99%

“…The versatility of electric and magnetic fields is due to the ability to power nonequilibrium dissipative phenomena which can be defined as driven or active. , The definitions of these terms have evolved in the literature ,, and are critical to this review; they are summarized below: dissipative : operations that consume external energy to transition a system from an initial thermodynamic state to new states that can be in dynamic nonequilibrium or in a static kinetic trap driven : type of dissipative colloidal mechanism in which the structuring and motion of particles are directed by the global energy gradient active : type of dissipative colloidal mechanism in which the structuring and motion are governed by energy gradients local to the particles static assembly : assembly mechanism in which the final structure is maintained irrespective of the external energy source dynamic assembly : assembly mechanism forming structures that rely on transient field characteristics such as strength and frequency passive motion : migration of particles across a global gradient in field …”

Section: Introductionmentioning

confidence: 99%

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Field-Induced Assembly and Propulsion of Colloids

2022

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Electric and magnetic fields have enabled both technological applications and fundamental discoveries in the areas of bottom-up material synthesis, dynamic phase transitions, and biophysics of living matter. Electric and magnetic fields are versatile external sources of energy that power the assembly and self-propulsion of colloidal particles. In this Invited Feature Article, we classify the mechanisms by which external fields impact the structure and dynamics in colloidal dispersions and augment their nonequilibrium behavior. The paper is purposely intended to highlight the similarities between electrically and magnetically actuated phenomena, providing a brief treatment of the origin of the two fields to understand the intrinsic analogies and differences. We survey the progress made in the static and dynamic assembly of colloids and the self-propulsion of active particles. Recent reports of assembly-driven propulsion and propulsion-driven assembly have blurred the conceptual boundaries and suggest an evolution in the research of nonequilibrium colloidal materials. We highlight the emergence of colloids powered by external fields as model systems to understand living matter and provide a perspective on future challenges in the area of field-induced colloidal phenomena.

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Section: Origin Of the Colloidal Response To Electric And Magnetic Fi...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Field-Induced Assembly and Propulsion of Colloids

2022

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“…The asynchronous rotation of the spinbot was predicted to occur beyond a critical frequency of 16.7 Hz, which is defined as the step-out frequency of a magnetic microrobot. [32,40,41] Figure 2g summarizes the conditions associated with various viscosities and frequencies of magnet rotation, which allow uniform underwater rotation of the spinbots. The maximum viscosity at which the spinbot can rotate uniformly is 6.84 mPa s, which corresponds to a 50 vol% glycerol solution.…”

Section: Uniform Underwater Rotationmentioning

confidence: 99%

Agile Underwater Swimming of Magnetic Polymeric Microrobots in Viscous Solutions

Won

Kim

et al. 2022

Advanced Intelligent Systems

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Miniaturization of polymeric robots leads to difficulties in actuation inside viscous media due to the increased surface drag on the diminutive robot bodies. Herein, agile underwater swimming of polymeric microrobots is presented with the investigation of correlation between the magnetic propulsion and viscous drag on the robot. The polymeric microrobots swim with pivoting and tumbling motions during underwater rotation by in‐plane rotation of two permanent magnets underneath the plane, which results in orbital revolution‐type locomotion with a maximum swimming velocity of 56 body lengths per second (BL s−1). The rotational ability and orbital velocity of the polymeric microrobots are determined by correlated variables, i.e., liquid viscosity and frequency of magnet rotation, as elucidated by experimental results and theoretical analysis. Based on the understanding of underwater orbital maneuvers, the polymeric microrobots achieve agile swimmability at a viscosity similar to that of normal whole blood and self‐correcting maneuverability in diverse vascular‐like environments, including a stenosed tube with a coarse granular hill and a rough‐walled artificial blood vessel. Agile underwater swimming can improve versatile aquatic performances of miniaturized robots in blood vessels with arteriosclerosis or blood clots.

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“…Colloidal particles which change their physical and/or chemical state in response to external stimuli such as temperature, electrical and magnetic fields, and pH , can find numerous applications such as targeted drug delivery, biomolecular separations, smart structures, and soft actuators. − One such class of responsive materials are magnetic colloids, which alter their assembled state in response to the presence of external magnetic field. − Magnetic colloids dispersed in aqueous or nonaqueous medium, commonly known as ferrofluids, interact via magnetic forces in addition to conventional colloidal forces such as van der Waals and electrostatics. − Programming these interactions and directing the morphology of colloidal assemblies coupled in space and time is one the strategies of encoding nonequilibrium response in artificial matter. The assembly and reconfiguration of magnetic colloids is governed by the physical state of the constituting particles, which could be ferromagnetic, ferrimagnetic, or superparamagnetic. , …”

Section: Introductionmentioning

confidence: 99%

“…The assembly and reconfiguration of magnetic colloids is governed by the physical state of the constituting particles, which could be ferromagnetic, ferrimagnetic, or superparamagnetic. 21,22 Ferromagnetic materials refer to the class of magnetic materials which can retain their magnetic moment even after the external field is removed. These ferromagnetic materials have permanent dipole moment and behave as microscale magnets.…”

Section: ■ Introductionmentioning

confidence: 99%

Field-Driven Reversible Alignment and Gelation of Magneto-Responsive Soft Anisotropic Microbeads

2021

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Magnetic fields offer untethered control over the assembly, dynamics, and reconfiguration of colloidal particles. However, synthesizing "soft" colloidal particles with switchable magnetic dipole moment remains a challenge, primarily due to strong coupling of the dipoles of the adjacent nanoparticles. In this article, we present a way to overcome this fundamental challenge based on a strategy to synthesize soft microbeads with tunable residual dipole moment. The microbeads are composed of a polydimethylsiloxane (PDMS) matrix with internally embedded magnetic nanoparticles (MNPs). The distribution and orientation of the MNPs within the PDMS bead matrix is controlled by an external magnetic field during the synthesis process, thus allowing for the preparation of anisotropic PDMS microbeads with internal magnetically aligned nanoparticle chains. We study and present the differences in magnetic interactions between microbeads containing magnetically aligned MNPs and microbeads with randomly distributed MNPs. The interparticle interactions in a suspension of microbeads with embedded aligned MNP chains result in the spontaneous formation of percolated networks due to residual magnetization. We proved the tunability of the structure by applying magnetization, demagnetization, and remagnetization cycles that evoke formation, breakup, and reformation of 2D percolated networks. The mechanical response of the microbead suspension was quantified by oscillatory rheology and correlated to the propensity for network formation by the magnetic microbeads. We also experimentally correlated the 2D alignment of the microbeads to the direction of earth's magnetic field. Overall, the results prove that the soft magnetic microbeads enable a rich variety of structures and can serve as an experimental toolbox for modeling interactions in dipolar systems leading to various percolated networks, novel magneto-rheological materials, and smart gels.

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Hierarchical assemblies of superparamagnetic colloids in time-varying magnetic fields

Abstract: Time-varying magnetic fields can be used to assemble superparamagnetic colloids into hierarchically organized assemblies, ranging from 1-D chains, 2-D networks, and 2-D clusters that exhibit novel dynamics.

Cited by 50 publications

References 213 publications

Field-Induced Assembly and Propulsion of Colloids

Field-Induced Assembly and Propulsion of Colloids

Agile Underwater Swimming of Magnetic Polymeric Microrobots in Viscous Solutions

Field-Driven Reversible Alignment and Gelation of Magneto-Responsive Soft Anisotropic Microbeads

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