Magnetically Actuated Nanorod Arrays as Biomimetic Cilia (original) (raw)
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Magnetically-actuated artificial cilia for microfluidic propulsion
In this paper we quantitatively analyse the performance of magnetically-driven artificial cilia for labon-a-chip applications. The artificial cilia are fabricated using thin polymer films with embedded magnetic nano-particles and their deformation is studied under different external magnetic fields and flows. A coupled magneto-mechanical solid-fluid model that accurately captures the interaction between the magnetic field, cilia and fluid is used to simulate the cilia motion. The elastic and magnetic properties of the cilia are obtained by fitting the results of the computational model to the experimental data. The performance of the artificial cilia with a non-uniform cross-section is characterised using the numerical model for two channel configurations that are of practical importance: an open-loop and a closed-loop channel. We predict that the flow and pressure head generated by the artificial cilia can be as high as 18 microlitres per minute and 3 mm of water, respectively. We also study the effect of metachronal waves on the flow generated and show that the fluid propelled increases drastically compared to synchronously beating cilia, and is unidirectional. This increase is significant even when the phase difference between adjacent cilia is small. The obtained results provide guidelines for the optimal design of magnetically-driven artificial cilia for microfluidic propulsion.
Template-Free Preparation of Thermoresponsive Magnetic Cilia Compatible with Biological Conditions
The Journal of Physical Chemistry C
Bio-inspired materials are commonly used in the development of functional devices. The fabrication of artificial cilia mimicking the biological functions has emerged as a promising strategy for fluid manipulation in miniaturized systems. In this study, we propose a different physicochemical insight for the preparation of magnetic cilia based on the temperature-triggered reversible assembly of coated iron oxide nanoparticles in a bio-compatible template-free approach. The length of the prepared cilia could be tuned between 10 and 100 μm reaching aspect ratios up to 100 in a very dense array of flexible structures with persistence lengths around 8 μm. Magnetic actuation of the cilia revealed robust structures (over several hours of actuation) with a wide range of bending amplitudes resulting from high susceptibility of the filaments. The results demonstrate that the proposed strategy is an efficient and versatile alternative for templated fabrication methods and producing cilia with remarkable characteristics and dimensions within the template-free approaches.
Microfabricated magnetic structures for future medicine: from sensors to cell actuators
Nanomedicine, 2012
In this review, we discuss the prospective medical application of magnetic carriers microfabricated by top-down techniques. Physical methods allow the fabrication of a variety of magnetic structures with tightly controlled magnetic properties and geometry, which makes them very attractive for a cost-efficient mass-production in the fast growing field of nanomedicine. Stand-alone fabricated particles along with integrated devices combining lithographically defined magnetic structures and synthesized magnetic tags will be considered. Applications of microfabricated multifunctional magnetic structures for future medicinal purposes range from ultrasensitive in vitro diagnostic bioassays, DNA sequencing and microfluidic cell sorting to magnetomechanical actuation, cargo delivery, contrast enhancement and heating therapy.
Cells, 2021
Magnetophoresis-based microfluidic devices offer simple and reliable manipulation of micro-scale objects and provide a large panel of applications, from selective trapping to high-throughput sorting. However, the fabrication and integration of micro-scale magnets in microsystems involve complex and expensive processes. Here we report on an inexpensive and easy-to-handle fabrication process of micrometer-scale permanent magnets, based on the self-organization of NdFeB particles in a polymer matrix (polydimethylsiloxane, PDMS). A study of the inner structure by X-ray tomography revealed a chain-like organization of the particles leading to an array of hard magnetic microstructures with a mean diameter of 4 µm. The magnetic performance of the self-assembled micro-magnets was first estimated by COMSOL simulations. The micro-magnets were then integrated into a microfluidic device where they act as micro-traps. The magnetic forces exerted by the micro-magnets on superparamagnetic beads we...
Magnetic micropillars as a tool to govern substrate deformations
Lab on a Chip, 2011
Magnetic actuated microdevices can be used to achieve several complex functions in microfluidics and microfabricated devices. For example, magnetic mixers and magnetic actuators have been proposed to help handling fluids at a small scale. Here, we present a strategy to create magnetically actuated micropillar arrays. We combined microfabrication techniques and the dispersion of magnetic aggregates embedded inside polymeric matrices to design micrometre scale magnetic features. By creating a magnetic field gradient in the vicinity of the substrate, well-defined forces were applied on these magnetic aggregates which in turn induced a deflection of the micropillars. By dispersing either spherical aggregates or magnetic nanowires into the gels, we can induce synchronized motions of a group of pillars or the movement of isolated pillars under a magnetic field gradient. When combined with microfabrication processes, this versatile tool leads to local as well as global substrate actuations within a range of dimensions that are relevant for microfluidics and biological applications.
Anisotropic composite polymer for high magnetic force in microfluidic systems
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Anisotropic carbonyl iron-PolyDiMethylSiloxane (PDMS) composites were developed and implemented in microfluidic devices to serve as magnetic flux concentrators. These original materials provide technological solutions for heterogeneous integration with PDMS. Besides microfabrication advantages, they offer interesting modular magnetic properties. Applying an external magnetic field during the PDMS reticulation leads to the formation of 1D-agglomerates of magnetic particles, organized in the non-magnetic polymer matrix. This induces an increase of susceptibility as compared to composites with randomly dispersed particles. In this report, we explored the gain in reachable magnetophoretic forces in operating microfluidic devices, from the study of magnetic micro-beads motion injected in the microchannel. We show that even at relatively large distances from the magnetically-functionalized channel wall, the anisotropic composite leads to a factor two increase in the magnetophoretic force. Finally, further investigations based on finite element description suggest that the measured benefit of anisotropic composite polymers does not only rely on the global susceptibility increase but also on the local magnetic field gradients originating from the microstructure.
Nano/micro-scale magnetophoretic devices for biomedical applications
Journal of Physics D: Applied Physics, 2016
In recent years there have been tremendous advances in the versatility of magnetic shuttle technology using nano/micro-scale magnets for digital magnetophoresis. While the technology has been used for a wide variety of single-cell manipulation tasks such as selection, capture, transport, encapsulation, transfection, or lysing of magnetically labeled and unlabeled cells, it has also expanded to include parallel actuation and study of multiple bio-entities. The use of nano/micro-patterned magnetic structures that enable remote control of the applied forces has greatly facilitated integration of the technology with micro uidics, thereby fostering applications in the biomedical arena. The basic design and fabrication of various scaled magnets for remote manipulation of individual and multiple beads/cells, and their associated energies and forces that underlie the broad functionalities of this approach, are presented. One of the most useful features enabled by such advanced integrated engineering is the capacity to remotely tune the magnetic eld gradient and energy landscape, permitting such multipurpose shuttles to be implemented within lab-on-chip platforms for a wide range of applications at the intersection of cellular biology and biotechnology.
Nature-inspired microfluidic propulsion using magnetic actuation
Physical Review E, 2009
In this work we mimic the efficient propulsion mechanism of natural cilia by magnetically actuating thin films in a cyclic but non-reciprocating manner. By simultaneously solving the elasto-dynamic, magnetostatic and fluid mechanics equations, we show that the amount of fluid propelled is proportional to the area swept by the cilia. By using the intricate interplay between film magnetization and applied field we are able to generate a pronounced asymmetry and associated flow. We delineate the functional response of the system in terms of three dimensionless parameters that capture the relative contribution of elastic, inertial, viscous and magnetic forces.
Microfluidic transport in magnetic MEMS and bioMEMS
Wiley Interdisciplinary Reviews: …, 2010
Magnetic materials, such as ferrimagnetic and ferromagnetic nanoparticles and microparticles in the form of ferrofluids, can be advantageously used in microelectro-mechanical systems (MEMS) and bioMEMS applications, as they possess several unique features that provide solutions for major microfluidic challenges. These materials come with a wide range of sizes, tunable magnetic properties and offer a stark magnetic contrast with respect to biological entities. Thus, these magnetic particles are readily and precisely maneuvered in microfluidic and biological environments. The surfaces of these particles offer a relatively large area that can be functionalized with diverse biochemical agents. The useful combination of selective biochemical functionalization and 'action-at-a-distance' that a magnetic field provides makes superparamagnetic particles useful for the application in micro-total analysis systems (µ-TAS). We provide insight into the microfluidic transport of magnetic particles and discuss various MEMS and bioMEMS applications. 2010 John Wiley & Sons, Inc. WIREs Nanomed Nanobiotechnol 2010 2 382-399 T he research and development of micro-electromechanical systems (MEMS) and bioMEMS devices, which provide platforms for micro-total analytical systems (µ-TAS), 1 is driven by the need for ever-increasing miniaturization. The controlled transport of fluids and fluid-borne solids in these microfluidic environments is typically enabled through a variety of imposed influences, such as through inertial, viscous, surface tension, electrostatic, magnetic, chemical, or molecular interactions. Magnetic particles offer an enabling method that can overcome the major challenges involved with the design of lab-on-achip devices. Magnetic particle-based microfluidics is advantageous, as these particles can be influenced by 'action-at-a-distance'. This ability to manipulate them from a distance free space on microfluidic platforms to include additional components or enable multiplexed batch processing. The magnetic force that the particles experience is relatively insensitive to the biochemical environment and other physical forces, such as electrostatic, surface
Magnetic Nanoparticle Based Nanofluid Actuation With Dynamic Magnetic Fields
ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, Volume 2, 2011
Magnetic nanoparticle suspensions and their manipulation are becoming an alternative research line and have very important applications in the field of microfluidics such as microscale flow control in microfluidic circuits, actuation of fluids in microscale, and drug delivery mechanisms. In microscale, it is possible and beneficial to use magnetic fields as actuators of such nanofluids, where these fluids could move along a gradient of magnetic field so that a micropump without any moving parts could be generated with this technique. Thus, magnetically actuated nanofluids could have the potential to be used as an alternative micro pumping system. Actuation of ferrofluid plugs with a changing magnetic field has been extensively studied in the literature. However; the flow properties of ferrofluids are sparsely investigated when the ferrofluid itself is forced to continuously flow inside a channel. As an extension of previous studies, this study aims to investigate flows of magnetic nanoparticle based nanofluids by a generated magnetic field and to compare the efficiency of the resulting system. Lauric Acid coated Super Paramagnetic Iron Oxide (SPIO-LA) was used as the ferrofluid sample in the experiments to realise actuation. Significant flow rates up to 61.8μL/s at nominal maximum magnetic field strengths of 300mT were achieved in the experiments. Results suggest that nanofluids with magnetic nanoparticles merit more research efforts in micro pumping. Thus, magnetic actuation could be a significant alternative for more common techniques such as electromechanical, electrokinetic, and piezoelectric actuation.