Synthetic Cilia Research Articles

Electroosmotic MHD ternary hybrid Jeffery nanofluid flow through a ciliated vertical channel with gyrotactic microorganisms: Entropy generation optimization

In this study, the computational analysis of entropy generation optimization for synthetic cilia regulated ternary hybrid Jeffery nanofluid (Ag–Au–TiO2/PVA) flow through a peristaltic vertical channel with swimming motile Gyrotactic microorganisms is investigated. Understanding the intricate interaction of multiple physical phenomena in biomedical applications is essential for optimizing entropy generation and advancing microfluidic systems. The characteristics of nanofluid are explored for the electroosmotic MHD fluid flow in the presence of thermophoresis and Brownian motion, viscous dissipation, Ohmic heating and chemical reaction. Using the appropriate transformations, a set of ordinary differential equations are created from the governing partial differential equations. The resulting ODEs are numerically solved using the shooting technique using BVP5C in MATLAB after applying the long-wavelength and low Reynolds number approximation. The velocity, temperature, concentration, electroosmosis, and microorganism density profiles are analyzed graphically for different emerging parameters. Graphical investigation of engineering interest quantities like heat transfer rate, mass transfer rate, skin friction coefficient, and entropy generation optimization are also presented. It is observed that the rate of mass transfer increases for increasing thermophoretic parameter, while reverse effect is noted for Brownian motion parameter, Schmidt number, and chemical reaction number. The outcomes of present study can be pertinent in studying Cilia properties of respiratory tract, reproductive system, and brain ventricles.

Entropy generation optimization of cilia regulated MHD ternary hybrid Jeffery nanofluid with Arrhenius activation energy and induced magnetic field

This study deals with the entropy generation analysis of synthetic cilia using a ternary hybrid nanofluid (Al–Cu–Fe2O3/Blood) flow through an inclined channel. The objective of the current study is to investigate the effects of entropy generation optimization, heat, and mass transfer on ternary hybrid nanofluid passing through an inclined channel in the proximity of the induced magnetic field. The novelty of the current study is present in studying the combined effect of viscous dissipation, thermophoresis, Brownian motion, exponential heat sink/source, porous medium, endothermic–exothermic chemical reactions, and activation energy in the proximity of induced magnetic field is examined. The governing partial differential equations (PDEs) are transformed into the ordinary differential equations (ODEs) using appropriate transformations. Applying the low Reynolds number and the long-wavelength approximation, resultant ODEs are numerically solved using shooting technique via BVP5C in MATLAB. The velocity, temperature, concentration, and induced magnetism profiles are visually discussed and graphically analyzed for various fluid flow parameters. Graphical analysis of physical interest quantities like mass transfer rate, heat transfer rate, entropy generation optimization, and skin friction coefficient are also graphically discussed. The entropy generation improves for enhancing values of Reynolds number, solutal Grashof number, heat sink/source parameter, Brinkman number, magnetic Prandtl number, and endothermic-exothermic reaction parameter while the reverse effect is noticed for chemical reaction and induced magnetic field parameter. The findings of this study can be applied to enhance heat transfer efficiency in biomedical devices, optimizing cooling systems, designing efficient energy conversion processes, and spanning from renewable energy technologies to aerospace propulsion systems.

Ultrasound-activated ciliary bands for microrobotic systems inspired by starfish

Cilia are short, hair-like appendages ubiquitous in various biological systems, which have evolved to manipulate and gather food in liquids at regimes where viscosity dominates inertia. Inspired by these natural systems, synthetic cilia have been developed and utilized in microfluidics and microrobotics to achieve functionalities such as propulsion, liquid pumping and mixing, and particle manipulation. Here, we demonstrate ultrasound-activated synthetic ciliary bands that mimic the natural arrangements of ciliary bands on the surface of starfish larva. Our system leverages nonlinear acoustics at microscales to drive bulk fluid motion via acoustically actuated small-amplitude oscillations of synthetic cilia. By arranging the planar ciliary bands angled towards (+) or away (−) from each other, we achieve bulk fluid motion akin to a flow source or sink. We further combine these flow characteristics with a physical principle to circumvent the scallop theorem and realize acoustic-based propulsion at microscales. Finally, inspired by the feeding mechanism of a starfish larva, we demonstrate an analogous microparticle trap by arranging + and − ciliary bands adjacent to each other.

Entropy generation in thermally radiated hybrid nanofluid through an electroosmotic pump with ohmic heating: Case of synthetic cilia regulated stream.

Synthetic cilia-regulated transports through micro and nanofluidic devices guarantee an efficient delivery of drugs and other biological substances. Entropy analysis of cilia stimulated transport of thermally radiated hybrid nanofluid through an electroosmotic pump is conducted in this study. Joint effects of applied Lorentz force and Ohmic heating on the intended stream are also studied. Metachronal arrangements of cilia field coating channel inner side, are liable to generate current in the fluid. After using the lubrication and the Debye-Huckel estimations, numerical solutions of the envisioned problem are obtained. For pressure rise per metachronal wavelength, the pressure gradient is numerically integrated. The analysis reveals that high electric potential results in reducing the heat transfer effects in the flow system. The enhancement of flow is noticed near the channel surface for higher electroosmotic parameters. The irreversibility in the channel decreases when the Helmholtz-Smoluchowski velocity is applied in the opposite direction of the flow and thus produces the fluid friction irreversibility.

Thermal analysis of double diffusive electrokinetic thermally radiated TiO2-Ag/blood stream triggered by synthetic cilia under buoyancy forces and activation energy

Second law analysis of double diffusive cilia endorsed transport of thermally radiated hybrid nanofluid through an electroosmotic pump is deliberated in this study. Joint effects of applied Lorentz force, activation energy and Joule heating on the proposed stream are also examined. Channel inner surface is shielded with artificial cilia carpet that ensures flow induction and micro-mixing activity in the fluid. After applying the lubrication and the Debye-Huckel estimations, numerical solutions of the envisioned problem are calculated. The analysis reveals that the elevated electric potential and prolonged cilia assist directional flow spreads over large distances. The augmentation in fluid stream is seen near the channel surface for higher electroosmotic parameter. Presence of activation energy input and thin electric double layer supports mass dispersion and control heat indulges. The present model provides an immediate understanding about the promising role of fabricated cilia in electroosmotic pumps for the future biomimetic micro and nanofluidic devices.

Entropy Analysis of an MHD Synthetic Cilia Assisted Transport in a Microchannel Enclosure with Velocity and Thermal Slippage Effects

The magnitude of shear stress at the ciliated wall is considered as the measure of efficiency of cilia beatings as it describes the momentum transfer between the medium and the cilia. Under high shear rate, some non-Newtonian fluids behave as visco-inelastic fluids. We consider here a ciliated channel coated with Prandtl fluid, a visco-inelastic fluid, with Hartmann layer under momentum and thermal slip effects. The flow in the channel is produced due to beatings of cilia that obey an elliptic path of motion in the flow direction. An entropy analysis of the flow is also conducted in wave frame. After introducing lubrication approximations in the governing equation, the perturbation solutions are calculated. The data for pressure rise per metachronal wavelength and frictional force at the ciliated wall are obtained by numerical integration. The analysis reveals that the higher values of cilia length and velocity slip parameters support fluid flow near the channel wall surface. Fluid temperature is an increasing function of thermal slip but a decreasing function of cilia length and slip parameters. Entropy in the channel can be minimized with an increase in cilia length and slip effect at the boundary. The magnitude of the heat transfer coefficient decreases by taking the substantial slippage and tiny cilia in length at the microchannel wall.

Microfluidic pumping using artificial magnetic cilia

One of the vital functions of naturally occurring cilia is fluid transport. Biological cilia use spatially asymmetric strokes to generate a net fluid flow that can be utilized for feeding, swimming, and other functions. Biomimetic synthetic cilia with similar asymmetric beating can be useful for fluid manipulations in lab-on-chip devices. In this paper, we demonstrate the microfluidic pumping by magnetically actuated synthetic cilia arranged in multi-row arrays. We use a microchannel loop to visualize flow created by the ciliary array and to examine pumping for a range of cilia and microchannel parameters. We show that magnetic cilia can achieve flow rates of up to 11 μl/min with the pressure drop of ~1 Pa. Such magnetic ciliary array can be useful in microfluidic applications requiring rapid and controlled fluid transport.

From Extensile Microtubules Bundles to Synthetic Cilia and Self-Mixing Active Gels

In presence of a macromolecular crowding agent filamentous microtubules spontaneously assemble into elongated bundles. Kinesin clusters can simultaneously bind to multiple filaments within such a bundle and thus power relative sliding of the constituent filaments and the overall bundle extension. Starting with such extensile bundles it is possible to hierarchically assemble diverse biologically inspired materials including spontaneously beating synthetic cilia, self-mixing and self-flowing active gels, motile emulsion droplets as well as deformable vesicles. However, little is known about the mechanical properties of isolated active extensile bundles that are the essential structural motif of these diverse materials. We describe an experimental technique that allows us to systematically assemble filamentous bundles with predetermined number of filaments and quantify its ability to generate extensile force.

Enhancing nanoparticle deposition using actuated synthetic cilia

We use computational modeling to probe the utility of actuated synthetic cilia lining walls of a microfluidic channel for enhancing the deposition of nanoparticles dispersed in a viscous fluid filling the channel. We demonstrate that elastic cilia actuated by a sinusoidal force applied to their free ends generate circulatory secondary flows facilitating nanoparticle transport. We identify optimal operational conditions in which the effect of cilia beating on particle deposition is maximized. Our simulations also reveal that cilia transition to a three-dimensional beating pattern when the actuation force exceeds a critical value. This transition is associated with buckling instability experienced by elastic cilia. Our findings guide the optimal design of ciliated microfluidic systems for uses such as deposition of particulates onto sensory surfaces and microfluidic mixing.

NPHP and MKS proteins and the ciliary transition zone

The cilium has emerged as an important signaling and sensory organelle needed for mammalian development and adult tissue homeostasis. It mediates these effects by locating specific receptors, channels, and other signaling factors needed for pathway regulation along the cilium membrane and axoneme. To establish the cilia signaling complement of proteins distinct from that of the cytosol or cell membrane there is a domain called the transition zone (TZ) located at the base that is believed to function as a diffusion barrier, restricting protein entry or exit from the cilium. The structure of the TZ has been well defined through EM analysis, but the proteins required to generate the TZ are only now being identified. Using C. elegans models, we have shown that many of the proteins involved in human ciliopathies such as Meckel Gruber syndrome (MKS) and Nephronophthisis (NPHP) grossly localize to the TZ. We are currently defining where these proteins localize on structures within the TZ using higher resolution EM approaches. Further, the NPHP and MKS proteins form two genetically interacting complexes in C. elegans that when disrupted result in the loss of structures in the TZ, inappropriate ciliary localization of nonciliary proteins, and severe cilia assembly/positioning defects. Based on the synthetic cilia phenotype observed in all mks;nphp double mutants that we generated thus far, we conducted an EMS enhancer screen using nphp-4 single mutants. The goal of the screen was to generate secondary mutations that would genetically interact with the initial nphp-4 mutation. Our prediction is that this would yield novel mutations in proteins that function with the MKS or NPHP complexes and would thus provide ideal candidates for novel loci involved in human ciliopathies patients. Using whole genome sequence analysis, we have begun identifying the affected genes. As predicted, three of the alleles were in known MKS genes. Several other mutations in cilia genes have been identified but have not previously been associated with either NPHP or MKS. The role of these genes and the interaction with the NPHP and MKS complexes are being further explored in both C. elegans and mouse models. Understanding how the TZ forms and how mutations in TZ proteins disrupt the diffusion barrier will provide important insights into the ciliopathies and how this organelle serves its diverse signaling and sensory functions.

Propulsion and Trapping of Microparticles by Active Cilia Arrays

We model the transport of a microscopic particle via a regular array of beating elastic cilia, whose tips experience an adhesive interaction with the particle's surface. At optimal adhesion strength, the average particle velocity is maximized. Using simulations spanning a range of cilia stiffness and cilia-particle adhesion strength, we explore the parameter space over which the particle can be "released", "propelled", or "trapped" by the cilia. We use a lower-order model to predict parameters for which the cilia are able to "propel" the particle. This is the first study that shows how both stiffness and adhesion strength are crucial for manipulation of particles by active cilia arrays. These results can facilitate the design of synthetic cilia that integrate adhesive and hydrodynamic interactions to selectively repel or trap particulates. Surfaces that are effective at repelling particulates are valuable for antifouling applications, while surfaces that can trap and, thus, remove particulates from the solution are useful for efficient filtration systems.

Beating synthetic cilia enhance heat transport in microfluidic channels

Using computational modeling, we probed the utility of actuated synthetic cilia for enhancing heat transport in microfluidic channels. Cilia are elastic filaments that are attached to the bottom channel wall with a constant tilt and actuated by a periodical vertical force applied to their free ends. We show that periodical oscillations of elastic cilia mix the heated fluid and create secondary flows in the microchannel that facilitate heat transport between channel walls. The magnitude of the secondary flows and the cilium deformation pattern are controlled by the frequency and amplitude of the periodic driving force. Thus, by varying the force parameters one can effectively regulate the local heat transport in ciliated microchannels.

Harnessing synthetic cilia to regulate motion of microparticles

Functional synthetic cilia lining solid surfaces could potentially yield a unique approach for regulating transport processes at interfaces. We use computer simulations to probe how non-motile and actuated cilia can be harnessed to control the motion of microscopic particles suspended in a Newtonian fluid. We show that biomimetic cilia can be arranged to create hydrodynamic currents that can either direct particles towards the ciliated surface or expel them away, thereby modifying the effective interactions between solid surfaces and particulates. In addition to revealing new approaches for regulating the microscale particle transport, our findings point to a new strategy for creating functional materials that employ active and responsive synthetic cilia.

Designing ciliated surfaces that regulate deposition of solid particles

Using computational modeling, we examine a pressure-driven fluid flow in a microchannel lined with regularly-spaced non-motile elastic cilia. Our simulations reveal that solid, neutrally-buoyant particles moving with the fluid can be effectively directed towards channel walls by synthetic cilia, thereby inducing their rapid deposition. This particle lateral migration takes place due to circulatory secondary flows emerging within a layer of compliant cilia. Our results suggest that synthetic ciliated surfaces could be harnessed for hydrodynamic separation, trapping, and filtration of microscopic biological and synthetic particles in microfluidic devices.

Designing Oscillating Cilia That Capture or Release Microscopic Particles

We use computational modeling to capture the three-dimensional interactions between oscillating, synthetic cilia and a microscopic particle in a fluid-filled microchannel. The synthetic cilia are elastic filaments that are tethered to a substrate and are actuated by a sinusoidal force, which is applied to their free ends. The cilia are arranged in a square pattern, and a neutrally buoyant particle is initially located between these filaments. Our computational studies reveal that, depending on frequency of the beating cilia, the particle can be either driven downward toward the substrate or driven upward and expelled into the fluid above the cilial layer. This behavior mimics the performance of biological cilia used by certain marine animals to extract suspended food particles. The findings uncover a new route for controlling the deposition of microscopic particles in microfluidic devices.

Designing Synthetic, Pumping Cilia That Switch the Flow Direction in Microchannels

Using computational modeling, we simulate the 3D movement of actuated cilia in a fluid-filled microchannel. The cilia are modeled as deformable, elastic filaments, and the simulations capture the complex fluid-structure interactions among these filaments, the channel walls, and the surrounding solution. The cilia are tilted with respect to the surface and are actuated by a sinusoidal force that is applied at the free ends. We find that these cilia give rise to a unidirectional flow in the system and by simply altering the frequency of the applied force we can controllably switch the direction of the net flow. The findings indicate that beating, synthetic cilia could be harnessed to regulate the fluid streams in microfluidic devices.