Elastic Cilia Research Articles

Hydrodynamic synchronization of elastic cilia: How surface effects determine the characteristics of metachronal waves.

Cilia are hairlike microactuators whose cyclic motion is specialized to propel extracellular fluids at low Reynolds numbers. Clusters of these organelles can form synchronized beating patterns, called metachronal waves, which presumably arise from hydrodynamic interactions. We model hydrodynamically interacting cilia by microspheres elastically bound to circular orbits, whose inclinations with respect to a no-slip wall model the ciliary power and recovery stroke, resulting in an anisotropy of the viscous flow. We derive a coupled phase-oscillator description by reducing the microsphere dynamics to the slow timescale of synchronization and determine analytical metachronal wave solutions and their stability in a periodic chain setting. In this framework, a simple intuition for the hydrodynamic coupling between phase oscillators is established by relating the geometry of flow near the surface of a cell or tissue to the directionality of the hydrodynamic coupling functions. This intuition naturally explains the properties of the linear stability of metachronal waves. The flow near the surface stabilizes metachronal waves with long wavelengths propagating in the direction of the power stroke and, moreover, metachronal waves with short wavelengths propagating perpendicularly to the power stroke. Performing simulations of phase-oscillator chains with periodic boundary conditions, we indeed find that both wave types emerge with a variety of linearly stable wave numbers. In open chains of phase oscillators, the dynamics of metachronal waves is fundamentally different. Here the elasticity of the model cilia controls the wave direction and selects a particular wave number: At large elasticity, waves traveling in the direction of the power stroke are stable, whereas at smaller elasticity waves in the opposite direction are stable. For intermediate elasticity both wave directions coexist. In this regime, waves propagating towards both ends of the chain form, but only one wave direction prevails, depending on the elasticity and initial conditions.

Magnetically Actuated Beating Cilia for Pre-Concentration of Bacteria

Detecting low concentrations of bacteria in food samples is a challenge. The pre-concentration and separation of the target bacteria from the food matrix can be enhanced using improved fluid handling. We have demonstrated a method for pre-concentration of bacteria from a liquid sample making use of arrays of artificial cilia. The cilia are defined using thin film processes on a glass substrate and are actuated magnetically with an external magnetic field. We demonstrate particle capture with cilia, by functionalizing the surface of the cilia with streptavidin protein and capturing biotin labelled particles on its surface. The functionalized cilia are incorporated inside a microchannel and biotin labelled particles are introduced into array of the cilia. The oscillating cilia are also capable of creating a net fluid flow which can be used for fluid pumping and mixing. We study the kinematics of the elastic cilia, with their asymmetric stroke, and demonstrate that it depends on two dimensionless numbers. To demonstrate pumping effects with arrays of cilia, we incorporate them on the inner walls of microchannel loop and measure the pumping rate while varying many of the parameters of the system. We report high pumping rates and characterize the fluid handling capability of such systems in terms of two dimensionless parameters.

Simulation by using the lattice Boltzmann method of microscopic particle motion induced by artificial cilia

In this paper, we present the results obtained from the simulation of particle motion induced by the fluid flow driven by an array of beating artificial cilia inside a micro-channel. A worm-like-chain model is used to simulate the elastic cilia, and the lattice Boltzmann equation is used to compute the fluid flow. We employ a harmonic force at the extreme tip of each cilium to actuate it. Our simulation methods are first validated by applying them to the motion of a single cilium and a freely falling sphere. After validation, we simulate the fluid flow generated by an array of beating cilia and find that a maximum flow rate is achieved at an optimum sperm number. Next, we simulate the motion of a neutrally buoyant spherical particle at this optimum sperm number by tracking the particle motion with a smoothed profile method. We address the effect of the following parameters on the particle velocity: the gap between cilia and particle, the particle size, the cilia density, and the presence of an array of intermediate particles.

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.

BCM Municipal Wastewater Advanced Treatment New Technology

BCM (Biology Cilium Magnetic) technology is a kind of municipal wastewater advanced treatment technology. By using high elastic cilia filler in the oxygen unit, the volume loading of oxygen unit has been greatly increased, and more solubility pollutants could be removed in the oxygen unit. The total phosphorus and suspended substance are deeply removed by magnetic separation coagulation system. The effect of BCM technology is that all pollutants indexes could reach to the first level A standard of GB18918-2002. BCM technology is suitable for AA/O, oxidation ditch and SBR process which needs to be upgraded from the first level B to the first level A standard. The high elastic cilia filler in oxygen unit doesn’t require extra land and extra air. The magnetic separation coagulation system only needs very small land. So BCM technology is suitable for municipal wastewater treatment in China.

BAS Municipal Wastewater Advanced Treatment Process

BAS (Biochemical Adsorption Separation) process is a kind of municipal wastewater advanced treatment process which could treat municipal wastewater directly to meet the Ⅳ class of surface water standard. BAS process integrated by 4 technologies: (1) high elastic cilia filler biochemical treatment technology, (2) effluent from the facultative oxygen zone technology, (3) AZ - 01 ammonia nitrogen adsorption technology and (4) active ceramic filtration technology. The effluent quality of BAS process could reach CODCr≤30mg/L, BOD5≤6mg/L, TP≤0.3mg/L, TN≤1.5mg/L and SS≤1.5mg/L. BAS process has the advantages of easy operation, stable treatment effect, little construction and low operation cost. It is suitable use in our country special sensitive area such as Tai Lake, Dian Chi, etc. and some area which requires higher water quality.

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.

1A2-L09 次期小惑星探査ロボットのための繊毛推進機構の移動特性 : 空気浮上装置を用いた模擬微小重力実験(【宇宙工学部門】宇宙工学とロボティクス・メカトロニクス(1))

Development of a locomotion mechanism under micro-gravity is a key technology for an asteroid exploration robot in future missions. As one of the locomotion mechanisms, we have proposed a ciliary micro-hopping locomotion mechanism. The proposed mechanism is driven by an eccentric motor, and the elastic cilia enable a robot to move over an asteroid surface under micro-gravity. In this paper, we deliver fundamental locomotion characteristics of the ciliary micro-hopping mechanism based on indoor micro-gravity experiments using an air floating test bed.

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.

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.