scholarly journals Ultrasound-activated ciliary bands for microrobotic systems inspired by starfish

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Cornel Dillinger ◽  
Nitesh Nama ◽  
Daniel Ahmed
Keyword(s):  
Small Amplitude ◽  
Fluid Motion ◽  
Flow Characteristics ◽  
Nonlinear Acoustics ◽  
Physical Principle ◽  
Particle Manipulation ◽  
Short Hair ◽  
Bulk Fluid ◽  
Feeding Mechanism ◽  
Natural Systems

AbstractCilia 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.

scholarly journals Starfish-inspired Ultrasound Ciliary Bands for Microrobotic Systems

2021 ◽  
Author(s):  
Cornel Dillinger ◽  
Nitesh Nama ◽  
Daniel Ahmed
Keyword(s):  
Small Amplitude ◽  
Fluid Motion ◽  
Flow Characteristics ◽  
Nonlinear Acoustics ◽  
Physical Principle ◽  
Particle Manipulation ◽  
Short Hair ◽  
Bulk Fluid ◽  
Feeding Mechanism ◽  
Natural Systems

Abstract 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 cleverly utilized in microfluidics and microrobotics to achieve functionalities such as propulsion, liquid pumping and mixing, and particle manipulation. In this article, we present the first demonstration of 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 novel 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.

scholarly journals Lagrangian transport properties of pulmonary interfacial flows

2011 ◽  
Vol 705 ◽  
pp. 234-257 ◽  
Author(s):  
Bradford J. Smith ◽  
Sarah Lukens ◽  
Eiichiro Yamaguchi ◽  
Donald P. Gaver III
Keyword(s):  
Pulmonary Surfactant ◽  
Flow Characteristics ◽  
Fluid Phase ◽  
Convective Transport ◽  
Interfacial Flows ◽  
Lagrangian Analysis ◽  
Bulk Fluid ◽  
Free System ◽  
Micro Particle Image Velocimetry ◽  
Surfactant Transport

AbstractDisease states characterized by airway fluid occlusion and pulmonary surfactant insufficiency, such as respiratory distress syndrome, have a high mortality rate. Understanding the mechanics of airway reopening, particularly involving surfactant transport, may provide an avenue to increase patient survival via optimized mechanical ventilation waveforms. We model the occluded airway as a liquid-filled rigid tube with the fluid phase displaced by a finger of air that propagates with both mean and sinusoidal velocity components. Finite-time Lyapunov exponent (FTLE) fields are employed to analyse the convective transport characteristics, taking note of Lagrangian coherent structures (LCSs) and their effects on transport. The Lagrangian perspective of these techniques reveals flow characteristics that are not readily apparent by observing Eulerian measures. These analysis techniques are applied to surfactant-free velocity fields determined computationally, with the boundary element method, and measured experimentally with micro particle image velocimetry ($\ensuremath{\mu} $-PIV). We find that the LCS divides the fluid into two regimes, one advected upstream (into the thin residual film) and the other downstream ahead of the advancing bubble. At higher oscillatory frequencies particles originating immediately inside the LCS experience long residence times at the air–liquid interface, which may be conducive to surfactant transport. At high frequencies a well-mixed attractor region is identified; this volume of fluid cyclically travels along the interface and into the bulk fluid. The Lagrangian analysis is applied to velocity data measured with 0.01 mg ml−1 of the clinical pulmonary surfactant Infasurf in the bulk fluid, demonstrating flow field modifications with respect to the surfactant-free system that were not visible in the Eulerian frame.

Fluid flow analysis of cilia beating in a curved channel in the presence of magnetic field and heat transfer

2020 ◽  
Vol 98 (2) ◽  
pp. 191-197 ◽  
Author(s):  
Hina Sadaf ◽  
S. Nadeem
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Velocity Profile ◽  
Flow Analysis ◽  
Fluid Motion ◽  
Flow Characteristics ◽  
Physical Parameters ◽  
Curved Channel ◽  
Radial Magnetic Field ◽  
Fluid Flow Analysis

This paper investigates fluid motion generated by cilia and a pressure gradient in a curved channel. The flow analysis is carried out in the presence of heat transfer and radial magnetic field. The leading equations are simplified under the familiar suppositions of large wavelength and small Reynolds number approximations. An exact solution has been developed for the velocity profile. The flow characteristics of the viscous fluid are computed in the presence of cilia and metachronal wave velocity. The effects of several stimulating parameters on the flow and heat transfer are studied in detail through graphs. It is found that symmetry of the velocity profile is broken owing to bending of the channel. The radially varying magnetic field decreases the velocity field, but near the left ciliated wall it induces the opposite behavior. It is also found that velocity profile increases due to increase in buoyancy forces throughout the domain. Numerical consequences for velocity profile are also accessible in the table for diverse values of the physical parameters.

Turbulent Flow Characteristics Over Offset Wall Confined Columns in a Channel at Low Reynolds Numbers

2018 ◽  
Author(s):  
Kira Toxopeus ◽  
Kamran Siddiqui
Keyword(s):  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Turbulent Energy ◽  
Narrow Channel ◽  
Thermal Regulation ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Mean Flow ◽  
Bulk Fluid ◽  
Flow Characterization

The current study is focused on the flow through offset, wall confined vertical inserts in a channel. The columns are intended to act as the thermal storage media, which continuously exchange heat with the channel fluid to regulate it thermally. These columns could, for example, be filled with a phase change material (PCM) for passive thermal regulation, or have hot or cold fluid pumped through them for active thermal regulation. The current study has two parts: (1) the flow characterization without heat transfer, and (2) flow characterization during thermal exchange with a PCM used for regulation of bulk fluid temperature. The work presented here is focused only on the first part of the study. The experiments were conducted in a narrow channel, with water as the working fluid. Two geometries of the vertical columns (circular and square) and two offset lengths were considered. For each configuration, experiments were conducted at Reynolds numbers of 20, 50 and 90 (based of the column’s characteristic length). Particle image velocimetry was used to measure the two-dimensional velocity field in a horizontal plane at multiple regions of interest along the length of the channel to characterize the flow passing over columns. The results indicate vortex shedding at the two higher Reynolds numbers. The generation, magnitude and decay rate of turbulent energy is shown to have an offset dependency at Re = 90, but a column shape dependency at Re = 50. The mean flow has a shape dependency due to the difference in separation point over the square and circular columns.

High Resolution DCE-MRI Vascular Characterization of Murine Sarcoma and Human Renal Cell Carcinoma for Computational Modeling

2008 ◽  
Author(s):  
Gregory L. Pishko ◽  
Garrett W. Astary ◽  
Thomas H. Mareci ◽  
Malisa Sarntinoranont
Keyword(s):  
Interstitial Fluid ◽  
Tumor Tissue ◽  
Fluid Motion ◽  
Fluid Pressure ◽  
Bulk Fluid ◽  
Human Renal Cell Carcinoma ◽  
Dce Mri ◽  
Heterogeneous Tissue ◽  
Murine Sarcoma

Non-uniform extravasation from blood vessels, elevated interstitial fluid pressure (IFP), and transport by bulk fluid motion in the extracellular space have all been determined to contribute to the non-uniform tissue distribution of systemically delivered agents in solid tumors. The aforementioned factors can lead to inadequate and uneven uptake in tumor tissue which has been shown to be a major obstacle to macromolecules in clinical cancer therapy [1]. Recently developed computational tumor models have described blood flow either in a single vessel or capillary network with variations in space and time [2]. These studies do not account for heterogeneous tissue transport properties in regions of leakier vessels [3].

The radiation and scattering of surface waves by vertical barriers

1974 ◽  
Vol 63 (4) ◽  
pp. 625-634 ◽  
Author(s):  
D. Porter
Keyword(s):  
Boundary Value Problem ◽  
Surface Waves ◽  
Incident Wave ◽  
Small Amplitude ◽  
Fluid Motion ◽  
Vertical Plane ◽  
Wave Radiation ◽  
Two Dimensional ◽  
Radiation Problem ◽  
Vertical Barriers

A train of small-amplitude surface waves is incident normally on an arbitrary arrangement of thin barriers lying in a vertical plane in deep water. Each barrier is allowed to make small rolling or swaying oscillations of the same frequency as that of the incident wave. The boundary-value problem for the consequent fluid motion, assumed two-dimensional, is solved exactly using a technique which enables the amplitudes of the scattered waves far from the barriers to be readily determined. Reference is made to the associated wave radiation problem and to the calculation of forces and moments on the barriers.

The flow induced by the torsional oscillations of an elliptic cylinder

1995 ◽  
Vol 290 ◽  
pp. 279-298 ◽  
Author(s):  
N. Riley ◽  
M. F. Wybrow
Keyword(s):  
Small Amplitude ◽  
Fluid Motion ◽  
Fluid Flows ◽  
Elliptic Cylinder ◽  
Minor Axis ◽  
Oscillatory Motion ◽  
Torsional Oscillations ◽  
Steady Streaming ◽  
Axis Parallel ◽  
Streaming Flow

We consider the fluid motion induced when an elliptic cylinder performs small-amplitude torsional oscillations about an axis parallel to a generator which passes through either the centre or a point on the major or minor axis of the ellipse. In common with other fluid flows dominated by oscillatory motion, a time-independent, or steady streaming flow develops. This steady streaming exhibits several unusual and unexpected features, which are confirmed by experiment.

Investigating the Structural Properties of Corn Stover at Macro and Fiber Levels

2013 ◽  
Author(s):  
Ozan Ç. Özdemir ◽  
Taylor N. Suess ◽  
Todd M. Letcher ◽  
Stephen P. Gent
Keyword(s):  
Structural Properties ◽  
Corn Stover ◽  
Fluid Motion ◽  
Biomass Feedstock ◽  
Bulk Fluid ◽  
Three Point Bending ◽  
Transportation Equipment ◽  
Bulk Solid ◽  
Batch Systems ◽  
Pneumatic Conveyance

The purpose of this study is to analyze structural properties of biomass materials, namely corn stover. The structural properties of the biomass corn stover are examined at macro and fiber levels by performing a series of tests including three-point bending and tensile strength. Results of the stated tests are statistically analyzed. The goal of this analysis is to test the strength under loading from various directions to gather a full understanding of the structural properties of corn stalk fibers. Tests are performed using universal testing machines (UTMs). The results of these studies will be used to compile a database of the structural properties of biomass. These properties have the potential to be used in finite element computer simulations for structural analysis and bulk solid flows. The bulk fluid motion of the pulverized/chopped biomass can be simulated in storage and transportation equipment, including auguring screws and pneumatic conveyance systems, as well as devices for feeding biomass feedstocks in biorefineries. Traditional biochemical and thermochemical reactors operate as batch systems because of the difficulty of feeding the biomass feedstock in a continuous manner. Having a clearer background about the structural and rheological properties of biomass feedstock will help simulate and design the bulk-solid flows within storage bins and conveyance systems.

Natural Convection Heat Transfer From a Plate in a Semicircular Enclosure

1992 ◽  
Vol 114 (1) ◽  
pp. 121-126 ◽  
Author(s):  
G. A. Moore ◽  
K. G. T. Hollands
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Plate Thickness ◽  
Fluid Motion ◽  
Convection Heat Transfer ◽  
Bulk Fluid ◽  
Number Range ◽  
Balance Technique ◽  
Conductive Component

In the subject geometry, a long thin plate at uniform temperature is contained coaxially and symmetrically in a long semicircular trough closed at the top and having a uniform but different temperature. Heat flows across the air-filled region between the two by both natural convection and gaseous conduction. The problem of characterizing the free convective component of this heat transfer—that is, the component caused by bulk fluid motion—is treated experimentally by using a heat balance technique, with the measurements being repeated at different pressures, in order to cover a wide Rayleigh number range, from Ra ≈ 10 to Ra ≈ 108. Nusselt number versus Rayleigh number plots are presented for each of several combinations of plate-to-trough spacing and tilt angle, and the plots are correlated by equations. The problem of characterizing the conductive component is treated by numerically solving the steady diffusion equation in the air-filled region, and the results are correlated as a function of the spacing and the plate thickness.

Food Ingestion in the Estuarine Turtle Malaclemys Terrapin: Comparison With The Marine Leatherback Turtle Dermochelys Coriacea

1998 ◽  
Vol 78 (3) ◽  
pp. 953-972 ◽  
Author(s):  
V.L. Bels ◽  
J. Davenport ◽  
S. Renous
Keyword(s):  
Small Amplitude ◽  
Marine Turtle ◽  
Dermochelys Coriacea ◽  
Pressure Waves ◽  
Food Ingestion ◽  
Malaclemys Terrapin ◽  
Neck Extension ◽  
Leatherback Turtle ◽  
Feeding Mechanism ◽  
Feeding Modes

This study sheds light on the evolution of aquatic and terrestrial feeding modes in vertebrates, using two aquatic turtles as models. The estuarine aquatic diamondback turtle Malademys terrapin has a feeding mechanism that is similar to the basic feeding mechanism of terrestrial tetrapods (jaw gape cycles incorporate slow opening, fast opening, fast closing and slow closing phases). Strikes upon prey also involve neck extension and cycles of the forelimbs. Malademys terrapin modulate their feeding behaviour and jaw action in relation to the nature of the prey item. Mussels are approached by walking on the substratum, and limb cycles are of small amplitude during the strike. Crabs, whether encountered in mid-water or on the substratum, are approached by swimming, and the strikes partly produced by vigorous upstrokes of the forelimbs, that occur simultaneously with neck extension. Crabs are dangerous prey, and the turtles often strike with the gape already at maximum, minimizing the time needed to bite a limb or other part of the crab. The tongue is not involved in food capture, but has a major role in food manipulation and transport prior to swallowing. Although transport cycles are similar to ingestion cycles, ingestion and transport are easily separable in the species. Malademys terrapin exhibit great distension of the throat during the strike, but this does not appear to generate adequate suction to aid capture of hard-shelled prey; it is suggested that throat distension reduces pressures in front of the advancing snout, thus preventing pressure waves displacing or alerting prey. The pelagic marine turtle Dermodielys coriacea, which specializes in gelatinous prey, relies heavily on suction for ingestion, which overlaps considerably with transport.

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