Adhesion and detachment fluxes of micro-particles from a permeable wall under turbulent flow conditions

We report a numerical investigation of the deposition and re-entrainment of Brownian particles from a permeable plane wall. The tangential flow was turbulent. The suspension dynamics were obtained through direct numerical simulation of the Navier–Stokes equations coupled to the Lagrangian tracking of individual particles. Physical phenomena acting on the particles such as flow transport, adhesion, detachment and re-entrainment were considered. Brownian diffusion was accounted for in the trajectory computations by a stochastic model specifically adapted for use in the vicinity of the wall. Interactions between the particles and the wall such as adhesion forces and detachment were modeled. Validations of analytical solutions for simplified cases and comparisons with theoretical predictions are presented as well. Results are discussed focusing on the interplay between the distinct mechanisms occurring in the fouling of filtration devices. Particulate fluxes towards and away from the permeable wall are analyzed under different adhesion strengths

Elastic Tail Propulsion at Low Re

The use of microswimmers, or microscopic swimming robots, in the medical field is becoming more sought after for applications such as targeted drug delivery and microsurgery. While such microswimmers do not yet exist for use on patients, many researchers are working on this front to make them a reality. One of the main challenges in making these microswimmers a reality is creating propulsion in a low Reynolds number environment. This project aims to create and test a prototype of a swimmer which employs 3D circular movement of its tail for propulsion in a very viscous fluid, mimicking a low Reynolds environment in the macroscale. To create a successful proof of concept of 3D circular propulsion, simulations, prototyping, and experimental evaluation of the prototype were conducted during the course of this project. Finite element analysis using the commercial software COMSOL was conducted to design a swimmer tail that would generate a positive thrust force, and a velocity at an order of magnitude consistent with the analytical prediction. Guided by the simulation results, a prototype was fully realized, and testing was conducted resulting in a speed of 0.5 mm/s, which matched with the order of magnitude of the speed obtained from the simulations. The data collected from testing accompanied by simulations confirmed our proof of concept. Lastly, additional simulations were performed to find optimal parameters that can be implemented in the swimmer design for future testing. In essence, this report will provide an overview of the design, construction, and testing of a scaled-up experimental platform to examine the principle of elastic propulsion in highly viscous fluid

Development of Vortex Bioreactor Technology for Decentralised Water Treatment

The vortex bioreactor (VBR) is a simple decentralised water treatment system (DeWaTS) that sits at the interface between swirl flow, biotechnology and chemical engineering. The device utilises swirl flow and suspended activated beads to achieve downstream water processing and has been tested for applications including centrifugal-driven separation, pathogen neutralisation and metal absorption. The VBR was optimised for the treatment of faecally contaminated effluents in the developing world, and the design features related to the key challenges faced by the wastewater industry are highlighted here. The VBR has two aspects that can be modified to generate different reactor conditions: the impeller, where the swirl flow is modified through alterations of rotation speed, and impeller geometry and the suspended activated beads, which facilitate mixing and alter the reactor surface area. Data from testing for some of the different applications mentioned above are presented here, and future planned developments for the technology are discussed

Thermo-Mechanical System Identification of a Shape Memory Alloy Actuated Mechanism

Shape memory alloy (SMA) actuators paired in an antagonistic arrangement can be used to produce mechanisms that replicate human biomechanics. To investigate this proposal, the biomechanical articulation of the elbow by means of the biceps brachii muscle is compared with that of a SMA actuated arm. This is accomplished by parametric analysis of a crank-slider kinematic mechanism actuated, first, with an experimentally characterized SMA wire and then an idealized musculotendon actuator based on actuation properties of muscles published in the literature. Next, equations of motion for the system dynamics of the SMA actuated mechanism are derived and phase portrait analysis is conducted varying system parameters around different operating points. The eigenvalues of the differential equation are examined around equilibrium points and a stiffness ratio metric is proposed to characterize dynamic stability based on system parameters. Next, a heat transfer model is proposed and energy analysis is conducted on each stage of phase transformation for the SMA wire. The unknown parameters in the heat transfer model are theoretically derived and an experimental system identification is conducted. A proof of concept antagonistic SMA actuated mechanism is designed and kinematic analysis is conducted on an experimental prototype

A comprehensive survey of recent advancements in molecular communication

With much advancement in the field of nanotechnology, bioengineering and synthetic biology over the past decade, microscales and nanoscales devices are becoming a reality. Yet the problem of engineering a reliable communication system between tiny devices is still an open problem. At the same time, despite the prevalence of radio communication, there are still areas where traditional electromagnetic waves find it difficult or expensive to reach. Points of interest in industry, cities, and medical applications often lie in embedded and entrenched areas, accessible only by ventricles at scales too small for conventional radio waves and microwaves, or they are located in such a way that directional high frequency systems are ineffective. Inspired by nature, one solution to these problems is molecular communication (MC), where chemical signals are used to transfer information. Although biologists have studied MC for decades, it has only been researched for roughly 10 year from a communication engineering lens. Significant number of papers have been published to date, but owing to the need for interdisciplinary work, much of the results are preliminary. In this paper, the recent advancements in the field of MC engineering are highlighted. First, the biological, chemical, and physical processes used by an MC system are discussed. This includes different components of the MC transmitter and receiver, as well as the propagation and transport mechanisms. Then, a comprehensive survey of some of the recent works on MC through a communication engineering lens is provided. The paper ends with a technology readiness analysis of MC and future research directions

Magnetic biosensors: modelling and simulation

In the past few years, magnetoelectronics has emerged as a promising new platform technology in various biosensors for detection, identification, localisation and manipulation of a wide spectrum of biological, physical and chemical agents. The methods are based on the exposure of the magnetic field of a magnetically labelled biomolecule interacting with a complementary biomolecule bound to a magnetic field sensor. This Review presents various schemes of magnetic biosensor techniques from both simulation and modelling as well as analytical and numerical analysis points of view, and the performance variations under magnetic fields at steady and nonstationary states. This is followed by magnetic sensors modelling and simulations using advanced Multiphysics modelling software (e.g. Finite Element Method (FEM) etc.) and home-made developed tools. Furthermore, outlook and future directions of modelling and simulations of magnetic biosensors in different technologies and materials are critically discussed

Microfluidics and Nanofluidics Handbook

The Microfluidics and Nanofluidics Handbook: Two-Volume Set comprehensively captures the cross-disciplinary breadth of the fields of micro- and nanofluidics, which encompass the biological sciences, chemistry, physics and engineering applications. To fill the knowledge gap between engineering and the basic sciences, the editors pulled together key individuals, well known in their respective areas, to author chapters that help graduate students, scientists, and practicing engineers understand the overall area of microfluidics and nanofluidics. Topics covered include Finite Volume Method for Numerical Simulation Lattice Boltzmann Method and Its Applications in Microfluidics Microparticle and Nanoparticle Manipulation Methane Solubility Enhancement in Water Confined to Nanoscale Pores Volume Two: Fabrication, Implementation, and Applications focuses on topics related to experimental and numerical methods. It also covers fabrication and applications in a variety of areas, from aerospace to biological systems. Reflecting the inherent nature of microfluidics and nanofluidics, the book includes as much interdisciplinary knowledge as possible. It provides the fundamental science background for newcomers and advanced techniques and concepts for experienced researchers and professionals