A Passive Micromixer for Bioanalytical Applications

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Three passive micromixers with different geometries, i.e. zigzag, spiral, and split and merge (SaM) with labyrinthine channels, are compared with respect to their mixing efficiency by means of a computational study. The specifications are imposed from flexible printed circuit (FPC) technology which is used for their fabrication and from the applications to be implemented, i.e. the mixing of biochemical reagents. The computations include the numerical solution of continuity, Navier-Stokes, and mass conservation equations in 3d by ANSYS Fluent. The highest mixing efficiency is calculated for the SaM micromixer with the labyrinthine channel. Compared to a linear micromixer, the spiral micromixer improves the mixing efficiency by 8%, the zigzag by 11%, and the SaM by 92%; the diffusion coefficient of the biomolecule is 10-10 m2/s, the Reynolds number is 0.5, and the volume of each micromixer is 2.54 μl. The best of the three designs is realized by FPC technology and is experimentally evaluated by fluorescence microscopy

Physics and Applications of a PDMS Based Centrifugal Microfluidic System

The objective of this research work is to develop a centrifugal microfluidic system for general purposes based on microfabrication technologies including SU-8 photolithography, polydimethylsiloxane (PDMS) casting. The main contribution of this research is to integrate a flyball governor system into the polymer based centrifugal microfluidic platform. A series of function units are developed based on this unique mechanism. In the first part, three pinch valve systems were designed and tested. The first one is based on the magnetic force and the second one is on the basis of spring force and the last one is a membrane valve. All valving system demonstrate good control of the fluid movement. The latter two valves are capable of sequential control. It proves that the flyball governor system is very compatible with centrifugal fluidic technologies. The major advantage of this new actuation technology is that its burst frequency can be conveniently manipulated by adjusting the parameters of the mechanical system without changes in the fluidic pattern. Next, two types of inward pumping systems were designed and tested. The result shows that both the inward pumps were capable of the pumping over a radial distance of 21mm in a short time. It thus improves the usage of space on the disc and paves the way to interconnect several functional units. Then as a proof of concept, a sequential valving system capable of metering and centrifugal sediment was developed for plasma extraction from whole blood. The resulting residual cell concentration was less than 0.5%. In the last part, a micromixer was developed based on the similar principle. The results show that the flyball governor system can effectively agitate the chaotic mixing of the sample liquids by periodically deflecting the PDMS membrane of the mixing chamber. The mixing effect can thus be enhanced

Numerical and Experimental Study of Cross-Sectional Effects on the Mixing Performance of the Spiral Microfluidics.

Mixing at the microscale is of great importance for various applications ranging from biological and chemical synthesis to drug delivery. Among the numerous types of micromixers that have been developed, planar passive spiral micromixers have gained considerable interest due to their ease of fabrication and integration into complex miniaturized systems. However, less attention has been paid to non-planar spiral micromixers with various cross-sections and the effects of these cross-sections on the total performance of the micromixer. Here, mixing performance in a spiral micromixer with different channel cross-sections is evaluated experimentally and numerically in the Re range of 0.001 to 50. The accuracy of the 3D-finite element model was first verified at different flow rates by tracking the mixing index across the loops, which were directly proportional to the spiral radius and were hence also proportional to the Dean flow. It is shown that higher flow rates induce stronger vortices compared to lower flow rates; thus, fewer loops are required for efficient mixing. The numerical study revealed that a large-angle outward trapezoidal cross-section provides the highest mixing performance, reaching efficiencies of up to 95%. Moreover, the velocity/vorticity along the channel length was analyzed and discussed to evaluate channel mixing performance. A relatively low pressure drop (<130 kPa) makes these passive spiral micromixers ideal candidates for various lab-on-chip applications

Information management and psm evaluation system

Information Management and PSM Evaluation System is a system developed to replace the existing system at the Faculty of Computing. The existing system at the Faculty of Computing is a manual system in which all the evaluation process still utilises paper forms. PSM is divided into two phases; PSM1 and PSM2 and each phase has a different form for evaluation. This process is seen to be less systematic and imposes much time on the evaluator, coordinator and supervisor who are also lecturers. Information Management and PSM Evaluation System is designed to automate information management and evaluation of PSM to keep the information in the database. The scope of these systems focuses on admin, supervisor, evaluator and coordinator bound to PSM1 and PSM2. Some of the functions that can be operated on the system are evaluation, updating PSM students’ information and generating reports. The chosen methodology is an Evolutionary Prototype which needs are taken care of the system during modifications. Requirements established during the interview is employed to form a common structure with the essential basic functions of the system. Therefore, Information Management and PSM Evaluation System was developed to automate the manual system to increase efficiency. The system was developed using ASP.net technology and Microsoft Visual Studio 2010 and has been successfully completed within the specified time

Mixing Enhancement in Serpentine Micromixers with a Non-Rectangular Cross-Section

In this numerical study, a new type of serpentine micromixer involving mixing units with a non-rectangular cross-section is investigated. Similar to other serpentine/spiral shaped micromixers, the design exploits the formation of transversal vortices (Dean flows) in pressure-driven systems, associated with the centrifugal forces experienced by the fluid as it is confined to move along curved geometries. In contrast with other previous designs, though, the use of non-rectangular cross-sections that change orientation between mixing units is exploited to control the center of rotation of the transversal flows formed. The associated extensional flows that thus develop between the mixing segments complement the existent rotational flows, leading to a more complex fluid motion. The fluid flow characteristics and associated mixing are determined numerically from computational solutions to Navier–Stokes equations and the concentration-diffusion equation. It is found that the performance of the investigated mixers exceeds that of simple serpentine channels with a more consistent behavior at low and high Reynolds numbers. An analysis of the mixing quality using an entropic mixing index indicates that maximum mixing can be achieved at Reynolds numbers as small as 20 in less than four serpentine mixing units

Integration of functional materials into microfluidic devices for fluidic control and sensing

165 p.El agua es una fuente clave para el buen estado de las personas y, en la naturaleza, es una fuente nutritiva esencial responsable del crecimiento de la vegetación. Por ello, la monitorización de la calidad del agua es de gran importancia para la sociedad. En esta tesis se pretende contribuir a un futuro donde sensores altamente autónomos y eficaces son capaces de medir y compartir la información de la calidad de nuestro medio ambiente, en particular, de las diferentes matrices de agua. En este sentido, se han desarrollado diferentes módulos para contribuir con bajo coste y tecnología de rápida fabricación a la monitorización continuada de la calidad del agua. Para conseguir reducir los costes asociados a la producción de componentes convencionales, se han implementado materiales inteligentes dentro de dispositivos microfluídicos para conseguir el control fluídico y sensórico

High-Efficiency Small Sample Microparticle Fractionation on a Femtosecond Laser-Machined Microfluidic Disc

The fabrication and testing of microfluidic spinning compact discs with embedded trapezoidal microchambers for the purpose of inertial microparticle focusing is reported in this article. Microparticle focusing channels require small features that cannot be easily fabricated in acrylic sheets and are complicated to realize in glass by traditional lithography techniques; therefore, the fabrication of microfluidic discs with femtosecond laser ablation is reported for the first time in this paper. It could be demonstrated that high-efficiency inertial focusing of 5 and 10 µm particles is achieved in a channel with trapezoidal microchambers regardless of the direction of disc rotation, which correlates to the dominance of inertial forces over Coriolis forces. To achieve the highest throughput possible, the suspension concentration was increased from 0.001% (w/v) to 0.005% (w/v). The focusing efficiency was 98.7% for the 10 µm particles and 93.75% for the 5 µm particles

Passive Micromixers

Micro-total analysis systems and lab-on-a-chip platforms are widely used for sample preparation and analysis, drug delivery, and biological and chemical syntheses. A micromixer is an important component in these applications. Rapid and efficient mixing is a challenging task in the design and development of micromixers. The flow in micromixers is laminar, and, thus, the mixing is primarily dominated by diffusion. Recently, diverse techniques have been developed to promote mixing by enlarging the interfacial area between the fluids or by increasing the residential time of fluids in the micromixer. Based on their mixing mechanism, micromixers are classified into two types: active and passive. Passive micromixers are easy to fabricate and generally use geometry modification to cause chaotic advection or lamination to promote the mixing of the fluid samples, unlike active micromixers, which use moving parts or some external agitation/energy for the mixing. Many researchers have studied various geometries to design efficient passive micromixers. Recently, numerical optimization techniques based on computational fluid dynamic analysis have been proven to be efficient tools in the design of micromixers. The current Special Issue covers new mechanisms, design, numerical and/or experimental mixing analysis, and design optimization of various passive micromixers

Analysis, Design and Fabrication of Micromixers

This book includes an editorial and 12 research papers on micromixers collected from the Special Issue published in Micromachines. The topics of the papers are focused on the design of micromixers, their fabrication, and their analysis. Some of them proposed novel micromixer designs. Most of them deal with passive micromixers, but two papers report studies on electrokinetic micromixers. Fully three-dimensional (3D) micromixers were investigated in some cases. One of the papers applied optimization techniques to the design of a 3D micromixer. A review paper is also included and reports a review of recently developed passive micromixers and a comparative analysis of 10 typical micromixers

Technologies for a user-friendly microfluidic system for portable applications.

Master of Medical Science in Medical Microbiology. University of KwaZulu-Natal, Medical School 2015.In the same way that the HIV virus subdues the human immune system, the HIV/AIDS epidemic has severely overloaded the health service infrastructure in resource limited countries and threatens to systematically suppress societies’ capacity to cope with killer diseases. The epidemic has also directly impacted the health workforce, causing absenteeism, attrition (due to illness and death), and increased demand for provider time and skills. Advanced and miniaturized microfluidic systems can perform complex biotechnological functions such as growing bacteria, sequencing DNA and identifying disease causing pathogens. As a technology, microfluidics offers so many advantages but it also suffers from a variety of technological drawbacks that limit its wide spread practical application in hospitals and patient setting. Microfluidic systems require a lot of time (6 hours to an entire work-day) to set up and the set-up process requires the meticulous attention of highly trained personnel. We proposed the development of an automated, time conservative and user-friendly fluid-transport system (off-chip to on-chip) for Microfluidic Large Scale Integration platform based microfluidic devices. Using multilayer soft-lithography, micro-electric actuators and a LabVIEW graphical user-interface, a user-friendly automated microfluidic fluid transport system was developed. In comparison to the conventional manual loading system, the developed system can save at least 60% of the total chip preparation time required during the off-chip to on-chip fluid loading process. This system can be extended and made compatible with other devices that require complex off-chip to on-chip loading processes in microfluidic large scale integration platform based systems