Research Interests: Mechanical Engineering, Condensed Matter Physics, Microfluidics, Light Scattering, Magnetic field, and 10 moreMagnetic particles, Magnetic Susceptibility, Magnetic separation, Laminar Flow, Chip, Continuous Flow, Superparamagnetism, Magnetism and Magnetic Materials, Flow Rate, and Laser Light Scattering
The processing of particles, cells, and droplets for reactions, analyses, labeling, and coating is an important aspect of many microfluidic workflows. However, performing multi-step processes is typically a laborious and time-consuming... more
The processing of particles, cells, and droplets for reactions, analyses, labeling, and coating is an important aspect of many microfluidic workflows. However, performing multi-step processes is typically a laborious and time-consuming endeavor. By exploiting the laminar nature of flow within microchannels, such procedures can benefit in terms of both speed and simplicity. This can be achieved either by manipulating the flow streams around the objects of interest, particularly for the localized perfusion of cells, or by manipulating the objects themselves within the streams via a range of forces. Here, we review the variety of methods that have been employed for performing such “multilaminar flow” procedures on particles, cells, and droplets.
Research Interests:
We report the rapid on-chip generation and subsequent manipulation of magnetic droplets in continuous flow. Magnetic droplets were formed using aqueous-based ferrofluid as the dispersed phase and fluorocarbon oil as the continuous phase.... more
We report the rapid on-chip generation and subsequent manipulation of magnetic droplets in continuous flow. Magnetic droplets were formed using aqueous-based ferrofluid as the dispersed phase and fluorocarbon oil as the continuous phase. Droplet manipulation was demonstrated with simple permanent magnets using two microfluidic platforms: (i) flow focusing droplet generation followed by their splitting into daughter droplets containing different amounts of magnetic nanoparticles, and (ii) droplet generation at a T-junction and their downstream deflection across a chamber for sorting based on the applied magnetic field and magnetite loading of the droplet. Both systems show great potential for performing a wide range of high throughput continuous flow processes including sample dilution, cell sorting and screening, and microparticle fabrication.
We explore the potential of a microfluidic continuous flow particle separation system based on the repulsion of diamagnetic materials from a high magnetic field. Diamagnetic polystyrene particles in paramagnetic manganese (II) chloride... more
We explore the potential of a microfluidic continuous flow particle separation system based on the repulsion of diamagnetic materials from a high magnetic field. Diamagnetic polystyrene particles in paramagnetic manganese (II) chloride solution were pumped into a microfluidic chamber and their deflection behaviour in a high magnetic field applied by a superconducting magnet was investigated. Two particle sizes (5 and 10 μm) were examined in two concentrations of MnCl2 (6 and 10%). The larger particles were repelled to a greater extent than the smaller ones, and the effect was greatly enhanced when the particles were suspended in a higher concentration of MnCl2. These findings indicate that the system could be viable for the separation of materials of differing size and/or diamagnetic susceptibility, and as such could be suitable for the separation and sorting of small biological species for subsequent studies.
Research Interests:
We demonstrate the application of magnetic forces for the simultaneous trapping of two types of particles, magnetic and diamagnetic, via a single set of magnets. Furthermore, we show how this simple setup can be employed for performing... more
We demonstrate the application of magnetic forces for the simultaneous trapping of two types of particles, magnetic and diamagnetic, via a single set of magnets. Furthermore, we show how this simple setup can be employed for performing assays with a negative control, or for achieving multiple simultaneous analyses.
We are exploring the use of magnetic attraction and diamagnetic repulsion forces for the handling of microparticles and cells in microchannels. Here, we report on the application of both of these types of forces to allow simultaneous... more
We are exploring the use of magnetic attraction and diamagnetic repulsion forces for the handling of microparticles and cells in microchannels. Here, we report on the application of both of these types of forces to allow simultaneous trapping of magnetic and diamagnetic particles via a single set of magnets, and demonstrate the ability to perform assays on one type of particle while the other acts as a control. Additionally, we show how the setup can be adjusted to enable the continuous flow focusing of diamagnetic particles in a paramagnetic medium.
Microfluidics concerns the manipulation of small volumes of fluids (typically nanoliters or less) within networks of channels that have dimensions of tens to hundreds of micrometers. Such devices benefit from having small footprints, low... more
Microfluidics concerns the manipulation of small volumes of fluids (typically nanoliters or less) within networks of channels that have dimensions of tens to hundreds of micrometers. Such devices benefit from having small footprints, low volume requirements of samples and reagents, short analysis times, and a large degree of control over processes being performed, allowing miniaturization of single or multiple laboratory-based procedures and giving rise to ‘lab-on-a-chip’ technology. Microfluidic platforms have become powerful tools in a broad range of fields, from chemistry and engineering to the life sciences, and are revolutionizing the way research can be performed and the quality of information that can be gained.
Free-flow magnetophoresis is becoming a popular technique for the separation and manipulation of magnetic particles and materials in microsystems. A wide variety of magnetic particles are commercially available that differ greatly in size... more
Free-flow magnetophoresis is becoming a popular technique for the separation and manipulation of magnetic particles and materials in microsystems. A wide variety of magnetic particles are commercially available that differ greatly in size and in magnetic properties. To investigate the suitability of different particle types for magnetophoretic operations in microfluidic devices, we compared a range of particles from three manufacturers by pumping them through a microfluidic separation chamber and deflecting them from the direction of laminar flow by applying an external magnetic field. The on-chip deflection of particles was compared to data provided by the manufacturers and magnetisation data obtained from vibrating sample magnetometer (VSM) measurements. Additionally, the extent of deflection was examined over a range of temperatures. Deflection distances were found to increase significantly with increasing temperature. Further to this, a separation of 2.8 and 1.0 μm magnetic particles was performed at different temperatures. Separation resolution was found to improve at higher temperatures. Hence, temperature manipulation provides a simple and effective means for improving a magnetic separation or for controlling the angle at which a particle is deflected from its hydrodynamic flow path.
Research Interests:
We demonstrate a rapid method of coating a layer of polymer onto magnetically modified yeast cells, so-called “cyborg cells”, in continuous flow within a microfluidic chamber. Laminar flow streams of polyelectrolyte and washing buffers... more
We demonstrate a rapid method of coating a layer of polymer onto magnetically modified yeast cells, so-called “cyborg cells”, in continuous flow within a microfluidic chamber. Laminar flow streams of polyelectrolyte and washing buffers were generated across the chamber, and the magnetic cells were deflected sequentially through the co-flowing streams via an external magnet, allowing polyelectrolyte deposition onto the cells immediately followed by the washing step, all in less than 90 s. This simple deposition technique shows promise for the functionalization of such cyborg cells for applications including bioelectronics, bioanalysis, and toxicity screening, while the addition of more reagent streams would enable the fabrication of multilayered capsules.
Research Interests:
The need for fast, specific and portable diagnostic systems for clinical assays has, in recent years, led to an explosion of research into microfluidic chip-based immunoassays towards rapid point-of-care analysis. Such devices exploit... more
The need for fast, specific and portable diagnostic systems for clinical assays has, in recent years, led to an explosion of research into microfluidic chip-based immunoassays towards rapid point-of-care analysis. Such devices exploit small dimensions, superior fluidic control and low reagent volumes to allow a number of clinically important procedures to be achieved with improvements on conventional methods, many of which rely on the surface-based binding of antigens to antibodies. Here, we discuss recent developments and innovations in the area of on-chip surface-based immunoassays and provide an outlook on the potential of such platforms for future diagnostics.
Research Interests:
We present temperature control as a simple yet highly efficient means of improving particle separations in on-chip free-flow magnetophoresis. Increased temperatures resulted in a decrease in solution viscosity, which in turn yielded... more
We present temperature control as a simple yet highly efficient means of improving particle separations in on-chip free-flow magnetophoresis. Increased temperatures resulted in a decrease in solution viscosity, which in turn yielded greater particle deflection distances and increased the separation resolution of two particle populations. This inexpensive and effective technique would also be of great benefit to other continuous flow processes involving the deflection of particles.
We have developed a magnetic particle-based assay platform in which functionalised magnetic particles are transferred sequentially through laminated volumes of reagents and washing buffers. Lamination of aqueous liquids is achieved via... more
We have developed a magnetic particle-based assay platform in which functionalised magnetic particles are transferred sequentially through laminated volumes of reagents and washing buffers. Lamination of aqueous liquids is achieved via the use of phaseguide technology; microstructures that control the advancing air–liquid interface of solutions as they enter a microfluidic chamber. This allows manual filling of the device, eliminating the need for external pumping systems, and preparation of the system requires only a few minutes. Here, we apply the platform to two on-chip strategies: (i) a one-step streptavidin–biotin binding assay, and (ii) a two-step C-reactive protein immunoassay. With these, we demonstrate how condensing multiple reaction and washing processes into a single step significantly reduces procedural times, with both assay procedures requiring less than 8 seconds.
Research Interests:
The continuous flow focussing and manipulation of particles and cells are important factors in microfluidic applications for performing accurate and reproducible procedures downstream. Many particle focussing methods require complex... more
The continuous flow focussing and manipulation of particles and cells are important factors in microfluidic applications for performing accurate and reproducible procedures downstream. Many particle focussing methods require complex setups or channel designs that can limit the process and its applications. Here, we present diamagnetic repulsion as a simple means of focussing objects in continuous flow, based only on their intrinsic properties without the requirement of any label. Diamagnetic polystyrene particles were suspended in a paramagnetic medium and pumped through a capillary between a pair of permanent magnets, whereupon the particles were repelled by each magnet into the central axis of the capillary, thus achieving focussing. By investigating this effect, we found that the focussing was greatly enhanced with (i) increased magnetic susceptibility of the medium, (ii) reduced flow rate of the suspension, (iii) increased particle size, and (iv) increased residence time in the magnetic field. Furthermore, we applied diamagnetic repulsion to the flow focussing of living, label-free HaCaT cells.
Research Interests:
Superconducting magnets enable the study of high magnetic fields on materials and objects, for example in material synthesis, self-assembly or levitation experiments. The setups employed often lack in precise spatial control of the object... more
Superconducting magnets enable the study of high magnetic fields on materials and objects, for example in material synthesis, self-assembly or levitation experiments. The setups employed often lack in precise spatial control of the object of interest within the bore of the magnet. Microfluidic technology enables accurate manipulation of fluidic surroundings and we have investigated the integration of microfluidic devices into superconducting magnets to enable controlled studies of objects in high magnetic fields. Polymeric microparticles similar in size to biological cells were manipulated via diamagnetic repulsion. The particles were suspended in an aqueous paramagnetic medium of manganese (II) chloride and pumped into a microfluidic chip, where they were repelled in continuous flow by the high magnetic field. The extent of deflection was studied as a function of increasing (1) particle size, (2) paramagnetic salt concentration, and (3) magnetic field strength. Optimizing these parameters allowed for the spatial separation of two particle populations via on-chip free-flow diamagnetophoresis. Finally, preliminary findings on the repulsion of air bubbles are shown.
Research Interests:
We demonstrate a versatile microfluidic system for performing rapid, consecutive (bio)chemical reactions in continuous flow. Surface-functionalised magnetic microparticles are introduced into a chamber and pulled, via a magnet, across a... more
We demonstrate a versatile microfluidic system for performing rapid, consecutive (bio)chemical reactions in continuous flow. Surface-functionalised magnetic microparticles are introduced into a chamber and pulled, via a magnet, across a series of laminar flow streams containing different reagents, thus performing multiple sequential reactions on the particles' surface. Such a continuous flow method eliminates many of the inefficiencies associated with batch techniques, such as the time-consuming, laborious sequential reaction and washing steps, to yield a system that can perform analyses far more rapidly and with less reagent volume than conventional methods. This innovative device has been applied to a two-reaction step mouse IgG sandwich immunoassay and one-and two-reaction step DNA hybridisation assays, all of which were completed within one minute. These results pave the way for a multi-purpose microreactor that can perform a variety of analytical and synthetic processes.
We present on-chip continuous flow DNA hybridisation and chemical synthesis of peptides. All the necessary washing and reaction steps are achieved by pulling magnetic particles across laminar streams with processing times of < 1 minute.
Microfluidic devices have shown great potential for the production of positron emission tomography (PET) radiotracers, but most devices have focused only on the synthesis step of the procedure, typically neglecting the other important... more
Microfluidic devices have shown great potential for the production of positron emission tomography (PET) radiotracers, but most devices have focused only on the synthesis step of the procedure, typically neglecting the other important steps such as [18F]fluoride pre-concentration and radiotracer purification that could equally benefit from miniaturisation. Here, we demonstrate the development of microfluidic modules for the purification of PET radiotracers, particularly 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG), via the use of on-chip solid-phase extraction (SPE). In these initial tests, the SPE modules were able to yield [18F]FDG with up to 90% radiochemical purity, and methods are proposed for further increasing this value.
Research Interests:
We have developed an integrated microfluidic platform for producing 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) in continuous flow from a single bolus of radioactive isotope solution, with constant product yields achieved throughout the... more
We have developed an integrated microfluidic platform for producing 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) in continuous flow from a single bolus of radioactive isotope solution, with constant product yields achieved throughout the operation that were comparable to those reported for commercially available vessel-based synthesisers (40–80%). The system would allow researchers to obtain radiopharmaceuticals in a dose-on-demand setting within a few minutes. The flexible architecture of the platform, based on a modular design, can potentially be applied to the synthesis of other radiotracers that require a two-step synthetic approach, and may be adaptable to more complex synthetic routes by implementing additional modules. It can therefore be employed for standard synthesis protocols as well as for research and development of new radiopharmaceuticals.
Research Interests:
We demonstrate a versatile multilaminar flow microfluidic device in which magnetic particles are used as mobile supports for performing two important applications, namely (i) a clinically relevant sandwich immunoassay, and (ii)... more
We demonstrate a versatile multilaminar flow microfluidic device in which magnetic particles are used as mobile supports for performing two important applications, namely (i) a clinically relevant sandwich immunoassay, and (ii) polyelectrolyte coating of templates towards the fabrication of microcapsules for drug delivery applications. Furthermore, we demonstrate the use of a different force, diamagnetic repulsion, for deflecting polystyrene particles through a reagent stream with a view to performing multilaminar flow studies on diamagnetic material such as polymer particles and cells.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
... Sample 5'-gcc ttc aag agc cac gtc tct acc ttg aca gac ctc cag ccg tac atg cga cag ttc gtg g 61 mer 3B-mis 5'-gcc ttc aag agc cac gtc tct acc ttg aca gac ctc cag ccg tac atg cga atc ttc gtg g 61 mer ... Bio-electron., vol.... more
... Sample 5'-gcc ttc aag agc cac gtc tct acc ttg aca gac ctc cag ccg tac atg cga cag ttc gtg g 61 mer 3B-mis 5'-gcc ttc aag agc cac gtc tct acc ttg aca gac ctc cag ccg tac atg cga atc ttc gtg g 61 mer ... Bio-electron., vol. 23, pp. 945 951, (2008). [3] S. Peyman, A. Iles and N. Pamme. ...