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The ability to detect radiation in microfluidic devices is important for the on-chip analysis of radiopharmaceuticals, but previously reported systems have largely suffered from various limitations including cost, complexity of fabrication, and insufficient sensitivity and/or speed. Here, we present the use of sensitive, low cost, small-sized, commercially available silicon photomultipliers (SiPMs) for the detection of radioactivity inside microfluidic channels fabricated from a range of conventional microfluidic chip substrates. We demonstrate the effects of chip material and thickness on the detection of the positron-emitting isotope, [(18)F]fluoride, and find that, while the SiPMs are light sensors, they are able to detect radiation even through opaque chip materials via direct positron and gamma (γ) ray interaction. Finally, we employed the SiPM platform for analysis of the PET (positron emission tomography) radiotracers 2-[(18)F]fluoro-2-deoxy-d-glucose ([(18)F]FDG) and [(68)Ga]gallium-citrate, and highlight the ability to detect the γ ray emitting SPECT (single photon emission computed tomography) radiotracer, [(99m)Tc]pertechnetate.

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. Microgels are micrometer sized particles consisting of a polymer network that show potential for the delivery of both hydrophilic and hydrophobic drugs. Microfluidic devices provide an excellent format for the generation of monodispersed droplets due to the precise manipulation of fluids and flow rates within the microchannels. Microfluidic droplet generation chips were therefore designed using T-junction and flow focusing geometries in glass. For microgel synthesis, monomers, crosslinker and initiator were added to the dispersed phase and water was used as the continuous phase. Controlled formation of monodisperse droplets was achieved with both geometries and droplets were collected off-chip for photopolymerisation. Three types of microgel were formed using this setup: poly(ethylene glycol) diacrylate, poly(propylene glycol) diacrylate, and tetrahydropyran acrylate - ethylene glycol dimethacrylate (THPA-EGDMA) microgels. THPA is a novel material for microgels that can be turned from hydrophobic to amphiphilic by hydrolysation. THPA-EGDMA microgels in particular demonstrated a strong response to pH changes due to the build-up of electrostatic force under high pH, showing potential for the encapsulation and release of drugs.

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. © 2013 Elsevier B.V.

There is an increasing demand for easy and cost-effective methods to screen the toxicological impact of the growing number of chemical mixtures being generated by industry. Such a screening method has been developed using viable, genetically modified green fluorescent protein (GFP) reporter yeast that was magnetically functionalised and held within a microfluidic device. The GFP reporter yeast was used to detect genotoxicity by monitoring the exposure of the cells to a well-known genotoxic chemical (methyl methane sulfonate, MMS). The cells were magnetised using biocompatible positively charged PAH-stabilised magnetic nanoparticles with diameters around 15 nm. Gradient mixing was utilised to simultaneously expose yeast to a range of concentrations of toxins, and the effective fluorescence emitted from the produced GFP was measured. The magnetically enhanced retention of the yeast cells, with their facile subsequent removal and reloading, allowed for very convenient and rapid toxicity screening of a wide range of chemicals. This is the first report showing magnetic yeast within microfluidic devices in a simple bioassay, with potential applications to other types of fluorescent reporter yeast in toxicological and biomedical research. The microfluidic chip offers a simple and low-cost screening test that can be automated to allow multiple uses (adapted to different cell types) of the device on a wide range of chemicals and concentrations. © 2010 Springer-Verlag.

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications. 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. This study is funded by the Engineering and Physical Sciences Research Council (EPSRC).

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications. Free-flow magnetophoresis provides a fast and efficient means of continuous flow magnetic separation for the detection of biological analytes, due to the wide variety of magnetic particle surface properties available for binding specific targets. Here, we investigate the effect of temperature changes on the deflection behaviour of magnetic particles in a microfluidic magnetophoresis separation chamber. It was found that the extent of deflection was greatly increased at higher temperatures due to decreased solution viscosity and thus reduced resistance against particle motion. This concept was used to improve the resolution of the separation of 2.8 μm and 1 μm diameter magnetic particles. Hence, controlling the temperature of the separation system provides a simple but highly effective means of enhancing magnetic separation efficiency. This concept could also be applied to the temperature-based tuning of microparticle trajectories in many others types of continuous flow processes, such as those using optical, electrical or acoustic forces. This study is funded by the Engineering and Physical Sciences Research Council (EPSRC).

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications. The continuous flow generation and downstream manipulation of magnetic droplets inside a microfluidic device was investigated. Magnetic droplets were generated from aqueous ferrofluids in organic oil phase using T-junction and flow-focusing geometries in glass microfluidic devices. Due to the hydrophilic nature of glass surfaces, it was necessary to apply a hydrophobic coating in the form fluorocarbons. The size of the magnetic droplets and distance between them were controlled by adjusting the relative flow velocities of ferrofluid and oil carrier liquid. Two modes of droplet manipulation were investigated by placing small permanent magnets in the vicinity of the microfluidic channels: (i) droplet deflection across a flow chamber which could be used for sorting of droplets based on the magnetic field applied and (ii) droplet splitting at a branching junction resulting in two daughter droplets of high and low magnetite content. This study is funded by The University of Kuwait.