1,720,975 research outputs found
Integrated optical microflow cytometer for bead-based immunoassays
Full text linkFlow cytometry is an important tool for medicine and biology with applications from clinical diagnosis to investigations of fundamental cell biology. However, traditional flow cytometers are expensive, bulky and complex to operate. Miniaturised flow cytometers or microflow cytometers offer advantages over traditional devices, being compact, cheap and mass producible and would offer the user ease of operation and low sample consumption. A key challenge for developing a microflow cytometer is the integration of the optical components with the fluidics. Integrated optical waveguides offer an ideal method of light control in microflow cytometers as the waveguides are intrinsically aligned to the analysis region during fabrication.In this thesis the design, fabrication and demonstration of a silica-based microflow cytometer for bead-based immunoassays is presented. The device consists of a rugged monolithic glass chip with integrated waveguides which deliver excitation light to an etched microfluidic channel and collect light transmitted across the channel. The fluidics are designed to employ inertial focusing to reduce signal variation by bringing the flowing beads onto the same plane as the excitation beam.A fabrication process was developed using techniques common to the microelectronics industry which are scalable for mass production. This process allowed the realisation of devices with waveguides of a range of widths from 2.0 µm and upwards allowing both single mode and multimode operation at the immunoassay analysis wavelengths of 532 nm and 637 nm. Microfluidic channels with rectangular cross sections suitable for inertial focussing with depths of 30 µm were also realised.Inertial focussing was demonstrated to confine the flowing beads in two dimensions in the microfluidic channel which effectively reduced the fluorescence signal variation in the device to a CV of 29%. The application of the device was demonstrated by the detection of fluorescence from immunoassay beads incubated with the cytokine tumour necrosis factor α at 154 pg/ml. Additional functionality of the device was demonstrated with transmission based detection of flowing beads
Data set For : A light-guiding urinary catheter for the inhibition of Proteus mirabilis biofilm formation
No full textData set for Journal publication in Frontiers in Microbiology.
Data includes
- Characterisation of light guiding catheters
- Dose response relationship between irradiance and anti biofilm effect for Proteus Mirabilis (PM)
- SEM images of effect of blue light on PM biofilm formation.
-Microbiological evaluation of light guiding catheters</span
Serial integration of Dean-structured sample cores with linear inertial focussing for enhanced particle and cell sorting
No full textIn this contribution, a channel aspect ratio of >2 was used to access high velocity regimes to provide confined sample cores by Dean focussing in advance of linear inertial focussing. This produces a singular separation origin with a mirrored transport path for efficient particle and blood cell sorting, while also increasing the spatial resolution for multiscale sorting.</p
Laser-based printing and patterning for biological applications
No full textWe present the use of pulsed lasers as patterning and printing tools for the end applications of micro-contact printing and paper-based fluidics. A fs-laser was used with a digital multi-mirror device (DMD) to structure a mould via ablation or photo-polymerisation. The patterns in this mould were then cast into polydimethlysiloxane (PDMS)-mould which was used for micro-contact printing. With the end-goal of producing a microfluidic diagnostic sensor on paper, a ns-laser was used for laser-induced forward transfer (LIFT) of proteins onto a paper substrate, whose viability was validated by a colorimetric detection assa
Mask-less laser-machining for rapid low-cost patterning of microstructures in polydimethylsiloxane (PDMS)
No full textWe report on the use of a mask-less laser-machining procedure that enables the rapid creation of micron-scale structures in polydimethylsiloxane (PDMS), a platform most commonly used in the implementation of lab-on-chip devices, and also in micro-contact printing or soft lithography. The designed two-dimensional array of structures, extending over ~1mm2 regions with micron-scale resolution, was laser-ablated into a thin film through the use of femtosecond laser pulses (150fs, 800nm) that were spatially shaped via diffraction from a programmable digital multi-mirror device (DMD). The high switching speed of the DMD mirrors in combination with a high repetition rate laser provides the ability to pattern any desired 2D prototype on the ~1mm scale within a few minutes, circumventing the need for a custom-designed mask and photolithography which is generally needed to produce a specific prototyping master mould. The complementary pattern from the thin film was subsequently transferred into PDMS for fabrication of a mould that was used for micro-contact printing of ink onto a glass substrate. In addition, this non-lithographic, mask-less laser-machining approach can be extended to form both complex micron and submicron scale structures that are useful in contact printing applications but also in the fabrication of millimetre scale lab-on-chip fluidic device
Dataset supporting the publication "Discrimination of microplastics and phytoplankton using impedance cytometry"
No full textDataset supporting the publication "Discrimination of microplastics and phytoplankton using impedance cytometry", ACS sensors.
Dataset includes the impedance flow cytometry data of microplastic and phytoplanton samples.
The data is accessible under CC- BY- NC license</span
Perpetual sedimentation for the continuous delivery of particulate suspensions
No full textParticle sedimentation is deleterious to a tremendous variety of microfluidic applications. Here we show that syringe rotation retains particles in a suspended state, providing a universal solution for the continuous delivery of particulate samples to microfluidic processors
Data_Sheet_1_A light-guiding urinary catheter for the inhibition of Proteus mirabilis biofilm formation.PDF
No full textCatheter-associated urinary tract infection (CAUTI) is a leading cause of hospital-acquired infections worldwide causing debilitating illness for patients as well as a significant financial and treatment burden on health services. CAUTI is linked with the build-up of biofilms on catheter surfaces which act as a reservoir for infection. Additionally, urease-producing bacteria such as Gram-negative Proteus mirabilis (PM), can form crystalline biofilms which encrust catheter surfaces ultimately leading to blockages which require immediate removal of the catheter. Currently there are limited treatments available to prevent the formation of biofilms by PM as well as other urinary tract infection causing bacteria. A novel concept for a light-guiding urinary catheter is presented where a silicone elastomer waveguide incorporated along the length of the catheter is used to irradiate the catheter surfaces with antimicrobial blue light (405 nm) to prevent biofilm formation in situ. The prototype device is mass producible while also easy to fabricate in a lab setting for research studies. The inhibitory effect of blue light on PM biofilm formation over a range of irradiances is described for the first time showing an LD90 at 192–345 J/cm2 and total inhibition at 1,700 J/cm2In vitro studies show that the light-guiding catheter (LGC) prototypes exhibit a 98% inhibition in PM biofilm formation inside the catheter lumen at an average estimated irradiance of 30–50 mW/cm2 (324–540 J/cm2 fluence) showing that the concept is highly effective, promising to be a powerful and economical antimicrobial approach to prevent catheter associated biofilm development and blockage.</p
Discrimination of microplastics and phytoplankton using impedance cytometry
Full text linkABSTRACT: Both microplastics and phytoplankton are found together in the ocean as suspended microparticles. There is a need for deployable technologies that can identify, size, and count these particles at high throughput to monitor plankton community structure and microplastic pollution levels. In situ analysis is particularly desirable as it avoids the problems associated with sample storage, processing, and degradation. Current technologies for phytoplankton and microplastic analysis are limited in their capability by specificity, throughput, or lack of deployability. Little attention has been paid to the smallest size fraction of microplastics and phytoplankton below 10 μm in diameter, which are in high abundance. Impedance cytometry is a technique that uses microfluidic chips with integrated microelectrodes to measure the electrical impedance of individual particles. Here, we present an impedance cytometer that can discriminate and count microplastics sampled directly from a mixture of phytoplankton in a seawater-like medium in the1.5−10 μm size range. A simple machine learning algorithm was used to classify microplastic particles based on dual-frequency impedance measurements of particle size (at 1 MHz) and cell internal electrical composition (at 500 MHz). The technique shows promise for marine deployment, as the chip is sensitive, rugged, and mass producible
Monolithically-integrated cytometer for measuring particle diameter in the extracellular vesicle size range using multi-angle scattering
Full text linkSize measurement of extracellular vesicles is hampered by the high cost and measurement uncertainty of conventional flow cytometers which is mainly due to the use of non-specialised free space optics. Integrated cytometry, where the optics and fluidics are embedded in a monolithic chip shows promise for the production of low cost, micro-flow cytometers dedicated for extracellular vesicle (EV) analysis with improved size measurement accuracy and precision. This research demonstrates a unique integrated cytometer for sub-micron particle size measurement using multi-angle scattering analysis. A combination of three technologies is used: (i) Dean-based hydrodynamic focussing to deliver a tight sample core stream to the analysis region, (ii) integrated waveguides with multimode interference devices to focus a narrow excitation beam onto the sample stream, and (iii) an angular array of collection waveguides to measure particle scattering distribution and calculate diameter. Low index 200 nm liposomes could be detected and polystyrene size standards as small as 400 nm diameter could be measured with an uncertainty of ± 21 nm (1/2 IQR) demonstrating a first step on the path to high performance integrated cytometry of EVs
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