Fully integrated digital microfluidics platform for automated immunoassay; a versatile tool for rapid, specific detection of a wide range of pathogens

© 2018 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/.With the tangible threat posed by the release of chemical and biological warfare (CBW) agents, detection of airborne pathogens is a critical military and security concern. Recent air sampling techniques developed for biocollection take advantage of Electrowetting on Dielectric (EWOD) to recover material, producing highly concentrated droplet samples. Bespoke EWOD-based digital microfluidics platforms are very well suited to take full advantage of the microlitre concentrated droplet resulting from this recovery process. In this paper we present a free-standing, fully automated DMF platform for immunoassay. Using this system, we demonstrate the automated detection of four classes of CBW agent simulant biomolecules and organisms each representing credible threat agents. Taking advantage of the full magnetic separation process with antibody-bound microbeads, rapid and complete separation of specific target antigen can be achieved with minimal washing steps allowing for very rapid detection. Here, we report clear detection of four categories of antigens achieved with assay completion times of between six and ten minutes. Detection of HSA, Bacillus atrophaeus (BG spores), MS2 bacteriophage and Escherichia coli are demonstrated with estimated limit of detection of respectively 30 ng ml -1, 4 × 10 4 cfu ml -1, 10 6 pfu ml -1 and 2 × 10 7 cfu ml -1. The fully-integrated portable platform described in this paper is highly compatible with the next generation of electrowetting-coupled air samplers and thus shows strong potential toward future in-field deployable biodetection systems and could have key implication in life-changing sectors such as healthcare, environment or food security.Peer reviewe

Electrowetting-Based Digital Microfluidics Platform for Automated Enzyme-linked Immunosorbent Assay

Electrowetting is the effect by which the contact angle of a droplet exposed to a surface charge is modified. Electrowetting-on-dielectric (EWOD) exploits the dielectric properties of thin insulator films to enhance the charge density and hence boost the electrowetting effect. The presence of charges results in an electrically induced spreading of the droplet which permits purposeful manipulation across a hydrophobic surface. Here, we demonstrate EWOD-based protocol for sample processing and detection of four categories of antigens, using an automated surface actuation platform, via two variations of an Enzyme-Linked Immunosorbent Assay (ELISA) methods. The ELISA is performed on magnetic beads with immobilized primary antibodies which can be selected to target a specific antigen. An antibody conjugated to HRP binds to the antigen and is mixed with H 2O 2/Luminol for quantification of the captured pathogens. Assay completion times of between 6 and 10 min were achieved, whilst minuscule volumes of reagents were utilized.Peer reviewe

Intermixing of InGaAs/GaAs quantum wells and quantum dots using sputter-deposited silicon oxynitride capping layers

Various approaches can be used to selectively control the amount of intermixing in III-Vquantum well and quantum dotstructures. Impurity-free vacancy disordering is one technique that is favored for its simplicity, however this mechanism is sensitive to many experimental parameters. In this study, a series of silicon oxynitride capping layers have been used in the intermixing of InGaAs/GaAs quantum well and quantum dotstructures. These thin films were deposited by sputter deposition in order to minimize the incorporation of hydrogen, which has been reported to influence impurity-free vacancy disordering. The degree of intermixing was probed by photoluminescence spectroscopy and this is discussed with respect to the properties of the SiOxNyfilms. This work was also designed to monitor any additional intermixing that might be attributed to the sputtering process. In addition, the high-temperature stress is known to affect the group-III vacancy concentration, which is central to the intermixing process. This stress was directly measured and the experimental values are compared with an elastic-deformation model.This work has been made possible with access to the ACT Node of the Australian National Fabrication Facility and through the financial support of the Australian Research Council

Towards Effective Low-bitwidth Convolutional Neural Networks

This paper tackles the problem of training a deep convolutional neural network with both low-precision weights and low-bitwidth activations. Optimizing a low-precision network is very challenging since the training process can easily get trapped in a poor local minima, which results in substantial accuracy loss. To mitigate this problem, we propose three simple-yet-effective approaches to improve the network training. First, we propose to use a two-stage optimization strategy to progressively find good local minima. Specifically, we propose to first optimize a net with quantized weights and then quantized activations. This is in contrast to the traditional methods which optimize them simultaneously. Second, following a similar spirit of the first method, we propose another progressive optimization approach which progressively decreases the bit-width from high-precision to low-precision during the course of training. Third, we adopt a novel learning scheme to jointly train a full-precision model alongside the low-precision one. By doing so, the full-precision model provides hints to guide the low-precision model training. Extensive experiments on various datasets ( i.e., CIFAR-100 and ImageNet) show the effectiveness of the proposed methods. To highlight, using our methods to train a 4-bit precision network leads to no performance decrease in comparison with its full-precision counterpart with standard network architectures ( i.e., AlexNet and ResNet-50).Comment: 11 page

Electromagnetic Actuated Stiring in Microbioreactor Enabling Easier Multiplexing and Flexible Device Design

The development of a novel electromagnetically (EM) actuated stirring method, for use in microbioreactors, is reported. Mixing in microbioreactors is critical to ensure even distribution of nutrients to microorganisms and cells. Magnetically driven stirrer bars or peristaltic mixing are the most commonly utilised mixing methods employed in completely liquid-filled microbioreactors. However the circular reactor shape required for mixing with a stirrer bar and frequently used for peristaltically mixed microbioreactors presents difficulties for bubble-free priming in a microfluidic bioreactor. Moreover the circular shape and the hardware required for both types of mixing reduces the potential packing density of multiplexed reactors. We present a new method of mixing, displaying design flexibility by demonstrating mixing in circular and diamond-shaped reactors and a duplex diamond reactor and fermentation of the gram-positive bacteria S. carnosus in a diamond-shaped microbioreactor system. The results of the optimisation of this mixing method for performing fermentations alongside both batch and continuous culture fermentations are presentedPeer reviewe

Dean flow focusing and separation of small microspheres within a narrow size range.

Copyright The Author(s) 2014. This article is published with open access at Springerlink.com. This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are creditedRapid, selective particle separation and concentration within the bacterial size range (1–3 μm) in clinical or environmental samples promises significant improvements in detection of pathogenic microorganisms in areas including diagnostics and bio-defence. It has been proposed that microfluidic Dean flow-based separation might offer simple, efficient sample clean-up: separation of larger, bioassay contaminants to prepare bioassay targets including spores, viruses and proteins. However, reports are limited to focusing spherical particles with diameters of 5 μm or above. To evaluate Dean flow separation for (1–3 μm) range samples, we employ a 20 μm width and depth, spiral microchannel. We demonstrate focusing, separation and concentration of particles with closely spaced diameters of 2.1 and 3.2 μm, significantly smaller than previously reported as separated in Dean flow devices. The smallest target, represented by 1.0 μm particles, is not focused due to the high pressures associated with focussing particles of this size; however, it is cleaned of 93 % of 3.2 μm and 87 % of 2.1 μm microparticles. Concentration increases approaching 3.5 times, close to the maximum, were obtained for 3.2 μm particles at a flow rate of 10 μl min−1. Increasing concentration degraded separation, commencing at significantly lower concentrations than previously predicted, particularly for particles on the limit of being focused. It was demonstrated that flow separation specificity can be fine-tuned by adjustment of output pressure differentials, improving separation of closely spaced particle sizes. We conclude that Dean flow separation techniques can be effectively applied to sample clean-up within this significant microorganism size range.Peer reviewedFinal Published versio

Imagine staying in a Shanghai hotel bedroom in 2050?

Will the future hotels of Shanghai emphasise a world of contemporary design, sustainability and technological innovations in order to deal with the growing pains of pollution, competition of urban land and decreasing availability of clean water, which will impact on the quality and price of accommodation in  the city? This paper imagines what a hotel might look like in 2050 based upon nine drivers of change, whether it is new sciences such as claytronics, or programmable matter that integrate sight, sound and feel into original ideas, allowing users to interact with three-dimensional form. The applications of claytronics would be the reconfiguration of everything, so just imagine the future hotel bed that could change its degree of comfort from a hard to a soft mattress without too much effort, the possibilities are endless. Other drivers include robotics as an alternative to a human labour supply or the behaviours of  Generation Y. The heart to the future is sustainable design and this paper discusses how the hotel will feature many of these changes in a future world in order to mitigate and adapt to a paradigm of scarcity of resources.Keywords: drivers of change, future hotels, innovations, sustainability, sustainable designResearch in Hospitality Management 2012, 1(2): 85–9

Enzyme Encapsulation by Static Mixer Method for Hydrolysis of Lactose

Enzyme immobilisation has been intensively investigated due to its advantages such as enzyme recovery, reusability and improved stability over a wide range of pH and temperatures. The encapsulation of beta-galactosidase in kappa-carrageenan is presented in this report for potential application in dairy industry. The immobilisation was carried out by emulsifying oil and kappa-carrageenan with a static mixer device. This is a new approach and has the advantage of producing smaller beads (e.g. smaller than 100 µm size) which can be used in continuous processing. The main factors tested were the total flow rate through the static mixer (etta, in the range 220 - 440 ml/min) and kappa-carrageenan to oil volumetric fraction (Qt, in the range 0.05-0.2). The average bead sizes obtained were in the range of 19 - 52 µm, with smaller sizes obtained with an increase of Qt. The bead sizes decreased with (i) the decrease in emulsified droplets coalescence and oil inclusion in the beads and (ii) with the decrease in the values of WGtop (defined by the weight percentage of beads found underneath the oil layer). The bead performance was tested using lactose and 2-nitrophenyl-beta-galactopyranoside (ONPG) and the kinetic parameters, lactose conversion and stability were determined at the optimum conditions. The attained optimum pH and temperature were 7 (similar to free enzyme) and 21oC, respectively. The encapsulated beta-galactosidase tested at optimum conditions in 5% (w/v) lactose solution was able to convert 76.47% of lactose after six days. These findings contribute to the further understanding of the encapsulation technique and demonstrates the potential of using kappa-carrageenan as an encapsulation material for beta-galactosidase