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

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

The Design of an Innovative Research Led, Undergraduate Programme for Effective Development of R&D Skills and Learning.

Daniel McCluskey, Christabel Tan, Mark Tracey, Ian Johnston, Loic Coudron, ‘The Design of an Innovative Research Led, Undergraduate Programme for Effective Development of R&D Skills and Learning’, paper presented at the 1st ASEAN Innovation Conference, Vientiane, Lao People’s Democratic Republic, 25-26 October, 2016.Engineering education has suffered a shift in focus between research led fundamental engineering and vocational training that has resulted in many graduate engineers equipped without a thorough grasp of either skill set. Furthermore the belief that these two components of education can be explicitly separated appears to undermine the notion of what a graduate engineer is. The purpose of this paper is to outline the development of a research informed, undergraduate, module that incorporates the principles of the Massachusetts Institute of Technology developed approach to engineering education where the core components of study are formed around the concept of CDIO (Conceive, Design, Implement, Operate). We outline our initial starting concept for the taught module and systematically break down the CDIO approach, applying the outcomes of this process to the design of the engineering module. The resultant module structure incorporates the majority of the CDIO principles, and highlights the mechanisms by which research can inform undergraduate teaching without straying away from the development of practical skills required by the graduate engineer. This work suggests that the CDIO approach, with minor modification, can be tailored to a single isolated module structure as well as a whole curriculum provided that there is a clear objective outlined at the start

Protein droplet actuation on superhydrophobic surfaces: A new approach toward anti-biofouling electrowetting systems

© 2017 The Royal Society of Chemistry. This is an Open Access article, distributed under the terms of the Creative Commons Attribution 3.0 Unported (CC BY 3.0) licence https://creativecommons.org/licenses/by/3.0/.Among Lab-on-a-chip techniques, Digital microfluidics (DMF), allowing the precise actuation of discrete droplets, is a highly promising, flexible, biochemical assay platform for biomedical and bio-detection applications. However the durability of DMF systems remains a challenge due to biofouling of the droplet-actuating surface when high concentrations of biomolecules are employed. To address this issue, the use of superhydrophobic materials as the actuating surface in DMF devices is examined. The change in contact angle by electrowetting of deionised water and ovalbumin protein samples is characterised on different surfaces (hydrophobic and superhydrophobic). Ovalbumin droplets at 1 mg ml-1 concentration display better electrowetting reversibility on Neverwet®, a commercial superhydrophobic material, than on Cytop®, a typical DMF hydrophobic material. Biofouling rate, characterised by roll-off angle measurement of ovalbumin loaded droplets and further confirmed by measurements of the mean fluorescence intensity of labelled fibrinogen, appears greatly reduced on Neverwet®. Transportation of protein laden droplets (fibrinogen at concentration 0.1 mg ml-1 and ovalbumin at concentration 1 mg ml-1 and 10 mg ml-1) is successfully demonstrated using electrowetting actuation on both single-plate and parallel-plate configurations with performance comparable to that of DI water actuation. In addition, although droplet splitting requires further attention, merging and efficient mixing are demonstrated.Peer reviewe

Controlled Actuation of Self-Propelled Droplets

© 2020, University of Hertfordshire.In this paper we present controlled self-propelled actuation of droplets employing Laplace pressure gradients between two non-parallel superhydrophobic plates. For small angles (cos β ≈ 1) a simplification of available energy-based models can accurately predict the droplets initial acceleration. By adjusting the plates’ spacing and angle (from 0.2° to 1.5°), the value of the droplets initial acceleration can be varied from 0.28 m s^-2 to 3.9 m s^-2 hence showing significant promise for precise controlled actuation. Such an actuation principle could find applications within droplet-based lab-on-a-chip systems where superhydrophobic surfaces could help address the challenges of transporting biomaterial laden droplets.Peer reviewe