In this article we introduce a novel technology that utilizes specialized water dissolvable thin films for valving in centrifugal microfluidic systems. In previous work (William Meathrel and Cathy Moritz, IVD Technologies, 2007), dissolvable films (DFs) have been assembled in laminar flow devices to form efficient sacrificial valves where DFs simply open by direct contact with liquid. Here, we build on the original DF valving scheme to leverage sophisticated, merely rotationally actuated vapour barriers and flow control for enabling comprehensive assay integration with low-complexity instrumentation on "lab-on-a-disc" platforms. The advanced sacrificial valving function is achieved by creating an inverted gas-liquid stack upstream of the DF during priming of the system. At low rotational speeds, a pocket of trapped air prevents a surface-tension stabilized liquid plug from wetting the DF membrane. However, high-speed rotation disrupts the metastable gas/liquid interface to wet the DF and thus opens the valve. By judicious choice of the radial position and geometry of the valve, the burst frequency can be tuned over a wide range of rotational speeds nearly 10 times greater than those attained by common capillary burst valves based on hydrophobic constrictions. The broad range of reproducible burst frequencies of the DF valves bears the potential for full integration and automation of comprehensive, multi-step biochemical assay protocols. In this report we demonstrate DF valving, discuss the biocompatibility of using the films, and show a potential sequential valving system including the on-demand release of on-board stored liquid reagents, fast centrifugal sedimentation and vigorous mixing; thus providing a viable basis for use in lab-on-a-disc platforms for point-of-care diagnostics and other life science applications.

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Over the past two decades, centrifugal microfluidic systems have successfully demonstrated their capability for robust, high-performance liquid handling to enable modular, multi-purpose lab-on-a-chip platforms for a wide range of life-science applications. Beyond the handling of homogeneous liquids, the unique, rotationally controlled centrifugal actuation has proven to be specifically advantageous for performing cell and particle handling and assays. In this review we discuss technologies to implement two important steps for cell handling, namely separation and capturing/counting.

Mortality rates of up to 50% have been reported after liver failure due to drug-induced hepatotoxicity and certain viral infections (Gao et al. 2008). These adverse conditions frequently affect HIV and tuberculosis patients on regular medication in resource-poor settings. Here, we report full integration of sample preparation with read-out of a 5-parameter liver assay panel (LAP) on a portable, easy-to-use, fast and costefficient centrifugal microfluidic analysis system (CMAS). Our unique, dissolvable-film based centrifugopneumatic valving was employed to provide sample-to-answer fashion automation for plasma extraction (from finger-prick of blood), metering and aliquoting into separate reaction chambers for parallelized colorimetric quantification during rotation. The entire LAP completes in less than 20 minutes while using only a tenth the reagent volumes when compared with standard hospital laboratory tests. Accuracy of in-situ liver function screening was validated by 96 separate tests with an average coefficient of variance (CV) of 7.9% compared to benchtop and hospital lab tests. Unpaired two sample statistical t-tests were used to compare the means of CMAS and benchtop reader, on one hand; and CMAS and hospital tests on the other. The results demonstrate no statistical difference between the respective means with 94% and 92% certainty of equivalence, respectively. The portable platform thus saves significant time, labour and costs compared to established technologies, and therefore comply with typical restrictions on lab infrastructure, maintenance, operator skill and costs prevalent in many field clinics of the developing world. It has been successfully deployed in a centralised lab in Nigeria. IntroductionLiver is the largest solid organ in the body and is largely responsible for metabolism and detoxification. (Gao et al. 2008) Liver function tests are widely used in clinical chemistry to assess therapeutic effects and potential medication-induced liver damage, especially when taking medications for HIV, tuberculosis and cancer. (Landis et al. 2013;Rahmioglu et al. 2009; Vella et al. 2012) Literature reports suggest that a mortality rate of 2 -28% can be linked with medication-induced liver damage. (Vella et al. 2012) As a result, monitoring of liver function when on certain medications has become common practice in developed countries but can be expensive in poor resource areas. This has prompted local governments and international funding agencies to set up centralised laboratories for liver function monitoring tests especially for HIV patients. Nonetheless, transport logistics and accessibility remains a significant challenge for the majority of these patients. Thus it is very important to develop portable point-of-care (PoC) devices that could be used for liver function screening in the field. Currently, there are only a handful of sample-to-answer PoC devices available for deployment in the field. Recently, Vella et al.(Vella et al. 2012) demonstrated an innovative micropatterned paper device fo...

Plasma diagnostics of atmospheric plasmas is a key tool in helping to understand processing performance issues. This paper presents an electrical, optical and thermographic imaging study of the PlasmaStream atmospheric plasma jet system. The system was found to exhibit three operating modes; one constricted/localized plasma and two extended volume plasmas. At low power and helium flows the plasma is localized at the electrodes and has the electrical properties of a corona/filamentary discharge with electrical chaotic temporal structure. With increasing discharge power and helium flow the plasma expands into the volume of the tube, becoming regular and homogeneous in appearance. Emission spectra show evidence of atomic oxygen, nitric oxide and the hydroxyl radical production. Plasma activated gas temperature deduced from the rotational temperature of nitrogen molecules was found to be of order of 400 K: whereas thermographic imaging of the quartz tube yielded surface temperatures between 319 and 347 K.

Surfaces with water contact angles above 150° are regarded as superhydrophobic. In this study the use of atmospheric pressure plasma jet system called PlasmaStreamTM to deposit superhydrophobic coatings is investigated. The coatings were deposited from the following liquid precursors: hexamethyldisiloxane (HMDSO), tetramethyl cyclotetrasiloxane (Tomcats) and a mixture of Tomcats and fluorosiloxane. The objective of the study is to investigate how precursor type and deposition conditions, influences the morphology and mechanical performance of the deposited superhydrophobic coatings. Optical profilometry, AFM, SEM, Ellipsometry, XPS, Water contact angle and FTIR techniques were used to evaluate the surface roughness, morphology, thickness and chemical functionality of the deposited coatings. The mechanical properties were evaluated using the Nano Tribometer, Nano Scratch, Ultra Nanoindentation and ultrasonic abrasion tests. Superhydrophobic coatings deposited from a precursor mixture of Tomcats and fluorosiloxane yielded a substantial enhancement in coating adhesion and mechanical durability compared to the superhydrophobic coatings obtained with either Tomcats or HMDSO precursors alone.

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BACKGROUND: Silicone elastomers have outstanding material properties including good thermal stability, low electrical conductivity, biocompatibility and resilient physical and chemical properties. These elastomers, however, exhibit relatively poor adhesion to stainless steel, and the use of a nanometre thick plasma‐polymerised primer layer as a means of enhancing this adhesion was investigated in this study. The primer coatings studied consisted of polyhydrogenmethylsiloxane (PHMS), tetraethyl orthosilicate (TEOS) and mixtures of these two liquid precursors. RESULTS: The plasma‐polymerised primer coatings were deposited onto stainless steel substrates using a PlasmaStream™ atmospheric pressure plasma jet system. Deposited coatings were examined using ellipsometry, contact angle measurements, optical profilometry, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy. The adhesion of silicone elastomers bonded to the primed and bare stainless steel surfaces was assessed using 45° adhesion strength measurements. Elastomer adhesion was correlated with surface energy, thickness and roughness. CONCLUSION: An up to 15‐fold increase in adhesive fracture energy was observed for silicone elastomers bonded to the primed versus untreated stainless steel. The highest adhesion was observed for a coating deposited from a PHMS‐to‐TEOS precursor molar ratio of 3 to 1. Copyright © 2009 Society of Chemical Industry