Monika Czugala

A portable centrifugal analyser for liver function screening

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 the read-out of a 5-parameter liver assay panel (LAP) on a portable, easy-to-use, fast and cost-efficient centrifugal microfluidic analysis system (CMAS). Our unique, dissolvable-film based centrifugo-pneumatic 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 min 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 complies 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 to a centralised lab in Nigeria.

Integrating stimulus responsive materials and microfluidics: The key to next-generation chemical sensors

New generations of chemical sensors require both innovative (evolutionary) engineering concepts and (revolutionary) breakthroughs in the fundamental materials chemistry, such as the emergence of new types of stimuli responsive materials. In recent years, intensive research in those fields has brought interesting new concepts and designs for microfluidic flow control and sample handling that integrate high-quality engineering with new materials. In this article, we review the recent developments in this fascinating area of science, with particular emphasis on photoswitchable soft actuators and their incorporation into fluidic devices that are increasingly biomimetic in nature.

Portable integrated microfluidic analytical platform for the monitoring and detection of nitrite.

A wireless, portable, fully-integrated microfluidic analytical platform has been developed and applied to the monitoring and determination of nitrite anions in water, using the Griess method. The colour intensity of the Griess reagent nitrite complex is detected using a low cost Paired Emitter Detector Diode, while on-chip fluid manipulation is performed using a biomimetic photoresponsive ionogel microvalve, controlled by a white light LED. The microfluidic analytical platform exhibited very low limits of detection (34.0±0.1 μg L(-1) of NO2(-)). Results obtained with split freshwater samples showed good agreement between the microfluidic chip platform and a conventional UV-vis spectrophotometer (R(2)=0.98, RSD=1.93% and R(2)=0.99, RSD=1.57%, respectively). The small size, low weight, and low cost of the proposed microfluidic platform coupled with integrated wireless communications capabilities make it ideal for in situ environmental monitoring. The prototype device allows instrument operational parameters to be controlled and analytical data to be downloaded from remote locations. To our knowledge, this is the first demonstration of a fully functional microfluidic platform with integrated photo-based valving and photo-detection.

CMAS: fully integrated portable centrifugal microfluidic analysis system for on-site colorimetric analysis

A portable, wireless system capable of in situ reagent-based colorimetric analysis is demonstrated. The system is based on a reconfigurable low cost optical detection method employing a paired emitter detector diode device, which allows a wide range of centrifugal microfluidic layouts to be implemented. Due to the wireless communication, acquisition parameters can be controlled remotely and results can be downloaded in distant locations and displayed in real time. The stand-alone capabilities of the system, combined with the portability and wireless communication, provide the flexibility crucial for on-site water monitoring. The centrifugal microfluidic disc presented here is designed for nitrite detection in water samples, as a proof of principle. A limit of detection of 9.31 ppb, along with similar coefficients of correlation and precision, were obtained from the Centrifugal Microfluidic Analysis System compared with the same parameters measured using a UV-Vis spectrophotometer.

A wireless paired emitter detector diode device as an optical sensor for Lab-on-a-disc applications

Here we report on a novel optical sensing configuration for Lab-on-a-disc colorimetric analysis applications. The system employs a wireless paired emitter detector diode device (PEDD), which consists of two light emitting diodes (LEDs). One LED, forward biased, serves as the light source whereas the other, in reverse bias mode, serves as the light detector. A simple timer circuit is used to measure the time taken for the photocurrent generated by the emitter LED to discharge the detector LED from 5 V (logic 1) to 1.7 V (logic 0) to give a digital output directly. The light dependent discharging process has been deployed for the measurement of concentrations of colored solutions in a microfluidic platform. The PEDD sensor was validated versus standard optical detection systems showing close correlation and similar limits of detection to UV-VIS spectroscopy.

Photo-switchable microvalve in a reusable Lab-on-a-disc

This contribution describes for the first time the fabrication and the performance of a reversible ionogel microvalve in-situ photopolymerised into a reusable disc platform for fluid control. During storage and spinning, the swollen microvalve provides a permanent liquid barrier due to the special chemical characteristics of the ionogel. The microvalve is easy actuated using a white light LED allowing open of the channel at a desired time. The actuation mechanism is chemically reversible when an acid solution is provided to the microvalve. Here a perpendicular microchannel, connected to the valve from behind, is used to ensure the re-swelling of the ionogel and therefore reusability of the Lab-on-a-disc.