Jennifer Gaughran

Fluidic Automation of Nitrate and Nitrite Bioassays in Whole Blood by Dissolvable-Film Based Centrifugo-Pneumatic Actuation

This paper demonstrates the full centrifugal microfluidic integration and automation of all liquid handling steps of a 7-step fluorescence-linked immunosorbent assay (FLISA) for quantifying nitrate and nitrite levels in whole blood within about 15 min. The assay protocol encompasses the extraction of metered plasma, the controlled release of sample and reagents (enzymes, co-factors and fluorescent labels), and incubation and detection steps. Flow control is implemented by a rotationally actuated dissolvable film (DF) valving scheme. In the valves, the burst pressure is primarily determined by the radial position, geometry and volume of the valve chamber and its inlet channel and can thus be individually tuned over an extraordinarily wide range of equivalent spin rates between 1,000 RPM and 5,500 RPM. Furthermore, the vapour barrier properties of the DF valves are investigated in this paper in order to further show the potential for commercially relevant on-board storage of liquid reagents during shelf-life of bioanalytical, ready-to-use discs.

Phase-selective graphene oxide membranes for advanced microfluidic flow control

For the first time, we harness the unique phase-selectivity of chip-integrated graphene oxide (GO) membranes to significantly enhance flow control on centrifugal microfluidic platforms. In this paper, we present novel processes for the assembly of these GO membranes into polymeric microfluidic systems and demonstrate that multilayer GO membranes allow the passage of water while blocking pressurized air and organic solutions.

Identification of sleep apnea events using discrete wavelet transform of respiration, ECG and accelerometer signals

Sleep apnea is a common sleep disorder in which patient sleep patterns are disrupted due to recurrent pauses in breathing or by instances of abnormally low breathing. Current gold standard tests for the detection of apnea events are costly and have the addition of long waiting times. This paper investigates the use of cheap and easy to use sensors for the identification of sleep apnea events. Combinations of respiration, electrocardiography (ECG) and acceleration signals were analysed. Results show that using features, formed using the discrete wavelet transform (DWT), from the ECG and acceleration signals provided the highest classification accuracy, with an F1 score of 0.914. However, the novel employment of just the accelerometer signal during classification provided a comparable F1 score of 0.879. By employing one or a combination of the analysed sensors a preliminary test for sleep apnea, prior to the requirement for gold standard testing, can be performed.

Rotationally controlled centrifugo-pneumatic valving utilizing dissolvable films

Here we report on a novel, centrifugo-pneumatic valving scheme based on water-dissolvable films. Compared to previous active valving approaches, this valving technique is merely controlled by introducing aqueous solutions to the substrate and allowing for dissolution; therefore lending itself to simple fabrication in microfluidic devices. Furthermore, the ability to tailor films over a range of dissolution times introduces novel capabilities for valving on the centrifugal platform allowing for greater diffusion barriers to liquids even at high burst frequencies. This report outlines the underlying working principle, assembly, and characterization of the novel valving scheme utilizing the dissolvable films.

Graphene Oxide membranes for phase-selective microfluidic flow control

This paper investigates the unique properties of multilayer Graphene Oxide (GO) as a barrier selective to solvents, as well as the state of aggregation of fluids. To this end, we developed novel processes for the assembly of GO as membranes into polymeric microfluidic systems. We demonstrate that GO blocks pressurized air and organic solutions while it is permeable to water. It is planned to employ these GO membranes as a flow control element in a microfluidic system.

Centrifugally automated solid-phase purification of RNA

The purity and integrity of RNA after extraction from a biosample like blood are critical for both downstream analysis and development of on-chip diagnostics. We report for the first time on a fully centrifugally automated solidphase purification of RNA on an integrated microfluidic disc with sequential release of on-board reagents. Building on our earlier work the system successfully concatenates event-triggered valving and centrifugally controlled routing in order to collect purified RNA separately from the aqueous and organic wastes. In this article two-stage purification of RNA and sample conditioning through novel high-frequency release and hybrid event-triggered release valves is demonstrated.

Graphene-oxide enabled centrifugo-pneumatic routing of flows

We show a novel, centrifugo-pneumatic scheme for solvent-selective routing of organic and aqueous flows based on an integrated, graphene oxide (GO) membrane. We then implement a sequential, multi-reagent protocol geared towards automated solid-phase extraction of nucleic acids with a sequence of washing and elution steps with aqueous and organic liquids.