A novel microchip based on indium tin oxide coated glass for contactless conductivity detection

Microfluidic Device Integrated With PDMS Microchannel and Unmodified ITO Glass Electrodes for Highly Sensitive, Specific, and Point-of-Care Detection of Copper and Mercury

This work delves upon developing a two-layer plasma-bonded microfluidic device with a microchannel layer and electrodes for electroanalytical detection of heavy metal ions. The three-electrode system was realized on an ITO-glass slide by suitably etching the ITO layer with the help of CO2 laser. The microchannel layer was fabricated using a PDMS soft-lithography method wherein the mold created by maskless lithography. The optimized dimensions opted to develop a microfluidic device with length of 20 mm, width of 0.5 mm and gap of 1 mm. The device, with bare unmodified ITO electrodes, was tested to detect Cu and Hg by a portable potentiostat connected with a smartphone. The analytes were introduced in the microfluidic device with a peristaltic pump at an optimal flow rate of [Formula: see text]/min. The device exhibited sensitive electro-catalytic sensing of both the metals by achieving an oxidation peak at -0.4 V and 0.1 V for Cu and Hg respectively. Furthermore, square wave voltammetry (SWV) approach was used to analyze the scan rate effect and concentration effect. The device also used to simultaneously detect both the analytes. During simultaneous sensing of Hg and Cu, the linear range was observed between [Formula: see text] to [Formula: see text], the limit of detection (LOD) was found to be [Formula: see text] and [Formula: see text] for Cu and Hg respectively. Further, no interference with other co-existing metal ions was found manifesting the specificity of the device to Cu and Hg. Finally, the device was successfully tested with real samples like tap water, lake water, and serum with remarkable recovery percentages. Such portable devices pave way for detecting various heavy metal ions in a point-of-care environment. The developed device can also be used for detection of other heavy metals like cadmium, lead, zinc etc., by modifying the working electrode with the various nanocomposites.

A plug-in electrophoresis microchip with PCB electrodes for contactless conductivity detection

A plug-in electrophoresis microchip for large-scale use aimed at improving maintainability with low fabrication and maintenance costs is proposed in this paper. The plug-in microchip improves the maintainability of a device because the damaged microchannel layer can be changed without needing to cut off the circuit wires in the detection component. Obviously, the plug-in structure reduces waste compared with earlier microchips; at present the whole microchip has to be discarded, including the electrode layer and the microchannel layer. The fabrication cost was reduced as far as possible by adopting a steel template and printed circuit board electrodes that avoided the complex photolithography, metal deposition and sputtering processes. The detection performance of our microchip was assessed by electrophoresis experiments. The results showed an acceptable gradient and stable detection performance. The effect of the installation shift between the microchannel layer and the electrode layer brought about by the plug-in structure was also evaluated. The results indicated that, as long as the shift was controlled within a reasonable scope, its effect on the detection performance was acceptable. The plug-in microchip described in this paper represents a new train of thought for the large-scale use and design of portable instruments with electrophoresis microchips in the future.

Microfluidic contactless conductivity cytometer for electrical cell sensing and counting

An integrated and cost-effective microfluidic contactless conductivity cytometer for cell sensing and counting.

Microfluidic platform integrated with worm-counting setup for assessing manganese toxicity

We reported a new microfluidic system integrated with worm responders for evaluating the environmental manganese toxicity. The micro device consists of worm loading units, worm observing chambers, and a radial concentration gradient generator (CGG). Eight T-shape worm loading units of the micro device were used to load the exact number of worms into the corresponding eight chambers with the assistance of worm responders and doorsills. The worm responder, as a key component, was employed for performing automated worm-counting assay through electric impedance sensing. This label-free and non-invasive worm-counting technique was applied to the microsystem for the first time. In addition, the disk-shaped CGG can generate a range of stepwise concentrations of the appointed chemical automatically and simultaneously. Due to the scalable architecture of radial CGG, it has the potential to increase the throughput of the assay. Dopaminergic (DAergic) neurotoxicity of manganese on C. elegans was quantitatively assessed via the observation of green fluorescence protein-tagged DAergic neurons of the strain BZ555 on-chip. In addition, oxidative stress triggered by manganese was evaluated by the quantitative fluorescence intensity of the strain CL2166. By scoring the survival ratio and stroke frequency of worms, we characterized the dose- and time-dependent mobility defects of the manganese-exposed worms. Furthermore, we applied the microsystem to investigate the effect of natural antioxidants to protect manganese-induced toxicity.

Electrochemical methods in conjunction with capillary and microchip electrophoresis

Electromigrative techniques such as capillary and microchip electrophoresis (CE and MCE) are inherently associated with various electrochemical phenomena. The electrolytic processes occurring in the buffer reservoirs have to be considered for a proper design of miniaturized electrophoretic systems and a suitable selection of buffer composition. In addition, the control of the electroosmotic flow plays a crucial role for the optimization of CE/MCE separations. Electroanalytical methods have significant importance in the field of detection in conjunction with CE/MCE. At present, amperometric detection and contactless conductivity detection are the predominating electrochemical detection methods for CE/MCE. This paper reviews the most recent trends in the field of electrochemical detection coupled to CE/MCE. The emphasis is on methodical developments and new applications that have been published over the past five years. A rather new way for the implementation of electrochemical methods into CE systems is the concept of electrochemically assisted injection which involves the electrochemical conversions of analytes during the injection step. This approach is particularly attractive in hyphenation to mass spectrometry (MS) as it widens the range of CE-MS applications. An overview of recent developments of electrochemically assisted injection coupled to CE is presented.

Recent advances in applications of capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C⁴D): an update

Capillary electrophoresis with a capacitively contactless conductivity detector (CE-C⁴D) is becoming a significant useful technique for the analysis of analytes in various fields such as pharmaceutical, biomedical, food and environmental. This review is an update describing the recent developments in the application of CE with a C⁴D detector.