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Miniaturisation of microchip capillary electrophoresis (MCE) is becoming an increasingly important research topic, particularly in areas related to micro total analysis systems or lab on a chip. One of the important features associated with the miniaturised MCE system is the portable power supply unit. In this work, a very low electric field MCE utilising an amperometric detection scheme was designed for use in DNA separation. The device was fabricated from a glass/polydimethylsiloxane hybrid engraved microchannel with platinum electrodes sputtered onto a glass substrate. Measurement was based on a three-electrode arrangement, and separation was achieved using a very low electric field of 12 V/cm and sample volume of 1.5 µl. The device was tested using two commercial DNA markers of different base pair sizes. The results are in agreement with conventional electrophoresis, but with improved resolution. The sensitivity consistently higher than 100 nA, and the separation time approximately 45 min, making this microchip an ideal tool for DNA analysis.

Electrochemical detection (ECD) is one of the best means for producing DNA biosensors and disposable microchips, oriented for electroactive analyte's separation and detection applications like biomedical and in vitro diagnostic. Electrode material is one of the major factors that influence the performance and development of biosensors and ECD microchips. Traditionally, the ECD sensing has been based on platinum electrode which is costly though it offers good current sensitivity. In this study a copper electrode has been investigated as an alternative sensing strategy. Preliminary results indicate that the copper electrodes are also capable of performing both detection and separation, yielding a significant limit of detection. On average the copper electrodes are capable of detecting the redox currents which are consistently higher 10 IlA compared to 30 IlA for platinum electrodes using DNAanalytes. This work will pave the way in designing a more affordable and disposable microchips.

A leakage-free and disposable biochip for deoxyribonucleic acid (DNA) separation and detection is developed in this study. The biochip comprises of 50 mm long polydimethylsiloxane (PDMS) microchannel and copper electrodes engraved on flame retardant (FR-4) printed circuit board (PCB) substrate. An inhibitor made from photocurable diacrylate bisphenol-A polymer (DABA) was used to establish a permanent bonding between PDMS and PCB substrates. Pull-off test experiments resulted in average strength of 287.4 kPa and a standard deviation of ± 23.8 kPa. These results are comparable to recent studies on leak-free microfluidic applications. Meanwhile, the leakage test showed that the biochip could withstand a pressure of more than 190 kPa, which is sufficiently high for most DNA measurements. Finally, experiments performed on two different DNA samples indicated that the proposed design could accurately detect DNA fragments with current sensitivity higher than 100 nA, under electric field strength of 20 V/cm. The new design effectively seals the biochip, thus preventing leakage of liquid from the sensor matrix. Together with its biologically and electrochemically inert characteristic, it opens up possibilities in building a truly portable biosensing device.