This thesis describes a new approach to the investigation of the contents of microfluidic droplets at the single molecule level. Glass nanopores with diameters below 25nm, formed by pipette pulling, are inserted into a microfluidic channel with a height and width of 100 μm. Subsequently, a segmented flow of buffered KCl droplets in an FC-40 carrier oil is flowed through the device and analysed via changes in the measured electrical signal upon application of a voltage between the nanopipettes.
Initially, the thesis focuses on the optimisation of droplet generation and pipette performance. A T-junction geometry and a novel method of droplet generation using an integrated pipette are both trialled as methods for droplet production in the device. In addition, atomic layer deposition (ALD) is investigated as an approach to optimise the size of the glass nanopore for the detection of single molecules.
Subsequently, droplets in the segmented flow are examined with the device. Optical studies are undertaken to study the viability of droplets in the device and the preservation of their ‘isolated microreactor’ status. The length and frequency of droplets is then measured electrically and compared to an optical control, the excellent agreement between the two methods confirming the validity of the electrical approach. Attention then turns to the measurement of the bulk properties of the droplet with the determination of the KCl concentration within individual droplets. Finally, single molecules of 10 kbp double stranded DNA are translocated from within the droplet into the nanopipette, illustrating the device’s potential for the analysis of droplet contents and the control of their contents at the single molecule level.