Single molecule ionic current sensing in segmented flow microfluidics.

Herein, we describe the integration of two glass nanopores into a segmented flow microfluidic device with a view on enhancing the functionality of label free, single molecule nanopore sensors. Within a robust and mechanically stable platform, individual droplet compositions are distinguished before single molecule translocations from the droplet are detected electrochemically via the Coulter principle. This result is highly significant, combining the sensitivity of single molecule methods and their ability to overcome the clouding of the ensemble average with the "isolated microreactor" benefits of droplet microfluidics. Furthermore, devices as presented here provide the platform for the development of systems where the injection and extraction of single molecules allow droplet composition to be controlled at the molecular level.

Label-free in-flow detection of single DNA molecules using glass nanopipettes.

With the view of enhancing the functionality of label-free single molecule nanopore-based detection, we have designed and developed a highly robust, mechanically stable, integrated nanopipette-microfluidic device which combines the recognized advantages of microfluidic systems and the unique properties/advantages of nanopipettes. Unlike more typical planar solid-state nanopores, which have inherent geometrical constraints, nanopipettes can be easily positioned at any point within a microfluidic channel. This is highly advantageous, especially when taking into account fluid flow properties. We show that we are able to detect and discriminate between DNA molecules of varying lengths when motivated through a microfluidic channel, upon the application of appropriate voltage bias across the nanopipette. The effects of applied voltage and volumetric flow rates have been studied to ascertain translocation event frequency and capture rate. Additionally, by exploiting the advantages associated with microfluidic systems (such as flow control and concomitant control over analyte concentration/presence), we show that the technology offers a new opportunity for single molecule detection and recognition in microfluidic devices.