Steps towards spatially resolved single molecule detection in solution

Spatially resolved single molecule detection in solution is a prerequisite for molecule tracking and provides new opportunities in single molecule manipulation, for example in a sample flow. A detector with fast timing properties and high spatial resolution is required for these purposes. We introduce a concept for spatially resolved optical single molecule detection in an epi-illuminated microscope using a novel kind of detector and a new algorithm in configurable hardware for intelligent data processing. The analysis is performed on a parallel hardware interface and includes burst detection. It can be extended to on-line spatial and temporal data analysis. This detector will be used in combination with a molecular sorter where molecules are sorted in a microstructured flow device made of silicon. In a first step towards such sorting in these microstructures, we show that a reliable detection of single molecules in silicon microstructures is possible in zero-dimensional detection volumes. The noise structure of the data is analysed in terms of Poissonian statistics and it is shown that in the smallest structure used (depth 20 μm) a signal-to-noise ratio of 40 is achieved.