Detection of short ssDNA and dsDNA by current-voltage measurements using conical nanopores coated with Al2O3 by atomic layer deposition

DNA detection using solid state nanopores is limited by the difficulty of the detection of short DNA strands due to their very short dwell time. Here, we report on the fabrication of nanopores using a track-etching technique along with the atomic layer deposition of aluminum oxide. This method allows shaping of conical nanopores, controlling their diameter, and passivation of the surface by Al2O3. Through the optimized nanopore, short DNA (10 nM) having 10 and 40 nucleotides in length were detected both at the single stranded and double stranded levels. The analysis of current trace shows signal to noise ratio of 2 and 4 for ssDNA and dsDNA respectively and a dwell time at ms scale. This is possible because of both the high aspect ratio and the Al2O3 coating that permit to decrease the DNA velocity.