Solid-state nanopores have emerged as possible candidates for next-generation DNA sequencing devices. In this talk, we will review our recent work in development of solid-state nanopore channels that are selective towards single strand DNA (ssDNA). Nanopores functionalized with a 'probe' of hair-pin loop DNA can, under an applied electrical field, selectively transport short lengths of 'target' ssDNA that are complementary to the probe. Even a single base mismatch between the probe and the target results in longer translocation pulses and a significantly reduced number of translocation events. Our single molecule measurements allow us to separately measure the molecular flux and the pulse duration, providing a tool to gain fundamental insight into the channel-molecule interactions. The results can be explained in the conceptual framework of diffusive molecular transport with particle-channel interactions.