Biomolecule size-dependent sensitivity of porous silicon sensors

Nanoporous materials hold great potential for improving the performance of biosensors due to their large available surface area and their capability for size-selective infiltration. One of the principal challenges associated with the use of nanopores is achieving efficient infiltration of molecules whose size is of the same order of magnitude as the pore radius. There is an intrinsic trade-off between ease of infiltration and level of sensor response for the detection of biomolecules in nanopores. DNA molecules of lengths between approximately 1.5 nm and 5.5 nm have been exposed to porous silicon waveguide sensors with nanopore diameters of approximately 30 nm in order to experimentally determine the size-dependent sensitivity. While theoretical calculations that do not take into account the infiltration challenges of biomolecules in nanopores suggest that longer DNA molecules yield a stronger sensor response, experimental results show that shorter molecules produce a larger response due to their ease of infiltration.