Label-free porous silicon membrane waveguide for DNA sensing

We report a label-free porous silicon membrane waveguide biosensor based on a 1 mu m thick freestanding porous silicon film with 100 nm diameter pores. The sensor operates in the Kretschmann configuration. A formvar polymer film provides robust adhesion of the porous silicon membrane to a rutile prism and enables confinement of guided modes in the porous silicon membrane. Attenuated total reflectance measurements are performed, along with theoretical calculations, to fully characterize the waveguide. The sensitivity of the sensor is investigated through DNA hybridization in the porous silicon membrane. A detection limit of 42 nM was demonstrated for 24-base pair DNA oligonucleotides. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3005620]