High performance nanostructured black silicon biosensors

Nanomaterial-based biosensors are an emerging approach to measuring chemicals that bind to biological receptors. The current status-quo technologies are focused on horizontal, field-effect transistor-based devices. We have developed a novel vertically oriented silicon (Si) nanowire (NW) array, formed using metal-assisted chemical etching (MACE), as the basis for a low-cost, highly sensitive biosensor capable of estrogen detection. A Si NW solar cell acts as the transducing element in the biosensor device. To assemble an optimal performing biosensor, the fabrication steps were continuously refined, and new techniques were utilized.

The Si NW biosensor was developed to detect estrogenic compounds in waterways. Estrogens and estrogen-mimicking compounds in the environment are known to cause negative impacts to ecosystems and have adverse effects on human health. The biosensor was functionalized by attaching estrogen receptor alpha (ER-α) to the Si NW surface. Fluorescence measurements helped quantify the distribution of ER-α across the surface and demonstrated the benefits of a nanotextured Si surface compared to a planar one. Selectivity of the biosensor was established by testing the biosensor with non-estrogen compounds. We also effectively proved that molecular binding was occurring only between the estrogen and its receptor. A higher current density change was observed in the biosensor when exposed to higher concentrations of estrogens. An optimized doping level that resulted in sheet resistivity values between 1000 and 1200 Ω/sq was determined to generate the highest sensitivity biosensor response. A vertically oriented Si NW array-based biosensor was developed as a possible field deployable device for cheap and sensitive real-time measurements.