Nanowire pH Sensor for Biological Applications
A cell’s internal and external pH plays a critical role in influencing many cellular chemical reactions and functions. Yet measuring pH without the appearance of artifacts in these challenging cellular and extracellular nanoscale environments is very difficult. New silicon nanowire (SiNW) pH sensors that possess long-term stability in these difficult environments have been developed by scientists at Lawrence Berkeley National Laboratory and their collaborators. The sensors were produced using a top-down fabrication process combining electron beam lithography (EBL) with conventional photolithography. A passivation layer (silicon nitride applied using plasma enhanced chemical vapor deposition) is coated on the SiNW’s surface to enhance electrical insulation and ion-blocking properties. This study shows that the application of these techniques results in improved stability of the sensor and enhances its performance. The paper explains how to achieve reliable performance in biological systems and discusses the trade-off between stability and pH sensitivity of the sensor response.
Choi, S., I. Park, Z. Hao, H.-Y. Holman, and A. P. Pisano. 2012. “Quantitative Studies of Long-Term Stable, Top-Down Fabricated Silicon Nanowire pH Sensors,” Applied Physics A: Materials Science & Processing, DOI: 10.1007/s00339-011-6754-9.