Silica nanochannel device for pH sensing based on surface charge density changes

This paper demonstrates a novel micro/nano fluidic device for continuous pH sensing of small fluid volumes. The working principle of the device is based on the change of the surface charge density within the silica nanochannels with respect to the pH levels of the electrolyte. In order to measure pH levels of various solutions, AC potential is applied along the silica nanochannels which have 50 nm depth, 2 µm width, and 30 µm length. The running current along the nanofluidic channels is directly measured with respect to pH levels. It was found that the running current is inversely proportional to pH levels regardless of ion concentrations.