Monitoring FET flow control and wall adsorption of charged fluorescent dye molecules in nanochannels integrated into a multiple internal reflection infrared waveguide
Abstract
Using Si as the substrate, we have fabricated multiple internal reflection infrared waveguides embedded with a parallel array of nanofluidic channels. The channel width is maintained substantially below the mid-infrared wavelength to minimize infrared scattering from the channel structure and to ensure total internal reflection at the channel bottom. A Pyrex slide is anodically bonded to the top of the waveguide to seal the nanochannels, while simultaneously enabling optical access in the visible range from the top. The Si channel bottom and sidewalls are thermally oxidized to provide an electrically insulating barrier, and the Si substrate surrounding the insulating SiO2 layer is selectively doped to function as a gate. For fluidic field effect transistor (FET) control, a DC potential is applied to the gate to manipulate the surface charge on SiO2channel bottom and sidewalls and therefore their ζ-potential. Depending on the polarity and magnitude, the gate potential can accelerate, decelerate, or reverse the flow. Here, we demonstrate that this nanofluidic infrared waveguide can be used to monitor the FET flow control of charged,