Measurements of pH in Fluidic Chip by Terahertz Chemical Microscope

摘要

Micro-total analysis systems (μTAS) have been attracted by many researchers because it can deal with chemical reactions with small amounts of chemicals. Because the properties of solutions are dominated by flow resistances and channel structures, direct monitoring of the chemical concentration is required to develop the μTAS. Recently, A Terahertz (THz) Chemical Microscope (TCM) has been proposed and developed to visualize the chemical concentration in fluidic chips. The fluidic chip with a "sensing plate" as the bottom wall of the channel was fabricated. The sensing plate consists of Insulator/Semiconductor/Substrate, and the insulator side of pate was contacted to the chemical solution flowing in the channel. When an ultra-short laser pulse hits the semiconductor layer, THz waves are generated and radiated to free space through the substrate. The amplitude of THz waves can be related to the depletion layer of the semiconductor layer. Therefore, when protons in the channel are adsorbed to the plate and changes the surface potential of the plate, the amplitude of THz was also changes. Thus the distribution of proton concentration in the flow channel can be obtained by scanning the laser. Here, we optimize the optical systems to improve the spatial resolution of TCM, and demonstrated to monitor the TCM image of 1-mmm-width fluidic channels.