Flow-insensitive micro-thermal conductivity detector with semi-diffusion gas channel

A novel micro-thermal conductivity detector with a semi-diffusion gas channel is demonstrated. This semi-diffusion channel can reduce the flow-rate interference significantly by lowering the gas flow velocity above the hot film and maintains fast response speed at the same time. Simulations indicate that the semi-diffusion type with triangular shape has the best flow-insensitive effect. When the temperature of the hot film is about 500 K, the maximal temperature deviation of the hot film caused by flow rate change in this case can be decreased by 82.4% compared with the traditional straight type. Experiments are carried under the conditions of sample and carrier gas commonly used in gas chromatograph (GC), which is achieved by using He and CO2. With the sample gas flow ranging from 1 to 20 sccm, the voltage deviation in the semi-diffusion type is reduced for as much as 85.1% of that in the straight type. This effect is also verified in binary gases with various thermal conductivities. In addition, the recovery time of the semi-diffusion design is almost the same as the straight type, less than 170 ms, indicating it is suitable for the rapid gas detection in GC.