A microfluidic chip for terahertz spectral detection

Fluidic chips as sample storage devices have been widely used to control and analyze traces of solutions by terahertz time domain spectroscopy (THz-TDS). This paper presents a fluidic chip fabricated with ultra-thick micro-fluidic structures utilizing SU-8 photoresist for THz spectral detection. The chip consists of 2 pieces of quartz windows and a photoresist structure serves as liquid cell between the windows. In order to reduce the attenuation of THz energy by the windows and guarantee measurement stability, an infrared quartz with thickness of 1mm is adopted as the windows. For the purpose of improving the signal-to-noise ratio (SNR) in the frequency band between 1.0 THz-1.5 THz, and making the liquid film thickness match the THz optical path, the structure depth is designed to be 50μm. Water absorption coefficient at 0.1THz-1.5THz was detected with this chip. The result indicates that the chip has a good stability for terahertz spectral detection.