Sensitive Gas Analysis System on a Microchip and Application for On-Site Monitoring of NH₃ in a Clean Room

Abstract

A portable, highly sensitive, and continuous ammonia gas monitoring system was developed with a microfluidic chip. The system consists of a main unit, a gas pumping unit, and a computer which serves as an operation console. The size of the system is 45 cm width × 30 cm depth × 30 cm height, and the portable system was realized. A highly efficient and stable extraction method was developed by utilizing an annular gas/liquid laminar flow. In addition, a stable gas/liquid separation method with a PTFE membrane was developed by arranging a fluidic network in three dimensions to achieve almost zero dead volume at the gas/liquid extraction part. The extraction rate was almost 100% with a liquid flow rate of 3.5 μL/min and a gas flow rate of 100 mL/min (contact time of ~15 ms), and the concentration factor was 200 times by calculating the NH(3) concentration (w/w unit) in the gas and liquid phases. Stable phase separation and detection was sustained for more than 3 weeks in an automated operation, which was sufficient for the monitoring application. The lower limit of detection calculated based on a signal-to-noise ratio of 3 was 84 ppt, which showed good detectability for NH(3) analysis. We believe that our system is a very powerful tool for gas analysis due to the advantages of portable size, high sensitivity, and continuous monitoring, and it is particularly useful in the semiconductor field.

A Peristaltic Pump Integrated on a 100% Glass Microchip Using Computer Controlled Piezoelectric Actuators

“…A number of applications such as optical detection, organic synthesis [17] gas analysis systems [18], adhesive cell patterning and culturing [19], biomolecule separations [20][21][22], and biological analysis systems [23] have been developed which were difficult to realize using traditional polymer microchips. However, glass is very rigid.…”

Micro Total Analysis Systems for Cell Biology and Biochemical Assays

“…(c) DNA was extracted from buccal swabs and amplified by PCR in the polycarbonate (PC) cartridge, then transferred to the glass chip for separation and detection. Figures reproduced with permission from references 125, 129 and 143.…”

Micro Total Analysis Systems: Fundamental Advances and Applications in the Laboratory, Clinic, and Field

“…241 Another device utilized a 3D gas/liquid laminar flow to extract and concentrate ammonia from air and operated continuously for three weeks in a cleanroom at nearly 100% extraction efficiency. 242 Another on-chip system distilled gaseous sulfur dioxide (SO 2 ) from wine; this device will allow wine producers to measure SO 2 on site, rather than shipping samples to laboratories (Figure 9b). 243 Other devices accepted real-world samples with minimal processing, such as a device to measure methanol content in red wine with an integrated microreactor and detection channels designed to fit into a standard UV spectrophotometer.…”