A Microfabricated Propofol Trap for Breath-Based Anesthesia Depth Monitoring

This paper reports a golden microtrap chip for anesthetic depth monitoring. The chip selectively captures the propofol (2,6-diisopropylphenol) compound, which is a widely used substance for anesthesia, by filtering out the other species found in human breath. The fabricated silicon-glass chip is 12 mm on each side and consists of an array of high aspect ratio parabolic reflectors inside its 7 mm × 7 mm × 0.24 mm cavity. The interior surfaces of the chip are coated with an electroplated gold layer having a surface roughness of around 6.82 nm, which is an order of magnitude higher than a gold layer deposited by electron (e)-beam evaporation. Uncoated and e-beam gold-coated chips are unable to trap propofol and other compounds found in human breath. In contrast, silicon-glass chips coated with Tenax TA (2,6 diphenylene oxide), a gas adsorbing polymer, captures propofol among other volatiles present in human breath. Only devices coated with an electroplated gold layer demonstrate selective affinity for the target compound propofol. For the same propofol concentration, these golden microtraps show consistent capture efficiency with less than 8% variation in the trapped propofol amount while tested with different human breath samples. These microfabricated chips have the potential to accurately quantify the amount of propofol present in human breath samples without incorporating the gas chromatography column into the testing setup, resulting in faster analysis and reduced cost and complexity.