A high-field asymmetric ion mobility spectrometry (FAIMS) chip based on printed circuit board (PCB) brazing has been fabricated. A needle-to-ring structure was used as the ion source. The ring electrode was formed by punching a 3 mm hole on the PCB and covering it with copper. The FAIMS chip was composed of two PCB boards connected by brazing. The peak value of a FAIMS spectrum was increased by reducing the ballast resistance and increasing the discharge voltage and gas velocity. When ethanol was used as the analyte, the limit of detection (LOD) is approximately 0.06 mg/L.

As an essential indicator of liver function, bilirubin is of great significance for clinical diagnosis. A non-enzymatic sensor has been established for sensitive bilirubin detection based on the bilirubin oxidation catalyzed by unlabeled gold nanocages (GNCs). GNCs with dual-localized surface plasmon resonance (LSPR) peaks were prepared by a one-pot method. One peak around 500 nm was ascribed to gold nanoparticles (AuNPs), and the other located in the near-infrared region was the typical peak of GNCs. The catalytic oxidation of bilirubin by GNCs was accompanied by the disruption of cage structure, releasing free AuNPs from the nanocage. This transformation changed the dual peak intensities in opposite trend, and made it possible to realize the colorimetric sensing of bilirubin in a ratiometric mode. The absorbance ratios showed good linearity to bilirubin concentrations in the range of 0.20~3.60 μmol/L with a detection limit of 39.35 nM (3σ, n = 3). The sensor exhibited excellent selectivity for bilirubin over other coexisting substances. Bilirubin in real human serum samples was detected with recoveries ranging from 94.5 to 102.6%. The method for bilirubin assay is simple, sensitive and without complex biolabeling.