We report on the implementation of a microstructure comprising an array of micropillars to create a thin and stable film of nematic liquid crystal (LC), 5CB: 4'-pentyl-4-cyanobiphenyl, and the use of the microsystem for the colorimetric detection of vapor analytes. The microstructure uses capillary force generated by an array of cylindrical micropillars to steadily support a 22 µm thin film of LC, and overcomes susceptibility to gravity and shock. The feasibility of using the microsystem for gas phase detection is demonstrated by using dimethyl methylphosphonate (DMMP) gas to change the orientation of the LC and hence modulate the intensity of light transmitted through a crossed pair of polarizing films. The microstructure potentially offers a simple and portable solution to toxic gas detection.