Perforated films used as test specimens for compensation of asymmetry in electron microscope lenses can be made by introducing water or glycerol into a Formvar solution. This can be done by preparing an emulsion or by exposing a thin layer of Formvar solution on the surface of glass to steam or moist air. Consistent production of small, round test holes with smooth edges is difficult. The following method employs solvent treatment for enlarging perforations formed in high humidity. Edge characteristics and hole size can be controlled easily and consistently. Useful holes as small as 0.15μ diameter can be produced.Procedures described by Bradley are used to clean glass slides, dissolve Formvar in ethylene dichloride, cast films on glass, and mount films on grids. In a room or chamber at room temperature (23 C) with 50-70%. relative humidity, the clean glass slides are dipped into a Coplin staining jar containing 0.2-0.4% (w/v) Formvar solution. Figure 1 shows perforations formed during casting in a chamber at 60% relative humidity using a 0.4% Formvar solution. The perforated films are mounted on grids, which are immersed in acetone, absolute methanol, or chloroform-absolute methanol (1:9) contained in compartments of a depression plate.
Enhanced Capacitive Humidity Sensing Performance at Room Temperature via Hydrogen Bonding of Cyanopyridone-Based Oligothiophene Donor
