An improved Nicholson–Ross–Weir method for thin material characterization using adsorption spreading under negative pressure

This paper presents an improved Nicholson–Ross–Weir method based on negative pressure adsorption for characterizing the electromagnetic properties of flexible or extremely thin materials. A stable pressure difference is established during measurements, and an air-permeable support block is employed to suppress sample deformation. Furthermore, the anisotropy of the support block is incorporated into the theoretical derivation. The effectiveness of the proposed method is validated through experimental measurements of several thin materials with thicknesses of 158, 545, and 60 μm in the C-band.