Fig. 4: Prevention of vapour condensation on the viewing window using superhydrophobic and superhydrophilic materials.
a, Cross-sectional view of the LFA showing the mechanism of sweat vapour condensation on the surface of a superhydrophobic or hydrophobic viewing window. b, Cross-sectional view of the LFA showing a failure mechanism due to sweat flow through a viewing window entirely comprising a superhydrophilic window. c, Cross-sectional view of the LFA assembly with a combination of superhydrophobic and superhydrophilic materials comprising the viewing window. The result prevents vapour condensation above the test line and below the control line and blocks sweat flow through the window. d, Optical image of a skin-interfaced device that uses iontophoretic stimulation of sweat to illustrate the effect of various material types on vapour condensation. e,f, Photograph of an LFA device that uses a superhydrophobic and superhydrophilic viewing window at 15 min (e) and 4 h (f). g, Transmittance change as a function of time for normal PET, superhydrophilic PET and a superhydrophobic viewing window (PET + PSA) at 30 °C in the presence of water. The data represent mean values ± s.d. (n = 3 technical replicates). h, Transmittance spectra of glass, normal PET, superhydrophilic PET and superhydrophobic PET + PSA at the initial state. n = 1. i, Transmittance spectra of glass, normal PET, superhydrophilic PET and superhydrophobic PET + PSA after 6 h of heating at 30 °C in the presence of water. n = 1. CA, contact angle.
