Fig. 3
From: Self-folding of thick paper via continuous solution supply analyzed by FTIR spectroscopy
Cross-sectional snapshots of the through-thickness concentration \(\:C(z,\:t)\) from one-dimensional diffusion simulations. The colour map ranges from high concentration (\(\:C=1\)) to low concentration (\(\:C=0\)). (a) Inkjet method: immediately after printing, a transition to the Free Reaction Phase occurs (\(\:0\:\text{s}\le\:t\le\:400\:\text{s}\)). The penetration remains confined near the surface; the concentration gradient relaxes over time due to diffusion into the interior, and a wide high-concentration region across the thickness does not develop. (b) Filter-paper method: Loading Penetration Phase (\(\:-300\:\text{s}\le\:t<0\:\text{s}\)) followed by Free Reaction Phase (\(\:0\:\text{s}\le\:t\le\:400\:\text{s}\)). At \(\:t=0\:\text{s}\), a wide high-concentration region across the thickness has already formed, and the highly imbibed state is maintained for an extended period.
