Fig. 4

Confocal Laser Scanning Microscopy (CLSM) images acquired at different times on PEMA-DEC gels applied on the top surface of Ordinary, Brown, and Insulating PSTs (i.e. respectively OT, BT, and IT). The DEC solvent is labeled green with Cou6, while the adhesive layers are labeled red with RhBITC. The PSTs backings are not labeled, and thus appear black. Because light is sent on the system from below, the DEC-loaded gel is visible only in the case of OT, where the PST is transparent and light passes through the backing, up to the gel. In the other cases, light stops at the backing and cannot reach the gel, which appears as black. At time t = 0 the adhesive layer is well defined and not affected by DEC; after penetration of the solvent through the backing (t = 15–20 min) the adhesive layers become swollen with DEC, as also highlighted by the change in color from red to yellow-green