Fig. 1.

Design and adhesion process of the SLU-adhesive. (A) A Sudan IV-stained adhesive droplet (7 μL) spontaneously wets PMMA substrate surface, forming a complete spreading adhesive layer. (B) The theoretical study and schematic diagram of the self-strengthening mechanism of water-induced adhesive in the spreading process. Scanning electron microscope (SEM) shows a sandcastle worm-like protein pore structure inside SLU-adhesive. (C and D) Digital images show the adhesion of SLU-adhesive to the organic (PMMA) and inorganic (Fe) surfaces under water. After being placed in water (20 °C, no applied pressure) for 1 h, the adhesion to different substrates withstood water blasting (2 bar, 45 s). (E) Adhesive polymer blend with embedded cotton thread casted onto an Fe sheet in water. After 1 h, adhesion force can support the weight (100 g) of the sheet in air.