Fig. 3

Toughening the silane modified PAAm-PDMS by infusing a dissipative interpenetrating network. a A silane-modified PDMS precursor is spin-coated on a glass slide. A silane-modified PAAm hydrogel is bonded on the silane-modified PDMS. b The bilayer is immersed in the precursor of the PAAm-co-PAAc hydrogel for 1 day. c The precursor polymerizes under UV lamp, but does not crosslink at this stage. d The sample is immersed in FeCl₃ solution for 1 day. The Fe³⁺ ions form coordinate compounds with the carboxylic acid groups, which physically crosslinks the PAAm-co-PAAc network. The siloxane bonds between the PAAm and PDMS chains are strong bonds, and the coordination complexes are weak bonds. The hydrogel becomes brownish after the crosslinking. e The sample is then immersed in distilled water for 1 day to remove excess Fe³⁺ ions