In general, chitosan should be dissolved in strong acidic media (such as acetic acid) before it could be applied as

hydrogels. However, it was found that chitosan could also be dissolved in the ferric solution to form ferricchitosan

complex via coordination interaction. Subsequently, the ferric-chitosan complex was successfully introduced

into the hydrogel system to obtain tough, adhesive and conductive chitosan-polyacrylamide double

network (CS-PAAm DN) hydrogels. Surprisingly, CS-PAAm DN hydrogel could repeatedly adhere to various solid

materials and biological tissues through physical interactions. The maximum peeling force was 256 N/m on the

aluminum surface. Moreover, the hydrogel exhibited adequate mechanical performance (135 kPa, 2332%). And

the introduction of ferric chloride could also endow the hydrogel with conductive performance. As a result, the

strategy based on tough, adhesive and conductive polysaccharide hydrogels mediated by ferric solution would

broaden the path to fabricate a new generation of soft materials for wide applications.