Ionic conductive and stretchable interpenetrating hydrogels prepared with homogenously synthesized acrylamide-modified agar and polyacrylamide for strain sensing

In this article, the IPN hydrogels were prepared with acrylamide-modified agar (AMA), oxidized alginate (ADA) and polyacrylamide (PAM). The agar was firstly homogenously modified with acrylamide to facilitate the formation of hydrogen bonds and enhancement of the ionic conductivity of the hydrogel. The prepared IPN hydrogels showed high flexibility and conductivity. The composite hydrogel prepared with 20 wt% acrylamide, 0.25 wt% AMA and 5% ADA (hydrogel-5) possessed high toughness and can be stretched 20 times of its origin length. The hydrogel-5 also showed highest elastic modulus of 110 kPa compared with other hydrogels. The free potassium and sodium ions in acrylamide-modified agar and oxidized alginate chains endowed the hydrogel with conductive properties. The IPN hydrogels showed strain sensitive properties and can be used to detect various motion of human beings. The hydrogel still possessed high flexibility and conductivity after storing for six months. The IPN hydrogels with conductivity and high mechanical properties can be applied in various engineering fields.