An Antibacterial, Highly Sensitive Strain Sensor Based on an Anionic Copolymer Interpenetrating with κ‑Carrageenan

Polysaccharide-based hydrogels are suitable for use in
the field
of flexible bioelectronics due to their benign mechanical properties
and biocompatibility. However, the preparation of hydrogel sensors
with high performance without affecting their physicochemical properties
(e.g., flexibility, toughness, self-healing, and antibacterial activity)
remains a challenge and needs to be solved. Herein, a metal ion cross-linking
reinforced, double network hydrogel was formed from a 2-acrylamide-2-methylpropanesulfonic
acid (AMPS) copolymer interpenetrating κ-carrageenan (CAR),
followed by immersing the gel in a Cu2+ ion solution to
obtain an antibacterial CAR/P(AM-co-AMPS)-Cu2+ conductive hydrogel. LiCl was added as the electrolyte.
The presence of the LiCl electrolyte and sulfonated molecular chain
units not only gives the hydrogel good electrical conductivity (conductivity
up to 2.68 S/m) but also improves the sensitivity of the hydrogel
as a stress–strain sensor, with a hydrogel sensitivity GF of up to 3.76 in the 20%–100% strain range and
response time of up to 280 ms. The CAR double-helical structure and
sol–gel properties and the interaction of multiple noncovalent
bonds between polymers provide the hydrogel with excellent self-healing,
with a self-healing efficiency of 68%. In addition, the electrostatic
interaction of Cu2+ with Escherichia coli cells can inhibit their growth, exhibiting good antibacterial properties
with an inhibition circle diameter of 20.5 mm. This work could provide
an effective strategy for antibacterial multifunctional CAR-based
bionic sensors.