As a functional material, conductive
hydrogel has been widely used
due to its stretchability and flexibility, especially in the field
of flexible wearable sensors. However, preparing a hydrogel sensor
with high elasticity, fatigue resistance, and low-temperature resistance
is still challenging. In this work, a novel hydrogel was synthesized
with acrylic acid and sodium p-styrene sulfonate
in an acidic solution of chitosan under ultraviolet light. Then, the
hydrogel was immersed in the sodium chloride solution to obtain a
chitosan/poly(acrylic acid-sodium p-styrene sulfonate)/sodium
chloride (CS/P(AA-co-SS)/NaCl) dual network (DN)
hydrogel. The sodium chloride caused the molecular chains of the hydrogel
to entangle. The hydrogel shows excellent mechanical properties (tensile
strength is as high as 532.2 kPa, elongation at break is as high as
620%, energy to break is 1200 kJ/m3, compressive strength
at 80% is 661 kPa, and compressive toughness is 83.5 kJ/m3) and high electrical conductivity (up to 4.5 S/m). At the same time,
the hydrogel possesses excellent resilience and fatigue resistance
due to hydrogen bonds, electrostatic interactions, and the existence
of hydrophobic domains. Moreover, the hydrogel also exhibits outstanding
frost resistance, excellent mechanical properties, and electrical
conductivity even at −20 °C. The wearable sensor made
of the CS/P(AA-co-SS)/NaCl DN hydrogel will have
high sensitivity (under 100% strain, gauge factor = 2.4) and repeatability,
which can accurately detect various movements of the human body.
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