To synthesize hydrogels that possess tensile strength and modulus together in MPas along with extensibility at high equilibrium water content (≥90 wt%) is challenging but important from the application perspective. Especially, such hydrogel compositions are useful for fabricating flexible electronics devices for subsea applications, where underwater risk‐free implementation and optimum device performance at low temperature (≈0 °C) and high hydrostatic pressure (≤20 bar) conditions is desirable. The high water content of hydrogel is necessary to facilitate ion transportation, and mechanical strength is desirable to maintain a stable electrode–electrolyte interface under load. In this study, supplementary networking of an interpenetrating polymer system strategy is utilized to develop ionic hydrogels with tensile strength and Young's modulus values up to 2 and 1.67 MPa, respectively, at high equilibrium water content value up to 96%. Cost‐effective, durable, rechargeable, and flexible batteries are fabricated using the Zn & Li ion soaked hydrogel as solid electrolyte without barrier. These batteries display minimal loss in capacity when immersed in water, deformed, exposed to flame, put under high load, and operated under low‐temperature conditions suggesting the viability for subsea application.
Hydrogels
possessing stretchability, toughness, and conductivity
together are promising candidates for soft electronics applications.
In this report, ionic grafting of poly(acryloyl hydrazide) (PAHz)–silver
(Ag) nanocomposites (NC) is used to improve the mechanical properties
and conductivity of poly(acrylamidopropanesulfonic acid)
(PAMPS) hydrogels. PAHz–Ag NCs possessing different sizes of
Ag NPs (3–40 nm) are grafted in the PAMPS hydrogel matrix via
−CONHNH3
+---–O3S ionic linkage. The resulting PAHz–Ag NC grafted hydrogels
at ∼62 wt % water content exhibited ultimate tensile strength
(UTS) and fracture energy up to ∼1.14 MPa and ∼1600
J/m2, respectively. The UTS of hydrogels was dependent
on the size of Ag NP in PAHz–Ag NCs, and the value increased
from 0.70 to 1.14 MPa with the decrease in Ag NP size from ∼40
to 5 nm. The hydrogel samples exhibited adequate skin adhesiveness
(tack adhesive strength ≈10.8 kPa), conductivity (50.5 mS/cm),
and strain sensing ability (gauge factor ≈0.9), suggesting
these samples are potentially useful for various soft electronics
applications. As a proof of concept, the hydrogels were employed as
soft electrode in an electrocardiogram (ECG) device, and the efficiency
was monitored under real-time conditions. The data exhibited noise-free
reproducible patterns of ECG with defined P, Q, R, S, and T peaks
under different locomotion of the body, suggesting the viability of
developed hydrogels for the ECG sensing applications.
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