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Page 10 of 47 Zhou et al. Soft Sci. 2026, 6, 10

Organic materials
The core advantage of organic polymers lies in their exceptional molecular designability and rich interfacial
interactions, enabling them to participate more precisely and efficiently in the mechanisms of the
power-generating layer. Under the influence of water molecules, ionizable functional groups spontaneously
dissociate, releasing a large number of ions and providing a high concentration of free charge carriers for the
ion gradient diffusion mechanism [105] . The hydrophilic-hydrophobic microphase-separated structure
effectively regulates the adsorption and transport kinetics of water. Upon water absorption, polymer
segments exhibit flexibility and undergo swelling behavior, forming dynamically interconnected nanoscale
hydration channels that facilitate rapid ion migration [106] . Furthermore, polymers can be processed into
large-area, uniform, ultra-thin functional films on flexible substrates through various fabrication methods,
enhancing their practical applications. Organic polymers, with their tunable molecular structures, excellent
processability, and high flexibility, have become one of the ideal materials for MEGT devices. Their
properties can be further optimized through chemical modification to meet the demands of diverse
application scenarios. Polystyrene sulfonate (PSS), polyacrylamide (PAM), and sodium alginate (SA) are
widely employed in the power-generating layers of MEGTs due to their functional characteristics [107] . Xu
et al. employed functional group-rich poly(4-benzenesulfonic acid) (PSSA) as the power-generating layer
material, combined with a porous top electrode to enhance water absorption capacity [Figure 4A] [108] . The
PSSA film was prepared via a direct casting method, enabling proton-directed migration and electrical
energy output in humid environments. To broaden the application scenarios of devices, Shen et al.
developed a sandwich-structured engineered hydrogel by embedding citric acid (CA) into polyglutamic acid
(PGA) chains as the backbone and coating it with a waterproof breathable film [Figure 4B] . This structure
[54]
permits water vapor permeation while blocking liquid water, significantly enhancing the device’s operational
capability in underwater environments. By effectively isolating negative ions to promote charge separation,
the device spontaneously outputs a voltage of 0.55 V and a current density of 130 μA·cm -2[54] . These studies
demonstrate the potential of organic polymers in achieving high-performance, multi-scenario-adaptable
moisture-powered devices.

Organic polymer composite power-generating layers can effectively enhance the overall performance of
devices through synergistic effects between materials. Compared to single-material systems, composite
structures demonstrate advantages in chemical stability and environmental adaptability. Wang et al.
designed a bilayer polymer film (BPF) electrolyte based on the sequential stacking of a polycationic film
[poly(diallyl dimethyl ammonium chloride) (PDDA)] with a polyanionic film [a mixture of PSS and
polyvinyl alcohol (PVA) films (PSSA)] [Figure 4C] [105] . This dual-carrier system, integrated through
sequential stacking, achieved a high voltage output exceeding 1,000 V, demonstrating the potential of
composite structures for functional integration and performance enhancement. In the field of green material
development, Yang et al. constructed a supramolecular hydrogen power-generating layer based on PVA and
SA [Figure 4D] [109] . This material combines biocompatibility, degradability, and processing convenience.
Coupled with an asymmetric electrode structure, it enables high-performance, environmentally friendly
energy devices. Through asymmetric moisture absorption and interactions between water molecules and the
functional layer, a single unit can generate an open-circuit voltage (V ) of approximately 1.30 V. These
oc
studies demonstrate significant progress in achieving high-performance, high-voltage output, and
environmentally sustainable humidity-powered devices through composite polymer strategies.

To address the current limitations of most MEGT devices, which rely on a single power generation
mechanism and exhibit constrained output performance, researchers have conducted a series of innovative
studies employing biomimetic design and material composite strategies. Inspired by plant water uptake
mechanisms, Cheng et al. synthesized a flexible, scalable PAM hydrogel-based device using acrylamide
(AAm) and phytic acid (PA) as raw materials via ultraviolet polymerization with a photosensitizer [Figure 4E] .
[55]