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Zhou et al. Soft Sci. 2026, 6, 10 Page 13 of 47

hydrothermal synthesis, with the structure and preparation process shown in Figure 5C [115] . This fiber
membrane exhibits excellent hydrophilicity and ionization capability, delivering a high V of 0.65 V and
oc
short-circuit current (I ) of 2.9 μA. The electrical performance of the constructed device surpasses most
sc
previously reported devices. Zhu et al. further utilized inexpensive, easily processed whey protein to develop
a tunable power-generating layer by modulating its surface charge and hydrophilicity through pH control
[Figure 5D] . This protein-based film achieves a maximum voltage output of 1.45 V at 40% RH and exhibits
[40]
excellent flexibility, making it suitable for applications such as wearable devices and medical patches. Protein
nanofibers, as a class of biomass materials with controllable properties and sustainable sources, show great
promise for the fabrication of power-generating layers.

Unlike most existing devices that generate electricity only intermittently, equipment built using microbial
nano-protein wires can achieve continuous and stable electrical output. Liu et al. fabricated a thin film using
nano-protein filaments extracted from Sulfuribacter, which consistently generated a voltage of 0.5 V and a
current density of 17 μA·cm at a thickness of only 7 μm [116] . The exceptional biocompatibility and
-2
self-assembly properties of whole-cell Geobacter sulfurreducens (G.S.) simplify device fabrication, eliminating
the need for complex multilayer structures [117,118] . As shown in Figure 5E, integrating G.S. with photosystem II
(PSII) enables simultaneous energy harvesting from both moisture and sunlight, providing a viable strategy
for enhancing the performance of hybrid moisture-powered devices [119] . These findings demonstrate the
significant potential of microbial protein wires for constructing long-term stable, environmentally adaptive
power-generation systems.

Composite materials
Composite materials are created by combining components with different properties at the nano- or
molecular scale, resulting in superior characteristics unattainable by any single material. This precisely meets
the requirements for the humidity-powered functional layer [120,121] . By leveraging the synergistic effects of
multicomponent functionality, a single functional layer simultaneously achieves multiple capabilities:
efficient ion supply, rapid water transport, and stable mechanical support. Through adjustments to the
proportions, morphology, and interconnection methods of composite components, high power generation
performance, robust stability, and extended service life are maintained . The composite construction of a
[122]
multi-scale, multi-level pore network structure enables seamless integration from rapid water uptake to
efficient power generation, maximizing the utilization of water’s chemical potential energy while optimizing
transport pathways and charge transfer efficiency. By combining the characteristics of different materials,
composite materials complement each other, efficiently adsorb water molecules from the air, and dissociate
free ions [123] . This approach improves the output stability of MEGT devices across a wide range of
temperatures and humidity and enhances device longevity, meeting the demands of diverse practical
application scenarios . Many inorganic materials have surfaces enriched with active sites that can adsorb
[85]
and activate water molecules, facilitating efficient charge transport . In Figure 6A, Huang et al. designed an
[124]
MEG device based on a GO and sodium polyacrylate (PAAS) composite power generation layer, which
operates across -25 to 50 °C and 5% RH-95% RH, enabling effective ion dissociation and transport . Huang
[82]
et al. developed a high-performance device integrating silica (SiO ) nanofibers, SA, and rGO substrates [125] .
2
SA provides abundant Ocfgs with hygroscopic properties, while rGO offers a 2D nanosheet structure. SiO 2
nanofibers facilitate ion migration, enabling the composite to demonstrate excellent environmental
adaptability. Carbonized polymer dots (CPDs) have a polymer/carbon hybrid structure with rich functional
groups. Li et al. constructed a flexible functional layer based on phosphate-rich CPDs (PA-CPDs) . Figure
[47]
6B illustrates the fabrication process of the PA-CPD-based flexible device. By integrating PA-CPDs with an
active liquid metal (LM) top electrode, the device achieves high voltage output and favorable current density.
Liu et al. designed a water-light complementary power generation device using a hydrogel fabric composed
of PSS, GO, glycerol (GI), and PVA (PSS/GO/GI/PVA@Fab) as the functional layer with asymmetric