Designing lightweight nanostructured aerogels for high‐performance electromagnetic interference (EMI) shielding is crucial yet challenging. Ultrathin cellulose nanofibrils (CNFs) are employed for assisting in building ultralow‐density, robust, and highly flexible transition metal carbides and nitrides (MXenes) aerogels with oriented biomimetic cell walls. A significant influence of the angles between oriented cell walls and the incident EM wave electric field direction on the EMI shielding performance is revealed, providing an intriguing microstructure design strategy. MXene “bricks” bonded by CNF “mortars” of the nacre‐like cell walls induce high mechanical strength, electrical conductivity, and interfacial polarization, yielding the resultant MXene/CNF aerogels an ultrahigh EMI shielding performance. The EMI shielding effectiveness (SE) of the aerogels reaches 74.6 or 35.5 dB at a density of merely 8.0 or 1.5 mg cm
–3
, respectively. The normalized surface specific SE is up to 189 400 dB cm
2
g
–1
, significantly exceeding that of other EMI shielding materials reported so far.
Ambient‐pressure‐dried (APD) preparation of transition metal carbide/nitrides (MXene) aerogels is highly desirable yet remains highly challenging. Here, ultrathin, high‐strength‐to‐weight‐ratio, renewable cellulose nanofibers (CNFs) are efficiently utilized to assist in the APD preparation of ultralight yet robust, highly conductive, large‐area MXene‐based aerogels via a facile, energy‐efficient, eco‐friendly, and scalable freezing‐exchanging‐drying approach. The strong interactions of large‐aspect‐ratio CNF and MXene as well as the biomimetic nacre‐like microstructure induce high mechanical strength and stability to avoid the structure collapse of aerogels in the APD process. Abundant functional groups of CNFs facilitate the chemical crosslinking of MXene‐based aerogels, significantly improving the hydrophobicity, water resistance, and even oxidation stability. The ultrathin, 1D nature of the CNF renders the minimal MXenes’ interlayered gaps and numerous heterogeneous interfaces, yielding the excellent conductivity and electromagnetic interference (EMI) shielding performance of aerogels. The synergies of the MXene, CNF, and abundant pores efficiently improve the EMI shielding performance, photothermal conversion, and absorption of viscous crude oil. This work shows great promises of the APD, multifunctional MXene‐based aerogels in electromagnetic protection or compatibility, thermal therapy, and oil‐water separation applications.
Noninvasive
and seamless interfacing between the sensors and human
skin is highly desired for wearable healthcare. Thin-film-based soft
and stretchable sensors can to some extent form conformal contact
with skin even under dynamic movements for high-fidelity signals acquisition.
However, sweat accumulation underneath these sensors for long-term
monitoring would compromise the thermal-wet comfort, electrode adherence
to the skin, and signal fidelity. Here, we report the fabrication
of a highly thermal-wet comfortable and conformal silk-based electrode,
which can be used for on-skin electrophysiological measurement under
sweaty conditions. It is realized through incorporating conducting
polymers poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS)
into glycerol-plasticized silk fiber mats. Glycerol plays the role
of tuning the mechanical properties of silk fiber mats and enhancing
the conductivity of PEDOT:PSS. Our silk-based electrodes show high
stretchability (>250%), low thermal insulation (∼0.13 °C·m2·W–1), low evaporative resistance (∼23
Pa·m2·W–1, 10 times lower than
∼1.3 mm thick commercial gel electrodes), and high water-vapor
transmission rate (∼117 g·m–2·h–1 under sweaty conditions, 2 times higher than skin
water loss). These features enable a better electrocardiography signal
quality than that of commercial gel electrodes without disturbing
the heat dissipation during sweat evaporation and provide possibilities
for textile integration to monitor the muscle activities under large
deformation. Our glycerol-plasticized silk-based electrodes possessing
superior physiological comfortability may further engage progress
in on-skin electronics with sweat tolerance.
Ultralight and highly elastic reduced graphene oxide (RGO)/lignin-derived carbon (LDC) composite aerogels with aligned micron-sized pores and cell walls are prepared using a facile freeze-drying method. The presence of a small fraction of LDC in the cell walls enhances the interfacial polarization effect while almost maintaining the amount of charge carriers and conductivity of the cell walls, greatly boosting the wave absorption capability of the cell walls. RGO/LDC aerogels also show a greater number of large cell walls with better integrity than RGO aerogels, further improving the multiple reflection ability of the aligned cell walls. Synergistic effects of the multiphase cell walls and the preferred microstructures of the RGO/LDC aerogels lead to their high electromagnetic interference (EMI) shielding effectiveness of 21.3-49.2 dB at an ultralow density of 2.0-8.0 mg/cm. This corresponds to the surface-specific SE (SE divided by density and thickness) up to 53 250 dB·cm/g, which is higher than the values reported for other carbon- and metal-based shields. Furthermore, the critical roles that microstructures play in determining the EMI shielding performance are directly revealed by comparing the shielding performance in directions parallel and normal to cell walls, as well as in an in situ compression process.
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