2D materials are of particular interest in light‐to‐heat conversion, yet challenges remain in developing a facile method to suppress their light reflection. Herein, inspired by the black scales of Bitis rhinoceros, a generalized approach via sequential thermal actuations to construct biomimetic 2D‐material nanocoatings, including Ti3C2Tx MXene, reduced graphene oxide (rGO), and molybdenum disulfide (MoS2) is designed. The hierarchical MXene nanocoatings result in broadband light absorption (up to 93.2%), theoretically validated by optical modeling and simulations, and realize improved light‐to‐heat performance (equilibrium temperature of 65.4 °C under one‐sun illumination). With efficient light‐to‐heat conversion, the bioinspired MXene nanocoatings are next incorporated into solar steam‐generation devices and stretchable solar/electric dual‐heaters. The MXene steam‐generation devices require much lower solar‐thermal material loading (0.32 mg cm−2) and still guarantee high steam‐generation performance (1.33 kg m−2 h−1) compared with other state‐of‐the‐art devices. Additionally, the mechanically deformed MXene structures enable the fabrication of stretchable and wearable heaters dual‐powered by sunlight and electricity, which are reversibly stretched and heated above 100 °C. This simple fabrication process with effective utilization of active materials promises its practical application value for multiple solar–thermal technologies.
In the emerging Internet of Things, stretchable antennas can facilitate wireless communication between wearable and mobile electronic devices around the body. The proliferation of wireless devices transmitting near the human body also raises interference and safety concerns that demand stretchable materials capable of shielding electromagnetic interference (EMI). Here, an ultrastretchable conductor is fabricated by depositing a crumple-textured coating composed of 2D Ti 3 C 2 T x nanosheets (MXene) and single-walled carbon nanotubes (SWNTs) onto latex, which can be fashioned into high-performance wearable antennas and EMI shields. The resulting MXene-SWNT (S-MXene)/latex devices are able to sustain up to an 800% areal strain and exhibit strain-insensitive resistance profiles during a 500-cycle fatigue test. A single layer of stretchable S-MXene conductors demonstrate a strain-invariant EMI shielding performance of ≈30 dB up to 800% areal strain, and the shielding performance is further improved to ≈47 and ≈52 dB by stacking 5 and 10 layers of S-MXene conductors, respectively. Additionally, a stretchable S-MXene dipole antenna is fabricated, which can be uniaxially stretched to 150% with unaffected reflected power <0.1%. By integrating S-MXene EMI shields with stretchable S-MXene antennas, a wearable wireless system is finally demonstrated that provides mechanically stable wireless transmission while attenuating EM absorption by the human body.existing mobile devices. [1] To enable highperformance wireless communication between wearable sensors, displays, and data processing devices around the body, new routes to fabricating for stretchable antennas that exhibit mechanically stable performance are needed. Furthermore, the proliferation of mobile and wearable devices based on various wireless technologies, including GPS, Bluetooth, Wi-Fi, and near-field communication, is increasing the frequency and duration of the human body exposed to electromagnetic (EM) fields, which raises interference and safety concerns that may require certain suitable materials for EM protection. [2] Therefore, in addition to the growing demand for stretchable antennas, electromagnetic interference (EMI) shielding materials that are stretchable, durable, and can be integrated closely with wearable wireless technologies are needed to reduce the exposure of the human body to EM fields. Integrating such stretchable antennas with on-site EMI shields not only provides protection against EM fields, but also prevents unauthorized wireless transmission between wearable electronics and mobile devices for enhanced wireless privacy.Both wearable antennas and stretchable EMI shields face similar technological challenges, where the key materials awaiting to be developed are the stretchable conductors with high strain tolerance and strain-invariant electrical conductivities.Metals (e.g., Cu and Al) are the conventionally used materials for EMI shields and antennas on many occasions. As the trend in today's electronic devices becomes faster, lighter, and...
Sodium ion (Na)-based electrochemical systems have been extensively investigated in batteries and supercapacitors and also can be quality candidates for electrochromic (EC) devices. However, poor diffusion kinetics and severe EC performance degradation occur during the intercalation/deintercalation processes because the ionic radii of Na are larger than those of conventional intercalation ions. Here, through intentional design of ion-transport channels in metal-organic frameworks (MOFs), Na serves as an efficient intercalation ion for incorporation into a nanostructured electrode with a high diffusion coefficient of approximately 10 cm s. As a result, the well-designed MOF-based EC device demonstrates desirable Na EC performance, including fast switching speed, multicolor switching, and high stability. A smart "quick response code" display is fabricated using a mask-free laser writing method for application in the "Internet of Things". In addition, the concept of ion transport pathway design can be widely adopted for fabricating high-performance ion intercalation materials and devices for consumer electronics.
Electrochemical capacitor systems based on Al ions can offer the possibilities of low cost and high safety, together with a three-electron redox-mechanism-based high capacity, and thus are expected to provide a feasible solution to meet ever-increasing energy demands. Here, highly efficient Al-ion intercalation into W O nanowires (W O NWs) with wide lattice spacing and layered single-crystal structure for electrochemical storage is demonstrated. Moreover, a freestanding composite film with a hierarchical porous structure is prepared through vacuum-assisted filtration of a mixed dispersion containing W O NWs and single-walled carbon nanotubes. The as-prepared composite electrode exhibits extremely high areal capacitances of 1.11-2.92 F cm and 459 F cm at 2 mA cm , enhanced electrochemical stability in the Al electrolyte, as well as excellent mechanical properties. An Al-ion-based, flexible, asymmetric electrochemical capacitor is assembled that displays a high volumetric energy density of 19.0 mWh cm at a high power density of 295 mW cm . Finally, the Al-ion-based asymmetric supercapacitor is used as the power source for poly(3-hexylthiophene)-based electrochromic devices, demonstrating their promising capability in flexible electronic devices.
Two-dimensional MXene materials have demonstrated attractive electrical and electrochemical properties in energy storage applications. Adding stretchability to MXene remains challenging due to its high mechanical stiffness and weak intersheet interaction, so the assembling techniques for mechanically stable MXene architectures require further development. We report a simple fabrication by harnessing the interfacial instability to generate higher dimensional MXene nanocoatings capable of programmed crumpling/unfolding. A sequential patterning approach enabled the design of sequence-dependent MXene textures across multiple length scales, which were utilized for controllable wetting surfaces and high-areal-capacitance electrodes. We next transferred the crumpled MXene nanocoating onto an elastomer to fabricate an MXene/elastomer electrode with high stretchability. The accordion-like MXene can be reversibly folded/unfolded and still preserve efficient specific capacitances. We further fabricated asymmetric MXene supercapacitors, and the devices demonstrated efficient electrochemical performance and large deformability (180° bendability, 100% stretchability). Our texturing techniques can be applied to large MXene families for designing stretchable architectures in wearable electronics.
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