A wearable and flexible pressure sensor is essential to the realization of personalized medicine through continuously monitoring an individual’s state of health and also the development of a highly ...intelligent robot. A flexible, wearable pressure sensor is fabricated based on novel single-wall carbon nanotube /tissue paper through a low-cost and scalable approach. The flexible, wearable sensor showed superior performance with concurrence of several merits, including high sensitivity for a broad pressure range and an ultralow energy consumption level of 10–6 W. Benefited from the excellent performance and the ultraconformal contact of the sensor with an uneven surface, vital human physiological signals (such as radial arterial pulse and muscle activity at various positions) can be monitored in real time and in situ. In addition, the pressure sensors could also be integrated onto robots as the artificial skin that could sense the force/pressure and also the distribution of force/pressure on the artificial skin.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Human voice recognition systems (VRSs) are a prerequisite for voice-controlled human-machine interfaces (HMIs). In order to avoid interference from unexpected background noises, skin-attachable VRSs ...are proposed to directly detect physiological mechanoacoustic signals based on the vibrations of vocal cords. However, the sensitivity and response time of existing VRSs are bottlenecks for efficient HMIs. In addition, water-based contaminants in our daily lives, such as skin moisture and raindrops, normally result in performance degradation or even functional failure of VRSs. Herein, we present a skin-attachable self-cleaning ultrasensitive and ultrafast acoustic sensor based on a reduced graphene oxide/polydimethylsiloxane composite film with bioinspired microcracks and hierarchical surface textures. Benefitting from the synergetic effect of the spider-slit-organ-like multiscale jagged microcracks and the lotus-leaf-like hierarchical structures, our superhydrophobic VRS exhibits an ultrahigh sensitivity (gauge factor, GF = 8699), an ultralow detection limit (ε = 0.000 064%), an ultrafast response/recovery behavior, an excellent device durability (>10 000 cycles), and reliable detection of acoustic vibrations over the audible frequency range (20–20 000 Hz) with high signal-to-noise ratios. These superb performances endow our skin-attachable VRS with anti-interference perception of human voices with high precision even in noisy environments, which will expedite the voice-controlled HMIs.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Fast, simple, cost‐efficient, eco‐friendly, and design‐flexible patterning of high‐quality graphene from abundant natural resources is of immense interest for the mass production of next‐generation ...graphene‐based green electronics. Most electronic components have been manufactured by repetitive photolithography processes involving a large number of masks, photoresists, and toxic etchants; resulting in slow, complex, expensive, less‐flexible, and often corrosive electronics manufacturing processes to date. Here, a one‐step formation and patterning of highly conductive graphene on natural woods and leaves by programmable irradiation of ultrafast high‐photon‐energy laser pulses in ambient air is presented. Direct photoconversion of woods and leaves into graphene is realized at a low temperature by intense ultrafast light pulses with controlled fluences. Green graphene electronic components of electrical interconnects, flexible temperature sensors, and energy‐storing pseudocapacitors are fabricated from woods and leaves. This direct graphene synthesis is a breakthrough toward biocompatible, biodegradable, and eco‐friendlily manufactured green electronics for the sustainable earth.
Ultrashort femtosecond laser pulses enable one‐step patterning of highly conductive graphene electronics on natural woods and leaves in ambient air. Arbitrary graphene patterns can be directly formed on thin, flexible, and heat‐sensitive dried leaves without any pre‐treatment by femtosecond laser pulses. This direct graphene synthesis could be a breakthrough toward biocompatible, biodegradable, and eco‐friendlily‐manufactured green electronics for a sustainable earth.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Noncontact electronic skin (e-skin), which possesses superior long-range and high-spatial-resolution sensory properties, is becoming indispensable in fulfilling the emulation of human sensation via ...prosthetics. Here, we present an advanced design and fabrication of all-graphene-based highly flexible noncontact e-skins by virtue of femtosecond laser direct writing (FsLDW). The photoreduced graphene oxide patterns function as the conductive electrodes, whereas the pristine graphene oxide thin film serves as the sensing layer. The as-fabricated e-skins exhibit high sensitivity, fast response–recovery behavior, good long-term stability, and excellent mechanical robustness. In-depth analysis reveals that the sensing mechanism is attributed to proton and ionic conductivity in the low and high humidity conditions, respectively. By taking the merits of the FsLDW, a 4 × 4 sensing matrix is facilely integrated in a single-step, eco-friendly, and green process. The light-weight and in-plane matrix shows high-spatial-resolution sensing capabilities over a long detection range in a noncontact mode. This study will open up an avenue to innovations in the noncontact e-skins and hold a promise for applications in wearable human–machine interfaces, robotics, and bioelectronics.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Plasmon-assisted visible light photocatalysis presents a possible solution for direct solar-to-fuel production. Here we investigate the plasmon-enhanced photocatalytic water splitting using different ...TiO2/Au electrode structures. Experimental data demonstrates that the Au embedded in TiO2 (Au-in-TiO2) electrode greatly outperforms the Au sitting on TiO2 (Au-on-TiO2) electrode. Numerical simulation shows that the local electric field is very intense in the semiconductor near Au nanoparticles, which causes the enhancement of electron–hole pair generation. A 3D Au-embedded TiO2 structure is thus proposed to further improve the light absorption and photocatalytic performance.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Carbon dioxide adducts from polypropylene glycol (PPG)-grafted polyethylenimines (PEIs) are promising alternatives to the traditional, climate-changing blowing agents for polyurethanes (PUs). Their ...commercialization is hindered by the fact that they can restore their original polyamine structure when releasing CO2 to blow PUs and that the extent to which the restored amine groups react with the isocyanate (NCO) groups in the foaming mixture is still not clear. The extent of this reaction was quantitatively investigated by FTIR and 1H NMR spectroscopy. The increase in the PPG side chain length or in the grafting rate reduced the reaction extent of the restored amines due to increased steric hindrance. The increase in the PEI backbone molecular weight decreased the macromolecular mobility, which somewhat inhibited a full contact between the restored amine groups and the NCO groups and thus caused a decrease in the reaction extent as well. Overall, the reaction extents of the blowing agent amine groups, ranging from 0.4% to 1.5%, were too low to change the foaming process chemically. In conclusion, these CO2-releasing blowing agents can be technically regarded as physical blowing agents.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The increasing demand for wearable optoelectronics in biomedicine, prosthetics, and soft robotics calls for innovative and transformative technologies that permit facile fabrication of compact and ...flexible photodetectors with high performance. Herein, by developing a single‐step selective laser writing strategy that can finely tailor material properties through incident photon density control and lead to the formation of hierarchical hybrid nanocomposites, e.g., reduced graphene oxide (rGO)–zinc oxide (ZnO), a highly flexible and all rGO–ZnO hybrid‐based photodetector is successfully constructed. The device features 3D ultraporous hybrid films with high photoresponsivity as the active detection layer, and hybrid nanoflakes with superior electrical conductivity as interdigitated electrodes. Benefitting from enhanced photocarrier generation because of the ultraporous film morphology, efficient separation of electron–hole pairs at rGO–ZnO heterojunctions, and fast electron transport by highly conductive rGO nanosheets, the photodetector exhibits high, linear, and reproducible responsivities to a wide range of ultraviolet (UV) intensities. Furthermore, the excellent mechanical flexibility and robustness enable the photodetector to be conformally attached to skin, thus intimately monitoring the exposure dosage of human body to UV light for skin disease prevention. This study advances the fabrication of flexible optoelectronic devices with reduced complexity, facilitating the integration of wearable optoelectronics and epidermal systems.
A single‐step selective laser writing strategy is developed to directly fabricate highly flexible in‐plane photodetectors based on hierarchical reduced graphene oxide (rGO)–zinc oxide (ZnO) hybrid nanocomposites with tunable electrical and optoelectrical properties. The photodetector exhibits high, linear, and reproducible responsivities to a wide range of ultraviolet intensities at a low operation voltage, and has excellent mechanical robustness.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The ever‐growing demand in modern power systems calls for the innovation in electrochemical energy storage devices so as to achieve both supercapacitor‐like high power density and battery‐like high ...energy density. Rational design of the micro/nanostructures of energy storage materials offers a pathway to finely tailor their electrochemical properties thereby enabling significant improvements in device performances and enormous strategies have been developed for synthesizing hierarchically structured active materials. Among all strategies, the direct conversion of precursor templates into target micro/nanostructures through physical and/or chemical processes is facile, controllable, and scalable. Yet the mechanistic understanding of the self‐templating method is lacking and the synthetic versatility for constructing complex architectures is inadequately demonstrated. This review starts with the introduction of five main self‐templating synthetic mechanisms and the corresponding constructed hierarchical micro/nanostructures. Subsequently, the structural merits provided by the well‐defined architectures for energy storage are elaborately discussed. At last, a summary of current challenges and future development of the self‐templating method for synthesizing high‐performance electrode materials is also presented.
The micro/nanostructure design via self‐templating method offers a viable way to significantly improve the electrochemical performances of functional materials. This review introduces five main self‐templating mechanisms and compares the merits of different micro/nanostructures for energy storage. Furthermore, a summary of current challenges and the prospect of self‐templating strategy for constructing high‐performance electrode materials are also presented.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Lithium-sulfur (Li-S) batteries as power supply systems possessing a theoretical energy density of as high as 2600 Wh kg
are considered promising alternatives toward the currently used lithium-ion ...batteries (LIBs). However, the insulation characteristic and huge volume change of sulfur, the generation of dissolvable lithium polysulfides (LiPSs) during charge/discharge, and the uncontrollable dendrite formation of Li metal anodes render Li-S batteries serious cycling issues with rapid capacity decay. To address these challenges, extensive efforts are devoted to designing cathode/anode hosts and/or modifying separators by incorporating functional materials with the features of improved conductivity, lithiophilic, physical/chemical capture ability toward LiPSs, and/or efficient catalytic conversion of LiPSs. Among all candidates, molybdenum-based (Mo-based) materials are highly preferred for their tunable crystal structure, adjustable composition, variable valence of Mo centers, and strong interactions with soluble LiPSs. Herein, the latest advances in design and application of Mo-based materials for Li-S batteries are comprehensively reviewed, covering molybdenum oxides, molybdenum dichalcogenides, molybdenum nitrides, molybdenum carbides, molybdenum phosphides, and molybdenum metal. In the end, the existing challenges in this research field are elaborately discussed.
Non‐invasive human‐machine interactions (HMIs) are expected to be promoted by epidermal tactile receptive devices that can accurately perceive human activities. In reality, however, the HMI ...efficiency is limited by the unsatisfactory perception capability of mechanosensors and the complicated techniques for device fabrication and integration. Herein, a paradigm is presented for high‐throughput fabrication of multimodal epidermal mechanosensors based on a sequential “femtosecond laser patterning‐elastomer infiltration‐physical transfer” process. The resilient mechanosensor features a unique hybrid sensing layer of rigid cellular graphitic flakes (CGF)‐soft elastomer. The continuous microcracking of CGF under strain enables a sharp reduction in conductive pathways, while the soft elastomer within the framework sustains mechanical robustness of the structure. As a result, the mechanosensor achieves an ultrahigh sensitivity in a broad strain range (GF of 371.4 in the first linear range of 0–50%, and maximum GF of 8922.6 in the range of 61–70%), a low detection limit (0.01%), and a fast response/recovery behavior (2.6/2.1 ms). The device also exhibits excellent sensing performances to multimodal mechanical stimuli, enabling high‐fidelity monitoring of full‐range human motions. As proof‐of‐concept demonstrations, multi‐pixel mechanosensor arrays are constructed and implemented in a robot hand controlling system and a security system, providing a platform toward efficient HMIs.
A multimodal epidermal mechanosensor with superior detectability is achieved by a high‐throughput “femtosecond laser patterning‐elastomer infiltration‐physical transfer” manufacturing method. The continuous microcracking of the rigid conductive frameworks results in ultrahigh strain sensitivities, while the soft elastomer filler renders the device with a wide sustainable strain range. The multimodal mechanosensor can acquire diverse physiological and physical signals in a high‐fidelity fashion.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
PDF
