Wearable All-Fabric Hybrid Energy Harvester to Simultaneously Harvest Radiofrequency and Triboelectric Energy.

Distributed micro-energy harvesting devices offer the flexibility, sustainability, and multi-scenario applicability that will be critical to wearable electronic products in the Internet of Things. The radiofrequency and triboelectric (RF-TE) hybrid energy harvester (HEH) concept and prototype is presented for the first time, to simultaneously capture the energy from ambient electromagnetic waves and biological motions. The proposed hybrid energy harvesting system consists of a wearable rectenna, a triboelectric nanogenerator (TENG), and a power management circuit (PMC). Among them, the all-fabric rectenna exhibits good impedance matching characteristics in the ISM frequency. The flexible TENG unit can generate a maximum power density of 0.024 µW cm-2. The designed multifunctional fabric-based PMC can considerably enhance the controllability of harvested hybrid energy. Additionally, a normalizable fabric circuit board quasi surface mount technology (FCB-SMT) is proposed to integrate all modules on the same fabric substrate in one step, making the entire system superior mechanical robustness. The proposed wearable fabric-based RF-TE hybrid energy harvester is capable of successfully driving consumer electronics (such as sensors, watches, etc.). It provides a new energy solution strategy for self-powered wearable electronic devices and is anticipated to encourage the efficient utilization of renewable energy.

2D PtSe2 Enabled Wireless Wearable Gas Monitoring Circuits with Distinctive Strain-Enhanced Performance.

The application of 2D materials-based flexible electronics in wearable scenarios is limited due to performance degradation under strain fields. In contrast to its negative role in existing transistors or sensors, herein, we discover a positive effect of strain to the ammonia detection in 2D PtSe2. Linear modulation of sensitivity is achieved in flexible 2D PtSe2 sensors via a customized probe station with an in situ strain loading apparatus. For trace ammonia absorption, a 300% enhancement in room-temperature sensitivity (31.67% ppm-1) and an ultralow limit of detection (50 ppb) are observed under 1/4 mm-1 curvature strain. We identify three types of strain-sensitive adsorption sites in layered PtSe2 and pinpoint that basal-plane lattice distortion contributes to better sensing performance resulting from reduced absorption energy and larger charge transfer density. Furthermore, we demonstrate state-of-the-art 2D PtSe2-based wireless wearable integrated circuits, which allow real-time gas sensing data acquisition, processing, and transmission through a Bluetooth module to user terminals. The circuits exhibit a wide detection range with a maximum sensitivity value of 0.026 V·ppm-1 and a low energy consumption below 2 mW.

Flexible two-dimensional MXene-based antennas.

With the growing development of the Internet of things, wearable electronic devices have been extensively applied in civilian and military fields. As an essential component of data transmission in wearable electronics, a flexible antenna is one of the key aspects of research. Conventional metal antennas suffer from a large skin depth, and cannot satisfy the requirements of wearable electronics such as light weight, flexibility, and thinness. Recently, a group of two-dimensional metallic metal carbides (named MXenes) have been explored as building blocks for high-performance flexible antennas with excellent flexibility and superior mechanical strength. The appearance of hydrophilic functional groups at the surface of a MXene allows simple, scalable, and environmentally friendly manufacturing of MXene-based antennas. In this minireview, some pioneering works of MXene-based flexible radio frequency components are summarized, and the existing bottlenecks and the future trends of this promising field are discussed.

A Study on the Dynamic Tunning Range of CVD Graphene at Microwave Frequency: Determination, Prediction and Application.

In recent years, graphene has shown great application prospects in tunable microwave devices due to its tunable conductivity. However, the electromagnetic (EM) properties of graphene, especially the dynamic tunning characteristics, are largely dependent on experimental results, and thus are unable to be effectively predicted according to growth parameters, which causes great difficulties in the design of graphene-based tunable microwave devices. In this work, we systematically explored the impact of chemical vapor deposition (CVD) parameters on the dynamic tunning range of graphene. Firstly, through improving the existing waveguide method, the dynamic tunning range of graphene can be measured more accurately. Secondly, a direct mathematical model between growth parameters and the tunning range of graphene is established. Through this, one can easily obtain needed growth parameters for the desired tunning range of graphene. As a verification, a frequency tunable absorber prototype is designed and tested. The good agreement between simulation and experimental results shows the reliability of our mathematic model in the rapid design of graphene-based tunable microwave devices.

Stretchable and self-healable spoof plasmonic meta-waveguide for wearable wireless communication system.

Microwave transmission lines in wearable systems are easily damaged after frequent mechanical deformation, posing a severe threat to wireless communication. Here, we report a new strategy to achieve stretchable microwave transmission lines with superior reliability and durability by integrating a self-healable elastomer with serpentine-geometry plasmonic meta-waveguide to support the spoof surface plasmon polariton (SSPP). After mechanical damage, the self-healable elastomer can autonomously repair itself to maintain the electromagnetic performance and mechanical strength. Meanwhile, the specially designed SSPP structure exhibits excellent stability and damage resistance. Even if the self-healing process has not been completed or the eventual repair effect is not ideal, the spoof plasmonic meta-waveguide can still maintain reliable performance. Self-healing material enhances strength and durability, while the SSPP improves stability and gives more tolerance to the self-healing process. Our design coordinates the structural design with material synthesis to maximize the advantages of the SSPP and self-healing material, significantly improving the reliability and durability of stretchable microwave transmission lines. We also perform communication quality experiments to demonstrate the potential of the proposed meta-waveguide as interconnects in future body area network systems.

Nano-antenna enhanced waveguide integrated light source based on an MIS tunnel junction.

Ultrafast electro-optical conversion at nanoscale is of fundamental interest for information transfer and optical interconnects. Light emission from a quantum tunnel junction provides an opportunity owing to its unique capability of ultrafast response and small footprint. However, the main challenge to the wide adoption of the tunnel junction is its low emission efficiency caused by the low inelastic electron tunneling proportion and radiation efficiency. In this Letter, an electrically driven silicon light source with its efficiency enhanced by using a nano-antenna in a metal-insulator-semiconductor junction is proposed. Strong plasmon confinement in the nano-antenna provides large local density of optical states and bridges the wave vector mismatch between nanoscale volume field confinement and far-field radiation. Two orders of magnitude of emission enhancement are achieved over typical planar MIS junctions.

Low-energy high-speed plasmonic enhanced modulator using graphene.

Graphene, as a type of flexible and electrically adjustable two-dimensional material, has exceptional optical and electrical properties that make it possible to be used in modulators. However, the poor interaction between optical fields and a single atom graphene layer prevents the easy implementation of graphene modulators. Currently available devices often require a larger overlap area of graphene to obtain the desired phase or amplitude modulation, which results in a rather large footprint and high capacitance and consequently increases the energy consumption and reduces the modulation speed. In this paper, a localized plasmonic-enhanced waveguide modulator with high-speed tunability using graphene is proposed for telecommunication applications. Strong modulation of the transmission takes place due to the enhanced interaction between the ultrathin plasmon patches and the graphene, when the plasmons are tuned on- and off-resonance by the gate-tunable graphene. A 400 GHz modulation rate using low gated-voltages with an active device area of 0.2 µm2 and a low consumption of only 0.5 fJ/bit is achieved, which paves the way for ultrafast low-energy optical waveguide modulation and switching.

Enhanced Bandwidth of High Directive Emission Fabry-Perot Resonator Antenna with Tapered Near-Zero Effective Index Using Metasurface.

In this paper, a novel explanation on high directive emission of Fabry-Perot resonator antenna with subwavelength metasurface is proposed. Based on image theory and effective constitutive parameter retrieval, the whole Fabry-Perot resonant cavity structure composed of a single-layer metasurface with square ring element and a PEC ground plate can be acted as an effective metamaterial media with very low refractive index (near zero index). According to Snell's theory, this property can be used to enhance the directive emission. Based on this, with tapered size square ring unitcell, the overlapped bandwidth in which the effective refractive index is near to zero is obtained to widen the bandwidth of high directive emission. It is demonstrated that the maximum of directivity is nearly approaching to 19 dBi, and its 3-dB bandwidth can be improved to 19.5%. A final prototype has been fabricated and measured to validate the proposed design concept. The measured 3-dB gain bandwidth is approximately 20.3% with a peak gain of 17.9 dBi. These results indicate the feasibility of such kind of antenna for broadband and high directivity applications simultaneously.

Waveguide-coupled hybrid plasmonic modulator based on graphene.

In this paper, we propose a low-transmission-loss, high-speed, graphene-based electro-absorption modulator with a hybrid plasmonic waveguide at 1.55 µm. In the proposed device, double-layer graphene is placed on top of the horizontal hybrid plasmonic waveguide to enhance the light-graphene interaction. The adjustment of the in-plane permittivity of the anisotropy graphene causes a significant modulation of the absorption at the operating bandwidth of 0.4 THz, with modulation length of 8.5 µm and modulator footprint of 1.6 µm2. A taper silicon coupler is used for waveguide coupling, and 80% coupling efficiency is achieved. In addition, the modulation potential on a smaller footprint is further shown.

Limitation of fluorescence spectrophotometry in the measurement of naphthenic acids in oil sands process water.

Fluorescence spectrophotometry has been proposed as a quick screening technique for the measurement of naphthenic acids (NAs). To evaluate the feasibility of this application, the fluorescence emission spectra of NAs extracted from three oil sands process water sources were compared with that of commercial NAs. The NAs resulting from the bitumen extraction process cannot be differentiated because of the similarity of the fluorescence spectra. Separation of the fluorescent species in NAs using high performance liquid chromatography with fluorescence detector proved unsuccessful. The acidic fraction of NAs is fluorescent but the basic fraction of NAs is not fluorescent, implying that aromatic acids in NAs give rise to the fluorescent signals. The concentrations of NAs in oil sands process water were measured by Fourier transform infrared spectroscopy (FTIR), fluorescence spectrophotometry and ultra high performance liquid chromatography-time of flight/mass spectrometry (UPLC-TOF/MS). Commercial Merichem and Kodak NAs are the best standards to use when measuring NAs concentration with FTIR and fluorescence spectrophotometry. In addition, the NAs concentrations measured by fluorescence spectrophotometry are about 30 times higher than those measured by FTIR and UPLC-TOF/MS. The findings in this study underscore the limitation of fluorescence spectrophotometry in the measurement of NAs.

Efficient and rapid uptake of magnetic carbon nanotubes into human monocytic cells: implications for cell-based cancer gene therapy.

Monocyte-based gene therapies in cancer have been hampered by either the resistance of these cells to non-viral molecular delivery methods or their poor trafficking to the tumor site after their ex vivo manipulations. Magnetic nanoparticles (MNP)-loaded genetically engineered monocytes can efficiently delivered to tumor site by external magnetic field, but they are not ideal delivery tools due to their spherical shape. Hence, we have investigated the cellular uptake efficiency and cytotoxicity of fluorescein isothiocyanate (FITC)-labelled magnetic carbon nanotubes (FITC-mCNT) in human monocytic leukemia cell line THP-1 for application in cell-based gene therapy against cancer. Uptake of FITC-mCNT into THP-1 cells reached 100% only 1 h after the delivery. Confocal imaging confirmed that FITC-mCNT entered the cell cytoplasm and even into the nucleus. FITC-mCNT uptake did not compromise cell viability. This delivery system might therefore enhance cell-based cancer gene therapies.

Magnetic carbon nanotube labelling for haematopoietic stem/progenitor cell tracking.

Haematopoietic stem and progenitor cell (HSPC) research has significantly contributed to the understanding and harnessing of haematopoiesis for regenerative medicine. However, the methodology for real-time tracking HSPC in vivo is still lacking, which seriously restricts the progress of research. Recently, magnetic carbon nanotubes (mCNT) have generated great excitement because they have been successfully used as vehicles to deliver a lot of biomolecules into various cells. There is, however, no report about mCNT being used for tracking HSPC. In this paper, we investigated the uptake efficiency of fluorescein-isothiocyanate-labelled mCNT (FITC-mCNT) into HSPC and their effect on the cytotoxicity and differentiation of HSPC. We found that cellular uptake of FITC-mCNT was concentration-and time-dependent. The uptake of FITC-mCNT into HSPC reached up to 100% with the highest mean fluorescence (MF). More importantly, efficient FITC-mCNT uptake has no adverse effect on the cell viability, cytotoxicity and differentiation of HSPC as confirmed by colony-forming unit assay (CFU). In conclusion, the results reported here suggest the further tailoring of mCNT for their use in HSPC labelling/tracking in vivo or gene delivery into HSPC.

Synthesis of hydrophobic derivatives of the G/\C base for rosette nanotube self-assembly in apolar media.

Eleven self-complementary G/\C derivatives bearing hydrophobic moieties were synthesized and characterized. One representative derivative from this family was shown to self-assemble into rosette nanotubes in hexane and form Langmuir-Blodgett films at the air-water interface.

One step cascade synthesis of 4,5-disubstituted-1,2,3-(NH)-triazoles.

A Lewis base-catalyzed three-component cascade reaction was developed for the synthesis of 4,5-disubstituted-1,2,3-(NH)-triazoles. More than 25 new (NH)-triazoles were prepared in good to excellent yields under mild conditions. The availability of the C-4 vinyl group allows easy conversion into other triazole derivatives.

Mitsunobu coupling of nucleobases and alcohols: an efficient, practical synthesis for novel nonsugar carbon nucleosides.

A simple facile synthesis of substituted purine derivatives has been developed by using Mitsunobu conditions for an alcohol and a respective nucleobase. A wide range of alcohols produces good to excellent yield (>90%). The resulting purine analogues show good regioselectivity with N-9 substitution as the dominant products in most of the cases. Application of diastereospecific alcohols reveals a complete inversion of the carbon stereogenic center giving a single diastereomer. More than two dozen novel nucleobase derivatives have been prepared in high yield.