Mengmeng Liu

Wearable Self‐Charging Power Textile Based on Flexible Yarn Supercapacitors and Fabric Nanogenerators

A novel and scalable self-charging power textile is realized by combining yarn supercapacitors and fabric triboelectric nanogenerators as energy-harvesting devices.

Ultrastretchable, transparent triboelectric nanogenerator as electronic skin for biomechanical energy harvesting and tactile sensing

Stretchable, transparent nanogenerator enabled by ionic hydrogel converts motion energy into electricity and senses touch pressure. Rapid advancements in stretchable and multifunctional electronics impose the challenge on corresponding power devices that they should have comparable stretchability and functionality. We report a soft skin-like triboelectric nanogenerator (STENG) that enables both biomechanical energy harvesting and tactile sensing by hybridizing elastomer and ionic hydrogel as the electrification layer and electrode, respectively. For the first time, ultrahigh stretchability (uniaxial strain, 1160%) and transparency (average transmittance, 96.2% for visible light) are achieved simultaneously for an energy-harvesting device. The soft TENG is capable of outputting alternative electricity with an instantaneous peak power density of 35 mW m−2 and driving wearable electronics (for example, an electronic watch) with energy converted from human motions, whereas the STENG is pressure-sensitive, enabling its application as artificial electronic skin for touch/pressure perception. Our work provides new opportunities for multifunctional power sources and potential applications in soft/wearable electronics.

Microstructure and optical properties of ultra-thin zirconia films prepared by nitrogen-assisted reactive magnetron sputtering

High-k ZrO2 films were prepared by nitrogen-assisted direct current reactive magnetron sputtering on n-type silicon (100). The microstructure and optical properties in relation to thermal budgets were investigated. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical states. Atomic force microscopy (AFM) analysis indicated that the annealing temperature had significant effects on surface roughness. By using Fourier transform infrared spectroscopy (FTIR), the resistance to the interface growth after the additional thermal budgets was observed. The thickness and pseudodielectric constants of ZrO2 thin films correlating to annealing temperature were determined by Tauc–Lorentz spectroscopic ellipsometry (SE) dispersion model fitting. Optical band gaps (Eg) were also obtained based on the extracted absorption edge.

Integration of micro-supercapacitors with triboelectric nanogenerators for a flexible self-charging power unit

The rapid development of portable and wearable electronic devices has increased demand for flexible and efficient energy harvesting and storage units. Conventionally, these are built and used separately as discrete components. Herein, we propose a simple and cost-effective laser engraving technique for fabricating a flexible self-charging micro-supercapacitor power unit (SCMPU), by integrating a triboelectric nanogenerator (TENG) and a micro-supercapacitor (MSC) array into a single device. The SCMPU can be charged directly by ambient mechanical motion. We demonstrate the ability of the SCMPU to continuously power light-emitting diodes and a commercial hygrothermograph. This investigation may promote the development of sustainable self-powered systems and provide a promising new research application for supercapacitors.

Bimetallic nano-mushrooms with DNA-mediated interior nanogaps for high-efficiency SERS signal amplification

Uniform silver-containing metal nanostructures with well-defined nanogaps hold great promise for ultrasensitive surface-enhanced Raman scattering (SERS) analyses. Nevertheless, the direct synthesis of such nanostructures with strong and stable SERS signals remains extremely challenging. Here, we report a DNA-mediated approach for the direct synthesis of gold-silver nano-mushrooms with interior nanogaps. The SERS intensities of these nano-mushrooms were critically dependent on the area of the nanogap between the gold head and the silver cap. We found that the formation of nanogaps was finely tunable by controlling the surface density of 6-carboxy-X-rhodamine (ROX) labeled single-stranded DNA (ssDNA) on the gold nanoparticles. We obtained nano-mushrooms in high yield with a high SERS signal enhancement factor of ∼1.0 × 109, much higher than that for Au-Ag nanostructures without nanogaps. Measurements for single nanomushrooms show that these structures have both sensitive and reproducible SERS signals.

Large-Area All-Textile Pressure Sensors for Monitoring Human Motion and Physiological Signals

Wearable pressure sensors, which can perceive and respond to environmental stimuli, are essential components of smart textiles. Here, large-area all-textile-based pressure-sensor arrays are successfully realized on common fabric substrates. The textile sensor unit achieves high sensitivity (14.4 kPa-1 ), low detection limit (2 Pa), fast response (≈24 ms), low power consumption (<6 µW), and mechanical stability under harsh deformations. Thanks to these merits, the textile sensor is demonstrated to be able to recognize finger movement, hand gestures, acoustic vibrations, and real-time pulse wave. Furthermore, large-area sensor arrays are successfully fabricated on one textile substrate to spatially map tactile stimuli and can be directly incorporated into a fabric garment for stylish designs without sacrifice of comfort, suggesting great potential in smart textiles or wearable electronics.

Highly Efficient Storage of Pulse Energy Produced by Triboelectric Nanogenerator in Li3V2(PO4)3/C Cathode Li-Ion Batteries

Triboelectric nanogenerator (TENG) has been considered as a new type of energy harvesting technology, which employs the coupling effects of triboelectrification and electrostatic induction. One key factor having limited its application is the energy storage. In this work, a high performance Li3V2(PO4)3/C material synthesized by low-cost hydrothermal method followed with subsequent annealing treatment was studied to efficiently store the power generated by a radial-arrayed rotary TENG. Not only does the Li3V2(PO4)3/C exhibit a discharge capacity of 128 mAh g(-1) at 1 C with excellent cyclic stability (capacity retention is 90% after 1000 cycles at a rate of 5 C) in Li-ion battery, but also shows outstanding energy conversion efficiency (83.4%) compared with the most popular cathodic materials: LiFePO4 (74.4%), LiCoO2 (66.1%), and LiMn2O4 (73.6%) when it was charged by high frequency and large current electricity directly from by TENG.

Dark-field microscopy in imaging of plasmon resonant nanoparticles.

Dark-field microscopy (DFM) and spectroscopy base on localized surface plasmon resonance (LSPR) have been widely applied in biological sensing and single-molecule imaging. Using plasmonic nanoparticles with controlled geometrical, optical, and surface chemical properties as the probes, the scattering light depending on the surrounding environment can be detected by DF microscope. Signal-to-noise radio and time resolution of the conventional DFM is not sufficient to identify single molecular dynamics. To break these limitations, significant improvements have been made in recent years. This critical review is focused on the developments of the DFM and the utilization of DFM as a powerful technology in the application of LSPR detection.

Real-time visualization of clustering and intracellular transport of gold nanoparticles by correlative imaging

Mechanistic understanding of the endocytosis and intracellular trafficking of nanoparticles is essential for designing smart theranostic carriers. Physico-chemical properties, including size, clustering and surface chemistry of nanoparticles regulate their cellular uptake and transport. Significantly, even single nanoparticles could cluster intracellularly, yet their clustering state and subsequent trafficking are not well understood. Here, we used DNA-decorated gold (fPlas-gold) nanoparticles as a dually emissive fluorescent and plasmonic probe to examine their clustering states and intracellular transport. Evidence from correlative fluorescence and plasmonic imaging shows that endocytosis of fPlas-gold follows multiple pathways. In the early stages of endocytosis, fPlas-gold nanoparticles appear mostly as single particles and they cluster during the vesicular transport and maturation. The speed of encapsulated fPlas-gold transport was critically dependent on the size of clusters but not on the types of organelle such as endosomes and lysosomes. Our results provide key strategies for engineering theranostic nanocarriers for efficient health management.

Core–Shell-Yarn-Based Triboelectric Nanogenerator Textiles as Power Cloths

Although textile-based triboelectric nanogenerators (TENGs) are highly promising because they scavenge energy from their working environment to sustainably power wearable/mobile electronics, the challenge of simultaneously possessing the qualities of cloth remains. In this work, we propose a strategy for TENG textiles as power cloths in which core-shell yarns with core conductive fibers as the electrode and artificial polymer fibers or natural fibrous materials tightly twined around core conductive fibers are applied as the building blocks. The resulting TENG textiles are comfortable, flexible, and fashionable, and their production processes are compatible with industrial, large-scale textile manufacturing. More importantly, the comfortable TENG textiles demonstrate excellent washability and tailorability and can be fully applied in further garment processing. TENG textiles worn under the arm or foot have also been demonstrated to scavenge various types of energy from human motion, such as patting, walking, and running. All of these merits of proposed TENG textiles for clothing uses suggest their great potentials for viable applications in wearable electronics or smart textiles in the near future.