Publications

We demonstrate a new flexible multilayered triboelectric nanogenerator (TENG) with extremely low cost, simple structure, small size (3.8 cm×3.8 cm×0.95 cm) and lightweight (7 g) by innovatively integrating five layers of units on a single flexible substrate. Owing to the unique structure and nanopore-based surface modification on the metal surface, the instantaneous short-circuit current (Isc) and the open-circuit voltage (Voc) could reach 0.66 mA and 215 V with an instantaneous maximum power density of 9.8 mW/cm2 and 10.24 mW/cm3. This is the first 3D integrated TENG for enhancing the output power. Triggered by press from normal walking, the TENG attached onto a shoe pad was able to instantaneously drive multiple commercial LED bulbs. With the flexible structure, the TENG can be further integrated into clothes or even attached onto human body without introducing sensible obstruction and discomfort to human motions. The novel design of TENG demonstrated here can be applied to potentially achieve self-powered portable electronics.

We report high-performance self-aligned MoS2 field-effect transistors (FETs) with enhanced photoresponsivity by the piezo-phototronic effect. The FETs are fabricated based on monolayer MoS2 with a piezoelectric GaN nanowire (NW) as the local gate, and a self-aligned process is employed to define the source/drain electrodes. The fabrication method allows the preservation of the intrinsic property of MoS2 and suppresses the scattering center density in the MoS2/GaN interface, which results in high electrical and photoelectric performances. MoS2 FETs with channel lengths of ∼200 nm have been fabricated with a small subthreshold slope of 64 mV/dec. The photoresponsivity is 443.3 A·W–1, with a fast response and recovery time of ∼5 ms under 550 nm light illumination. When strain is introduced into the GaN NW, the photoresponsivity is further enhanced to 734.5 A·W–1 and maintains consistent response and recovery time, which is comparable with that of the mechanical exfoliation of MoS2 transistors. The approach presented here opens an avenue to high-performance top-gated piezo-enhanced MoS2 photodetectors.

Abstract Although triboelectric nanogenerators (TENGs) are highly efficient and adaptable in harvesting ocean wave energy, the dynamics of floating TENGs in underwater wave stimulations have so far rarely been studied. Herein, the interactions between centimeter‐scaled floating structures and water waves are experimentally revealed. By integrating inertial measurement units into the shells of various floating TENG structures, the primary acceleration data associated with different parameters are obtained. Based on the data of 63 literature reported floating TENGs, a series of experimental parameters are elaborately probed, including shell shape, shell size, weight, barycenter, wave strength/frequency, and wave‐producing methods. Through dynamic calculations, each can offer the kernel data of acceleration and frequency distribution curves, revealing several regularities in water–structure interactions associated with TENGs. These calculations could serve as guidance for the design of the future floating TENGs in blue energy harvesting.

Abstract With increasing global warming, catastrophic floods have threatened people's lives seriously and caused huge economic losses. However, present water hazard alarming systems generally rely on commercial batteries, limiting the intelligent development of disaster prevention planning and maintenance costs. In order to break the limitation, this work applies triboelectric nanogenerators (TENGs) to water hazard alarming. A spherical TENG device with four spiral units is designed to harvest water wave energy, and charge excitation modules (CEMs) are created and integrated with the TENG to improve its electric output. The output current and output power of the spherical TENG with CEMs can reach 15.09 mA and 24.48 mW, which are increased by 250.5 and 4.0 times, compared to the TENG without CEMs. Based on the charge excitation TENG, a self‐powered intelligent buoy is constructed. Utilizing the buoy to transmit 433 MHz radio frequency signals to 25 meters away, a water level alarm system and a water level information exchange system with a mobile phone are successfully realized. This work extends applications of TENGs toward water wave energy harvesting and provides a new strategy for water hazard alarming, which is conducive to the fields of carbon neutralization, Internet of Things, and disaster prevention.

Abstract Rapid progress in nanotechnology allows us to develop a large number of innovative wearables such as activity trackers, advanced textiles, and healthcare devices. However, manufacturing processes for desirable nanostructure are usually complex and expensive. Moreover, materials used for these devices are mainly derived from nonrenewable resources. Therefore, it poses growing problems for living environment, and causes incompatible discomfort for human beings with long‐time wearing. Here, a self‐powered cellulose fiber based triboelectric nanogenerator (cf‐TENG) system is presented through developing 1D eco‐friendly cellulose microfibers/nanofibers (CMFs/CNFs) into 2D CMFs/CNFs/Ag hierarchical nanostructure. Silver nanofibers membrane is successfully introduced into the cf‐TENG system by using CMFs/CNFs as template, which shows excellent antibacterial activity. Enabled by its desirable porous nanostructure and unique electricity generation feature, the cf‐TENG system is capable of removing PM 2.5 with high efficiency of 98.83% and monitoring breathing status without using an external power supply. This work provides a novel and sustainable strategy for self‐powered wearable electronics in healthcare applications, and furthermore paves a way for next‐generation flexible, biocompatible electronics.

Current multimodal large language models (MLLMs) struggle with fine-grained or precise understanding of visuals though they give comprehensive perception and reasoning in a spectrum of vision applications. Recent studies either develop tool-using or unify specific visual tasks into the autoregressive framework, often at the expense of overall multimodal performance. To address this issue and enhance MLLMs with visual tasks in a scalable fashion, we propose Task Preference Optimization (TPO), a novel method that utilizes differentiable task preferences derived from typical fine-grained visual tasks. TPO introduces learnable task tokens that establish connections between multiple task-specific heads and the MLLM. By leveraging rich visual labels during training, TPO significantly enhances the MLLM's multimodal capabilities and task-specific performance. Through multi-task co-training within TPO, we observe synergistic benefits that elevate individual task performance beyond what is achievable through single-task training methodologies. Our instantiation of this approach with VideoChat and LLaVA demonstrates an overall 14.6% improvement in multimodal performance compared to baseline models. Additionally, MLLM-TPO demonstrates robust zero-shot capabilities across various tasks, performing comparably to state-of-the-art supervised models. The code will be released at https://github.com/OpenGVLab/TPO

We have previously shown that high-purity multiwalled carbon nanotubes (pristine MWNTs) can be prepared from a mixture of xylene-ferrocene (99 at% C:1 at% Fe) inside a quartz tube reactor operating at approximately 700 degrees C. In a similar process, approximately 3 g of melamine (C3H6N6) was introduced during the growth of MWNTs to prepare nitrogen-doped nanotubes. The structural and electronic properties of nitrogen-doped MWNTs were determined by scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and thermopower measurements. The individual nitrogen-doped nanotube exhibits a bamboo-like structure and comprises 6-16 tube walls, as evidenced by HRTEM studies. The EELS measurements yielded an average nitrogen content of approximately 5 at% in the doped tubes. The thermoelectric power data of nitrogen-doped MWNTs remained negative even after exposure to oxygen for an extended period of time, suggesting that nitrogen doping of MWNTs renders them n-type, consistent with scanning tunneling spectroscopic studies on similar nanotubes.

By converting ambient energy into electricity, energy harvesting is capable of at least offsetting, or even replacing, the reliance of small portable electronics on traditional power supplies, such as batteries. Here we demonstrate a novel and simple generator with extremely low cost for efficiently harvesting mechanical energy that is typically present in the form of vibrations and random displacements/deformation. Owing to the coupling of contact charging and electrostatic induction, electric generation was achieved with a cycled process of contact and separation between two polymer films. A detailed theory is developed for understanding the proposed mechanism. The instantaneous electric power density reached as high as 31.2 mW/cm(3) at a maximum open circuit voltage of 110 V. Furthermore, the generator was successfully used without electric storage as a direct power source for pulse electrodeposition (PED) of micro/nanocrystalline silver structure. The cathodic current efficiency reached up to 86.6%. Not only does this work present a new type of generator that is featured by simple fabrication, large electric output, excellent robustness, and extremely low cost, but also extends the application of energy-harvesting technology to the field of electrochemistry with further utilizations including, but not limited to, pollutant degradation, corrosion protection, and water splitting.

Recycling of residual biomass in the form of carbonaceous materials is a sustainable and economically viable management option with zero net carbon dioxide emissions. Mesoporous bamboo biochars were produced via microwave-assisted hydrothermal/soft template treatment. Then they were characterized and evaluated for their adsorption capabilities for three organics. The biochars were found to have mesoporous structures with BET surface areas of 13.0 to 288 m2/g, total pore volumes in the range of 0.017 to 0.313 cm3/g, and average pore diameters between 4.0 and 6.7 nm in size. The surface areas and pore volumes were highly related to the hydrothermal treatment conditions. The mesoporous bamboo biochars showed adsorption amounts for 2-naphthol, berberine hydrocholoride, and Congo red in the range of 35.0 to 155.7, 76.1 to 129.6, 57.9 to 114.4 mg/g, respectively, at the adsorbate concentration of 0.5 mg/mL, and their adsorption capabilities depended on both the porosity and the surface groups. The adsorption of the three organics on the selected sample was a spontaneous and exothermic process with physical adsorption as the dominant mechanism. The adsorption could achieve equilibrium within 20, 40, and 60 min for 2-naphthol, berberine hydrochloride, and Congo red, respectively. This study provides a prospective method to produce biomass-derived mesoporous carbon adsorbents for adsorptive separation of organics from water.

Single‐electrode triboelectric nanogenerators (SETENGs) significantly expand the application of triboelectric nanogenerators in various circumstances, such as touch‐pad technologies. In this work, a theoretical model of SETENGs is presented with in‐depth interpretation and analysis of their working principle. Electrostatic shield effect from the primary electrode is the main consideration in the design of such SETENGs. On the basis of this analysis, the impacts of two important structural parameters, that is, the electrode gap distance and the area size, on the output performance are theoretically investigated. An optimized electrode gap distance and an optimized area size are observed to provide a maximum transit output power. Parallel connection of multiple SETENGs with micro‐scale size and relatively larger spacing should be utilized as the scaling‐up strategy. The discussion of the basic working principle and the influence of structural parameters on the whole performance of the device can serve as an important guidance for rational design of the device structure towards the optimum output in specific applications.

'Photolithography' published in 'Encyclopedia of Nanotechnology'