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CK
Verified CAS / Academic Author8 Decoded Studies

Prof. CHEN Kai

College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics

Research Publications & English Decoded Briefs

Showing 8 publications
Surface Technology (表面技术)2026DOI: 10.16490/j.cnki.issn.1001-3660.2026.09.004

A Material Removal Model for KDP Crystal in Chemical Mechanical Polishing Based on Solid-phase Chemical Reactions

Potassium dihydrogen phosphate (KH2PO4, KDP) crystals are indispensable optical components in high-power laser systems and inertial confinement fusion devices, yet their hygroscopicity, brittleness, and low hardness render them among the most difficult materials to machine. This study establishes a solid-phase chemical reaction rate model grounded in heterogeneous solid-phase reaction kinetics and the Arrhenius equation, quantifying the influence of mechanical action and temperature on reaction kinetics. The true contact area between the KDP crystal and the fixed abrasive pad is computed, and the reaction layer thickness is derived by coupling the reaction rate model with single-abrasive scratching theory. A material removal model is subsequently formulated, linking abrasive penetration depth to reaction layer thickness. Experiments were conducted at polishing pressures of 7.5, 15, 22.5, and 30 kPa and pad rotational speeds of 40, 50, 60, 70, and 80 r/min. Theoretical material removal rates were compared with empirical data, yielding discrepancies within 13% (maximum errors of 10.6% at 7.5 kPa and 12.5% at 30 kPa). Material removal rate increases monotonically with polishing pressure and pad rotational speed. The model elucidates the coupling mechanism between chemical and mechanical actions: solid-phase reactions generate a reaction layer on the workpiece surface, which is removed by abrasive mechanical action; equilibrium between chemical and mechanical actions enables high-quality KDP crystal processing.

Nano-Micro Letters2025DOI: 10.1007/s40820-025-01798-x

A Strongly Coupled Cluster Heterostructure with Pt–N–Mo Bonding for Durable and Efficient H2 Evolution in Anion-Exchange Membrane Water Electrolyzers

Creating strongly coupled heterostructures with favorable catalytic activities is crucial for promoting the performance of catalytic reactions, especially those involve multiple intermediates. Herein, we fabricated a strongly coupled platinum/molybdenum nitrides nanocluster heterostructure on nitrogen-doped reduced graphene oxide (Pt/Mo₂N–NrGO) for alkaline hydrogen evolution reaction. The well-defined Pt-containing Anderson-type polyoxometalates promote strong interfacial Pt–N–Mo bonding in Pt/Mo2N–NrGO, which exhibits a remarkably low overpotential, high mass activity, and exceptional long-term durability (> 500 h at 1500 mA cm⁻2) in an anion-exchange membrane water electrolyzer (AEMWE). Operando Raman spectroscopy and density functional theory reveal that pronounced electronic coupling at the Pt/Mo₂N cluster interface facilitates the catalytic decomposition of H2O through synergistic stabilization of intermediates (Pt–H* and Mo-OH*), thereby enhancing the kinetics of the rate-determining Volmer step. Techno-economic analysis indicates a levelized hydrogen production cost of $2.02 kg⁻1, meeting the US DOE targets. Our strategy presents a viable pathway to designing next-generation catalysts for industrial AEMWE for green hydrogen production.

Nano-Micro Letters2025DOI: 10.1007/s40820-025-01704-5

Water-Restrained Hydrogel Electrolytes with Repulsion-Driven Cationic Express Pathways for Durable Zinc-Ion Batteries

The development of flexible zinc-ion batteries (ZIBs) faces a three-way trade-off among the ionic conductivity, Zn2+ mobility, and the electrochemical stability of hydrogel electrolytes. To address this challenge, we designed a cationic hydrogel named PAPTMA to holistically improve the reversibility of ZIBs. The long cationic branch chains in the polymeric matrix construct express pathways for rapid Zn2+ transport through an ionic repulsion mechanism, achieving simultaneously high Zn2+ transference number (0.79) and high ionic conductivity (28.7 mS cm−1). Additionally, the reactivity of water in the PAPTMA hydrogels is significantly inhibited, thus possessing a strong resistance to parasitic reactions. Mechanical characterization further reveals the superior tensile and adhesion strength of PAPTMA. Leveraging these properties, symmetric batteries employing PAPTMA hydrogel deliver exceeding 6000 h of reversible cycling at 1 mA cm−2 and maintain stable operation for 1000 h with a discharge of depth of 71%. When applied in 4 × 4 cm2 pouch cells with MnO2 as the cathode material, the device demonstrates remarkable operational stability and mechanical robustness through 150 cycles. This work presents an eclectic strategy for designing advanced hydrogels that combine high ionic conductivity, enhanced Zn2+ mobility, and strong resistance to parasitic reactions, paving the way for long-lasting flexible ZIBs.

Nano-Micro Letters2025DOI: 10.1007/s40820-025-01662-y

Microneedle-Based Approaches for Skin Disease Treatment

The use of microneedles (MNs) has been established as an effective transdermal drug delivery strategy that has been extensively deployed for treating various diseases, including skin diseases. MNs can surpass the constraints of conventional drug delivery methods by their superior safety and efficacy through precise targeting, while simultaneously enabling painless delivery. Currently, MNs are increasingly used as carriers for drug delivery, with the loading of insoluble drugs to improve their treatment efficiency or combining with bioactive substances for the construction of an efficient drug delivery system to maximize the effects of bioactive substances. The methods used for preparation MNs are diverse, enabling them to meet the requirements of most applications. The emergence of MNs has addressed the shortcomings associated with insoluble drugs, expanded the applications of bioactive substances, and improved their use in clinical practice. This review summarizes current information on the application of MNs in a variety of skin diseases, such as psoriasis, vitiligo, alopecia, hypertrophic scarring, atopic dermatitis, melanoma, acne, and skin infections. The current clinical applications and future opportunities for MNs in the treatment of skin diseases are also discussed. Despite substantial progress in the clinical application of MNs as delivery vectors, issues such as low drug loading and poor mechanical strength during MNs preparation remain the main challenges. Therefore, clinical implementation of MNs-based therapies remains limited, highlighting key opportunities for future research.

Nano-Micro Letters2025DOI: 10.1007/s40820-025-01652-0

Novel Cellulosic Fiber Composites with Integrated Multi-Band Electromagnetic Interference Shielding and Energy Storage Functionalities

In an era where technological advancement and sustainability converge, developing renewable materials with multifunctional integration is increasingly in demand. This study filled a crucial gap by integrating energy storage, multi-band electromagnetic interference (EMI) shielding, and structural design into bio-based materials. Specifically, conductive polymer layers were formed within the 2,2,6,6-tetramethylpiperidine-1-oxide (TEMPO)-oxidized cellulose fiber skeleton, where a mild TEMPO-mediated oxidation system was applied to endow it with abundant macropores that could be utilized as active sites (specific surface area of 105.6 m2 g−1). Benefiting from the special hierarchical porous structure of the material, the constructed cellulose fiber-derived composites can realize high areal-specific capacitance of 12.44 F cm−2 at 5 mA cm−2 and areal energy density of 3.99 mWh cm−2 (2005 mW cm−2) with an excellent stability of maintaining 90.23% after 10,000 cycles at 50 mA cm−2. Meanwhile, the composites showed a high electrical conductivity of 877.19 S m−1 and excellent EMI efficiency (>99.99%) in multiple wavelength bands. The composite material’s EMI values exceed 100 dB across the L, S, C, and X bands, effectively shielding electromagnetic waves in daily life. The proposed strategy paves the way for utilizing bio-based materials in applications like energy storage and EMI shielding, contributing to a more sustainable future.

Chinese Journal of Mechanical Engineering2025DOI: 10.1186/s10033-025-01356-x

A Comprehensive Review of Key Technologies for Robot Motion Planning in Contact Tasks in Industrial Automation Scenarios

With the swift advancement of industrial automation, robots have emerged as an essential component in emerging industries and high-end equipment, thereby propelling industrial production towards greater intelligence and efficiency. This paper reviews the pivotal technologies for motion planning of robots engaged in contact tasks within industrial automation contexts, encompassing environmental recognition, trajectory generation strategies, and sim-to-real transfer. Environmental recognition technology empowers robots to accurately discern objects and obstacles in their operational environment. Trajectory generation strategies formulate optimal motion paths based on environmental data and task specifications. Sim-to-real transfer is committed to effectively translating strategies from simulated environments to actual production, thereby diminishing the discrepancies between simulation and reality. The article also delves into the application of artificial intelligence in robot motion planning and how embodied intelligence models catalyze the evolution of robotics technology towards enhanced intelligence and automation. The paper concludes with a synthesis of the methodologies addressing this challenge and a perspective on the myriad challenges that warrant attention.

Nano-Micro Letters2025DOI: 10.1007/s40820-024-01564-5

Ligand Engineering Achieves Suppression of Temperature Quenching in Pure Green Perovskite Nanocrystals for Efficient and Thermostable Electroluminescence

Formamidinium lead bromide (FAPbBr3) perovskite nanocrystals (NCs) are promising for display and lighting due to their ultra-pure green emission. However, the thermal quenching will exacerbate their performance degradation in practical applications, which is a common issue for halide perovskites. Here, we reported the heat-resistant FAPbBr3 NCs prepared by a ligand-engineered room-temperature synthesis strategy. An aromatic amine, specifically β-phenylethylamine (PEA) or 3-fluorophenylethylamine (3-F-PEA), was incorporated as the short-chain ligand to expedite the crystallization rate and control the size distribution of FAPbBr3 NCs. Employing this ligand engineering approach, we synthesized high quality FAPbBr3 NCs with uniform grain size and reduced long-chain alkyl ligands, resulting in substantially suppressed thermal quenching and enhanced carrier transportation in the perovskite NCs films. Most notably, more than 90% of the room temperature PL intensity in the 3-F-PEA modified FAPbBr3 NCs film was preserved at 380 K. Consequently, we fabricated ultra-pure green EL devices with a room temperature external quantum efficiency (EQE) as high as 21.9% at the luminance of above 1,000 cd m−2, and demonstrated less than 10% loss in EQE at 343 K. This study introduces a novel room temperature method to synthesize efficient FAPbBr3 NCs with exceptional thermal stability, paving the way for advanced optoelectronic device applications.

Nano-Micro Letters2025DOI: 10.1007/s40820-024-01512-3

Gradient-Layered MXene/Hollow Lignin Nanospheres Architecture Design for Flexible and Stretchable Supercapacitors

With the rapid development of flexible wearable electronics, the demand for stretchable energy storage devices has surged. In this work, a novel gradient-layered architecture was design based on single-pore hollow lignin nanospheres (HLNPs)-intercalated two-dimensional transition metal carbide (Ti3C2Tx MXene) for fabricating highly stretchable and durable supercapacitors. By depositing and inserting HLNPs in the MXene layers with a bottom-up decreasing gradient, a multilayered porous MXene structure with smooth ion channels was constructed by reducing the overstacking of MXene lamella. Moreover, the micro-chamber architecture of thin-walled lignin nanospheres effectively extended the contact area between lignin and MXene to improve ion and electron accessibility, thus better utilizing the pseudocapacitive property of lignin. All these strategies effectively enhanced the capacitive performance of the electrodes. In addition, HLNPs, which acted as a protective phase for MXene layer, enhanced mechanical properties of the wrinkled stretchable electrodes by releasing stress through slip and deformation during the stretch-release cycling and greatly improved the structural integrity and capacitive stability of the electrodes. Flexible electrodes and symmetric flexible all-solid-state supercapacitors capable of enduring 600% uniaxial tensile strain were developed with high specific capacitances of 1273 mF cm−2 (241 F g−1) and 514 mF cm−2 (95 F g−1), respectively. Moreover, their capacitances were well preserved after 1000 times of 600% stretch-release cycling. This study showcased new possibilities of incorporating biobased lignin nanospheres in energy storage devices to fabricate stretchable devices leveraging synergies among various two-dimensional nanomaterials.