GZ

G.Q. Zhang

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569 records found

Journal article (2026) - Chenshan Gao, L. Du, Tianxing Du, Qihang Zong, Shizhen Li, Huiru Yang, G.Q. Zhang, H. Ye
Sintered porous Cu contains a heterogeneous particle-neck-pore architecture whose deformation depends strongly on loading mode. In this study, porous Cu structures prepared from small particles (184 nm) and large particles (1451 nm) were examined using micropillar compression, micro-cantilever bending, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and molecular dynamics (MD) simulations. Under compression, the large-particle structure exhibited a higher apparent elastic modulus (14.5 ± 0.9 GPa) than the small-particle structure (12.7 ± 0.5 GPa), whereas the small-particle structure showed an approximately 80% higher yield strength (364 ± 58 versus 202 ± 71 MPa). In contrast, the large-particle structure exhibited an approximately 245% higher conditional fracture toughness (5.56 ± 0.14 versus 1.61 ± 0.16 MPa⋅m1/2) and 1270% higher total bending work (8823 ± 1245 versus 644 ± 164 pJ). Microstructural analyses revealed that the refined particle-neck network accommodated compression through distributed pore compaction, neck deformation, and dislocation accumulation, suppressing strain localization. The coarser network promoted intraparticle slip and interfacial sliding under compression, while enhancing remaining-ligament continuity and neck bridging during crack propagation. MD simulations reproduced these distinct compressive responses and defect-evolution characteristics. These findings provide guidance for optimizing particle-neck-pore architectures in reliable sintered Cu interconnects. ...
Journal article (2026) - Leo Guo, Hirak Kansara, Siamak F. Khosroshahi, Guo Qi Zhang, Wei Tan
Finite element (FE) simulations of structures and materials are becoming increasingly accurate, but also more computationally expensive as a collateral result. This development occurs in parallel with a growing demand for data-driven design. To reconcile the two, a robust and data-efficient optimization method called Bayesian optimization (BO) has been previously established as a technique to optimize expensive objective functions. The mesh width of an FE model can be exploited to evaluate an objective at a lower or higher fidelity (cost & accuracy) level, which is the domain of multi-fidelity BO (MFBO) applications. However, BO and MFBO are usually not directly compared in the literature. Moreover, sampling quality and assessing design parameter sensitivity are often underrepresented parts of data-driven design. This paper combines global sensitivity analysis and (MF) BO into a novel, efficient Bayesian data-driven framework. We compare the performance of BO with that of MFBO by maximizing the energy absorption (EA) problem of spinodoid cellular structures. The findings show that similar or better designs are suggested by MFBO with 16% fewer expensive objective evaluations compared to BO when maximizing the EA. The results, which are made open-source, serve to support the utility of multi-fidelity techniques across expensive data-driven design problems. ...
Journal article (2026) - Jingya Tang, Chenyang Yang, Jianwen Sun, Zhe Li, Yue Men, Zewen Liu, Guoqi Zhang, Xian En Zhang, Dian Bing Wang
Ultrasensitive and specific detection of low-abundance tumor biomarkers remains a major challenge for early and minimally invasive cancer diagnosis. Here, we present a high-performance biosensing platform that integrates a genetically engineered bacterial S-layer with an AlGaN/GaN high-electron-mobility transistor (HEMT) sensor for label-free detection of tumor antigens. As a proof-of-concept, the ovarian cancer antigen human epididymis protein 4 (HE4) was selected . Specifically, the S-layer protein rSbpA was fused with HE4-specific nanobody 1G8 to construct a bifunctional membrane capable of self-assembling into an ordered biorecognition layer on the sensor surface. Compared to conventional chemical crosslinking, S-layer-driven assembly increased antibody loading by 50 % and minimized nonspecific adsorption in plasma environments. The resulting HEMT sensor detected HE4 across a dynamic linear range (10−21 to 10−14 M), identifying patients with ovarian cancer with 100 % diagnostic accuracy (AUC = 1.0). This study establishes a versatile and modular biosensing strategy for ultra-low-abundance biomarker detection with broad potential applications in the precision diagnostics of cancer and other diseases. ...
Conference paper (2026) - Shizhen Li, Chenshan Gao, Xu Liu, Huaiyu Ye, Guoqi Zhang
The semiconductor industry is facing significant challenges, including physical limitations such as heat dissipation, rising manufacturing costs, and the difficulty of further shrinking transistor sizes while maintaining performance. To address these issues, chiplet technology has emerged, integrating smaller, specialized chips into a single package. This approach improves modularity, manufacturing yields, and allows mixing different technology nodes for optimal performance. However, challenges like ensuring high-speed, low-latency interconnects and effective thermal management persist.This study explores several key aspects of chiplet technology using a simplified dual-chip model, focusing on the integration of nanocopper materials. By comparing nanocopper with traditional solder, we analyze differences in mechanical behavior and thermal management. Additionally, we investigate variations in chiplet layout, examining the impact of spacing and the number of chiplets on performance under identical power conditions. Our findings indicate that nanocopper interconnects provide lower stress and better thermal conductivity than traditional solder. Adjusting chiplet spacing and increasing the number of chiplets both enhance heat dissipation. Future work will involve larger-scale simulations and fatigue analyses to optimize chiplet packaging for improved performance and reliability. ...
Journal article (2026) - Hongyu Tang, Ninghai Yu, Pengsheng Min, Ruiqian Guo, Guoqi Zhang
In-sensor-memory computing (ISMC) resolves von Neumann bottlenecks via synergistic innovations across multi-dimensional functional materials, hybrid architectures, and algorithm-hardware co-design. This paradigm empowers ultra-low-latency edge applications, paving the way for autonomous systems, bio-integrated healthcare, and decentralized swarm intelligence. Translating ISMC into scalable commercialization necessitates global Industry-Academia-Research collaboration, application-centric benchmarking protocols, and cross-disciplinary ecosystem enablers. ...
Conference paper (2026) - Shaojian Xie, Mesfin Seid Ibrahim, Jialong Liang, Hiu Hung Lee, Chang Lu, Guoqi Zhang, Jiajie Fan
Aiming at the reliability bottlenecks of power MOSFETs in such key application fields as new energy vehicles (NEVs), photovoltaic (PV) inverters, and industrial motor drives, this paper proposes an unsupervised anomaly detection method for power MOSFET degradation based on the Long Short-Term Memory Autoencoder (LSTM-AE). Without relying on labeled data or complex hardware modifications, the method can adaptively learn the health patterns and temporal features of devices, addressing the limitations of traditional methods such as difficulty in capturing long-term dependencies and poor noise immunity. Three different test conditions for power cycling tests were designed to collect operational data of power MOSFET devices. On-state resistance (RDS(on)) and body diode voltage drop(VSD) were selected as input features, and the Leave-One-Out Cross-Validation (LOOCV) method was adopted to verify the model performance. Experimental results demonstrate that the method can effectively capture weak degradation features during the stage of insignificant device performance changes, achieving an early warning prior to device failure. Under 3σ principle threshold, its detection performance outperforms the Multilayer Perceptron Autoencoder (MLP-AE) and traditional Mahalanobis Distance (MD) methods, with the optimal sequence size being 64. It achieves a high accuracy in identifying normal states and exhibits high recognition capability for severely degraded states, providing a robust, efficient, and practical solution for the health monitoring of power MOSFETs. ...
Conference paper (2026) - A.N.M.K. Abdelwahab, Z. Farmani, H. Kuipers, M. Tichem, J. Fan, Kouchi Zhang
Handling ultra-thin semiconductor dies during assembly remains challenging due to their mechanical fragility and sensitivity to placement forces. Contactless die transfer methods reduce mechanical loading and have potential to enable higher placement speeds and improved throughput but introduce challenges such as uncontrolled impact dynamics, die rebound, and misalignment during landing. This work investigates a liquid-assisted contactless adhesive bonding approach in which droplets deposited on stencil-printed conductive adhesive act as transient damping and alignment media during die landing. Dummy silicon dies with a gold (Au) surface finish were released from a short distance onto the adhesive. Four liquids with different physical and chemical properties—deionized (DI) water, isopropyl alcohol (IPA), acetone, and liquid flux—were investigated to evaluate the influence of key fluid parameters, including surface tension, viscosity, and density, on die impact dynamics, stabilization, and subsequent bonding quality. The results demonstrate that droplet material properties significantly influence die landing dynamics in liquid-assisted contactless assembly. Among the investigated liquids, deionized water enabled reliable die entrapment and damping. In contrast, for the lower-surface-tension solvents isopropyl alcohol (IPA) and acetone, the droplets were not sufficiently confined under the experimental conditions, and therefore no direct die entrapment was observed, although impact damping was still achieved. Die entrapment and stabilization behavior were analyzed using high-speed camera recordings and complementary two-dimensional simulations performed in COMSOL Multiphysics. Furthermore, the impact of the droplets on the resulting bond interface and joint quality was evaluated through post-bond characterization. The study provides insight into droplet-mediated die landing and offers guidelines for selecting liquids for reliable contactless micro-assembly. ...

Mechanisms, Strategies, and Industrial Perspectives

Review (2026) - Mingliang Zhang, Ruiyang Xiao, Hanqing Dai, Wanlu Zhang, Guoqi Zhang, Ruiqian Guo
Sustainable hydrogen production via water electrolysis is pivotal to addressing global energy and environmental challenges. Among emerging materials, quantum dots (QDs) have garnered significant attention for the hydrogen evolution reaction (HER) due to their zero-dimensional nanostructure, high specific surface area, tunable electronic characteristics, and abundant active sites. This review provides a comprehensive overview of recent advancements in QD-based catalysts for electrocatalytic HER, focusing on the fundamental mechanisms that drive their enhanced performance. Key enhancement strategies—such as substrate dispersion, surface functionalization, defect engineering, and heteroatom doping—are critically discussed. Furthermore, the review explores the potential of QD-based catalysts for large-scale and industrial applications. By synthesizing current progress and challenges, this review offers critical insights into the rational design of next-generation HER catalysts to advance sustainable hydrogen energy. ...
Journal article (2026) - Jiajie Fan, Xuyang Yan, Chuantong Chen, Leiming Du, Zichuan Li, Junran Zhang, Willem Van Driel, Guoqi Zhang
Sintered Cu nanoparticles (Cu NPs) are promising interconnection materials for high-temperature power electronics, yet how their authentic three-dimensional pore architecture governs microscale deformation remains unclear. Here, synchrotron nano-computed tomography (nano-CT) was combined with in-situ micropillar compression, explicit dynamic elastoplastic finite element analysis, and TEM/TKD characterization to interrogate sintered Cu NPs. The nano-CT voxel size was 45 nm, and the reconstructed volume corresponded to a cylinder 16 µm in diameter and 10 µm in height. The average sectional porosity was 12.44%, with a systematic discrepancy between two-dimensional and three-dimensional porosity quantification. During loading, the porosity decreased to 9.55% while the pore aspect ratio increased from 1.82–2.35. Finite element analysis further showed pronounced pore-adjacent stress/strain localization at the elastic–plastic transition, with local stress and equivalent plastic strain reaching 650 MPa and 1.7 × 10−2, compared with 250 MPa and 1.1 × 10−3 in adjacent regions. The GND density increased by 95.9% at a compressive strain of 26%, linking pore-induced strain gradients to dislocation accumulation. These results quantitatively connect authentic three-dimensional pore architecture, local deformation localization, and dislocation-mediated strengthening in sintered Cu NPs. Highlights Synchrotron nano-CT (45 nm voxel size) reconstructed a 16 × 10 µm cylindrical volume of sintered Cu NPs and resolved the authentic 3D pore network. Sectional porosity was 12.44%, and 2D/3D quantification showed a systematic discrepancy, with porosity decreasing to 9.55% and pore aspect ratio increasing from 1.82 to 2.35 during compression. Pore-adjacent localization was quantified at the elastic–plastic transition, with local stress/PEEQ reaching 650 MPa and 1.7 × 10−2 versus 250 MPa and 1.1 × 10−3 in adjacent regions. A 95.9% increase in GND density at 26% compressive strain links pore-induced strain gradients to dislocation accumulation and strain-gradient-driven strengthening. ...
Journal article (2026) - Tianxing Du, Chenshan Gao, Lai Wei, Huaiyu Ye, Guoqi Zhang, Leiming Du
Sintered copper (Cu) particles are widely used in catalysis, biomedical devices, energy systems and electronic packaging, yet the role of particle morphology in governing their mechanical response remains insufficiently resolved. Here, we investigate porous sintered Cu produced from monomodal spherical, bimodal spherical and flake-shaped particles by combining nanoindentation, scanning electron microscopy (SEM) and molecular dynamics (MD) simulations. Both spherical and Berkovich indenters were used to interrogate morphology-dependent deformation mechanisms. The bimodal spherical network exhibited the highest elastic modulus, whereas the monomodal spherical network showed the highest indentation yield strength. In contrast, the flake-derived network displayed substantially reduced elastic modulus and strength due to weak through-thickness connectivity. Correlative SEM images and MD simulations reveal morphology-dependent deformation mechanisms: distributed neck plasticity in the monomodal network, hierarchical load sharing between coarse and fine particles in the bimodal network, and anisotropic strain localization along interlamellar interfaces in the flake-derived network. Indenter geometry further modulates the response, with spherical indentation promoting distributed compaction and Berkovich indentation promoting stress concentration at weak interfaces. These findings highlight particle morphology as a critical factor governing the topology-dependent mechanical performance of porous sintered Cu. ...
Accurate lifetime prediction of power semiconductor devices is critical for the reliability of power electronic systems. Power cycling tests generate only a small number of failure samples due to their high cost and long duration. This data scarcity makes it difficult to train reliable prediction models. At the same time, modern deep learning models require significant AI expertise to configure and tune, which creates a barrier for reliability engineers. To address these two problems, this paper proposes a domain-constrained multi-agent framework for automated remaining useful life (RUL) prediction of power semiconductor devices. The framework integrates three collaborative agents: a Stats Agent for statistical reliability assessment, a Physics Agent for physical plausibility validation, and a Model Agent for algorithm selection and hyperparameter tuning. A Central Controller manages the workflow and coordinates agent communication. The agents interact through a Propose-Critique-Refine (PCR) mechanism, in which the Model Agent proposes configurations and the other two agents critique them from statistical and physical perspectives. This iterative negotiation eliminates the need for manual parameter tuning. The framework is validated on the NASA IGBT accelerated aging dataset under Leave-One-Device-Out Cross-Validation. Results show that the framework achieves an R2 of 0.914 at a 50% observation ratio and remains above 0.79 even at 30%, demonstrating strong generalization under limited data conditions. ...
Conference paper (2026) - Xiao Hu, Zichuan Li, Chao Gu, Junwei Chen, Jianlin Huang, René Poelma, Jiajie Fan, Willem D. Van Driel, Guoqi Zhang
Porous sintered Ag die-attach layers in power electronics undergo continuous microstructural evolution under high-temperature and high-power-density service conditions. Grain coarsening and pore migration induce stress concentration, thereby critically affecting long-term reliability. However, existing simulation approaches typically capture either microstructure evolution or thermo-mechanical response alone, limiting predictive reliability assessment. This work develops a hybrid Potts-Phase field framework coupled with an FFT-based thermo-mechanical solver to enable bidirectional coupling between microstructure evolution and thermo-mechanical response. Thermal strain arises from the CTE mismatch within the Si/Ag/Cu structure, while grain-orientation-dependent elastic anisotropy is incorporated. Plastic deformation is evaluated using a von Mises yield criterion with Hall-Petch grain-size-dependent strength. The accumulated equivalent plastic strain (PEEQ) is adopted as a physically interpretable damage precursor. The model was validated against cross-sectional EBSD characterization of samples aged at 250 °C for 1008 hours. Predicted stress localization near pores and fine-grained regions agrees with experimentally extracted GND density distributions, and simulated grain coarsening trends match measured grain size evolution. The proposed framework provides a scalable approach for reliability assessment of micro-and nanoscale interconnects under long-term thermal aging. ...
Conference paper (2026) - Y. Wu, H. Wang, Y. Wang, C. Tan, H. Ye, W. Zhang, Kouchi Zhang
The rapid expansion of the electric vehicle industry has accelerated the adoption of Silicon Carbide (SiC) HybridPACK Drive (HPD) power modules to meet the escalating demand for high-efficiency power conversion. However, under high power density conditions, these modules encounter significant reliability challenges stemming from intricate multi-physics interactions across electrical, thermal, and mechanical domains. This study employs multi-physics simulations to systematically evaluate the synergistic effects of several critical design variables—including pin-fin geometry and gradient arrangements, die-attach materials and processes, and chip interconnection structures—on the module’s temperature and current-sharing uniformity. Based on the simulation results, an optimal configuration was identified for sample fabrication and experimental validation. By correlating empirical measurements with simulation data, this research elucidates the configurations that provide superior performance under constant heat flux conditions. The findings establish a robust theoretical and practical framework for enhancing the reliability and operational consistency of SiC HPD power modules through multi-factor comprehensive optimization. ...

Soft biodegradable implants redefine deep-tissue sensing

Journal article (2026) - Liwei Wang, Qianwang Ye, Xinlin Du, Yiwei Xu, Wanlu Zhang, Guoqi Zhang, Ruiqian Guo, Hanqing Dai
Monitoring physiological signals deep inside the body has long been a technological and conceptual challenge. Pressure, temperature, and mechanical strain within organs often precede overt symptoms and guide clinical decision-making, yet they remain difficult to access continuously and noninvasively... ...
Journal article (2026) - Zezhan Li, Wei Du, Xuyang Yan, Chao Gu, Xueliang Wang, Tiancheng Tian, Willem van Driel, Guoqi Zhang, Jiajie Fan
Pressureless sintered Ag pastes are promising die-attach materials for power electronics, yet practical sintering-profile optimization still relies heavily on trial-and-error, and the link from thermal kinetics to fracture-relevant microstructure and strength remains insufficiently established. In this work, a thermal-kinetics-guided workflow was developed to design paste-specific pressureless sintering profiles for two commercial Ag pastes (a spherical-particle paste and a flake-based paste) and to interpret the resulting strength–fracture response using SEM-based, heterogeneity-aware learning. Multi-heating-rate TGA was used to define the conversion fraction (α), while DSC was used to identify the dominant thermal-event window and extract the characteristic peak temperature for Arrhenius pairing. The TGA-defined conversion evolution was then modeled using a JMAK/Avrami form with Arrhenius temperature dependence to predict the isothermal holding time required to reach a target conversion at a selected dwell temperature. Relative to supplier-recommended profiles, the optimized profiles increased die-shear strength by 35% for the spherical-particle paste and by 206% for the flake-based paste, and promoted a fracture-mode transition from interfacial debonding toward mixed/cohesive fracture. Pearson/Ridge baselines and attention-based multiple-instance learning (MIL) linked strength and fracture-mode distribution to porosity/connectivity-related descriptors; paste-wise normalization mitigated paste-specific baselines and enabled MIL to reveal profile-induced microstructure–performance co-variation. Overall, this study establishes a practical workflow that couples thermal-kinetics-guided profile design with mechanical and fractographic validation and interpretable microstructure–property attribution, supporting mechanism-informed optimization of pressureless sintered Ag die-attach pastes. ...
Conference paper (2026) - L. Du, Chenshan Gao, Tianxing Du, G.Q. Zhang, Huaiyu Ye
In this study, the morphology-dependent microstructure and fracture toughness of pressure-assisted sintered copper (Cu) particles are investigated using focused ion beam scanning electron microscopy (FIB-SEM) reconstruction, transmission Kikuchi diffraction (TKD), micro-cantilever bending experiments, and molecular dynamics (MD) simulations. Three representative particle systems are examined, namely monomodal, bimodal, and flake-shaped particles. Three-dimensional FIB-SEM reconstructions show that particle morphology strongly influences densification, with porosities of approximately 13.2%, 6.7%, and 17.8% for the monomodal, bimodal, and flake-shaped systems, respectively. The bimodal particles form the most densified microstructure due to hierarchical packing, where smaller particles occupy interstitial regions between larger particles. TKD analyses further reveal morphology-dependent neck structures and grain distribution, where bimodal particles develop more continuous interparticle necks, whereas flake-shaped particles exhibit lamellar interfaces with residual interlamellar pores. Fracture toughness measurements demonstrate a strong dependence on particle morphology. The bimodal sample exhibits the highest fracture resistance, with J2% of approximately 129 J/m2 and KJ of about 3.6 MPa m1/2. The monomodal sample shows significantly lower resistance, with J2% of approximately 49 J/m2 and KJ of about 1.8 MPa m1/2. The flake-shaped sample shows an intermediate J2% value of approximately 98 J/m2, but a lower KJ of about 0.9 MPa m1/2. MD simulations further reveal that particle morphology governs strain localization, dislocation activity, and crack propagation mechanisms. ...
Silicon carbide (SiC) MOS structures are promising for high voltage and high temperature power electronics, but gate oxide breakdown remains a major reliability concern because of its stochastic nature and the limited accessibility of the underlying failure pathway. In this work, a defect-informed phase- field framework is developed to investigate oxide breakdown in SiC MOS structures. The model is initialized using a depth- resolved pre-existing defect profile extracted from capacitance and conductance frequency response, thereby linking electrical characterization with physics-based breakdown simulation. The results show that breakdown starts from localized nucleation at defect-rich weak points near the SiO2 /SiC interface, followed by directional growth, interaction, and coalescence of degraded regions into a through-thickness conductive path. Combined analysis of the phase-field variable and electric field distribution shows that local electric field redistribution plays a key role in guiding conductive path propagation and determining the final breakdown trajectory. Post-breakdown focused ion beam scanning electron microscopy (FIB-SEM) reveals a tortuous and spatially confined channel morphology, consistent with the defect-assisted and field-driven breakdown picture predicted by the model. The proposed framework provides a useful tool for analyzing breakdown trajectories and gate oxide reliability in SiC power devices. ...
This work proposes a one-stage bidirectional rectifier with a pre-charge voltage (VPC) based perturb-and-observe (P&O) maximum power point tracking (MPPT) algorithm for triboelectric energy harvesting. The proposed VPC-based MPPT dynamically locates the true MPP while accounting for circuit non-idealities, using a simplified implementation compared to conventional P&O methods. Consequently, it achieves 93% MPPT efficiency and 8.86× energy enhancement compared to the full-bridge rectifier. ...
Conference paper (2026) - Letao Bian, Xinyue Wang, Jing Zhang, Jianhao Wang, G.Q. Zhang, Kim S. Siow, Pan Liu
This study investigates the corrosion mechanisms at the interfaces of sintered joints exposed to H2S for offshore applications. Through finite element modeling and experimental validation, the galvanic corrosion behavior of four sintered joint configurations was analyzed. Simulation results identified the interface as the primary corrosion zone, with accelerated degradation driven by galvanic coupling. Polarization and electrical conductivity measurements further confirmed that sintered silver maintains corrosion resistance and stable electrical properties after corrosion. This work focused on the interfacial corrosion mechanism and provides insights for offshore power module packages. ...

An experimental study of mounting-pressure effects in microchip assembly

This work presents an experimental investigation of adhesive-based die attachment using the Drop-Attach technique, compared with the conventional pick-and-place method. Drop-Attach is a contactless process that eliminates the mechanical stresses inherent to force-assisted placement. In this method, dies are optically aligned and released—via a short air pulse—from a height of 100–300 μm above a substrate coated with a flat adhesive layer, enabling pressure-free, contactless placement. The process achieves smaller cycle times, potentially improving the throughput over conventional methods that require additional time for deceleration and bonding-force buildup. To assess feasibility and performance, a silver-filled bismaleimide/acrylate adhesive was printed on ENIG-finished pads, and dummy silicon dies with Au-, Ag-, and Cu-coated surfaces were assembled using both techniques. Bond quality was comprehensively analysed through measurements of bond line thickness, die tilt, void formation, die-shear strength, failure mechanisms, and electrical performance. Drop-Attach achieved minimal die tilt (≤0.1°) and uniform BLTs, though higher voiding and ∼9.55% increased electrical resistance were observed. The lower shear strength was primarily attributed to the absence of adhesive fillet formation rather than the lack of applied pressure. While trade-offs remain, this study demonstrates the feasibility of adhesive-based die attachment using the Drop-Attach method, which enables faster cycle times and higher throughput while significantly reducing mechanical stresses. These advantages position Drop-Attach as a promising technique for next-generation semiconductor packaging. ...