Yaguo Wang

Femtosecond (fs) laser sintering of metallic nanoparticles offers a powerful route for additive manufacturing of conductive layers, but its application to copper nanoparticles (Cu NPs) is constrained by hot-electron-driven ablation and a narrow sintering window. Our prior studies showed that double-pulse fs irradiation can mitigate these effects by lowering the peak electron temperature. Building on this foundation, the present work demonstrates that integrating controlled substrate heating with double-pulse femtosecond sintering improves film quality by suppressing ablation and enhancing densification. Systematic evaluation under four thermal conditions—ambient, 60 °C, 120 °C, and sequential 60→120 °C—shows that substrate heating promotes more uniform microstructures and reduces roughness from Sa = 0.385 μm to 0.101 μm. The sequential heating strategy delivers the best film quality, achieving 97–98% coverage, < 3% porosity, and the highest hardness of 189.7 ± 54.8 MPa. Substrate heating also strengthens reductive sintering, increasing the measured Cu/O ratio to 23.40 at 60 °C and reducing oxygen content relative to the non-heating case. Overall, this combined thermal-ultrafast approach enables Cu films with improved oxidation resistance, higher film density and reduced porosity, although a dedicated long-term oxidation study was not performed.

Cross-plane heat transport is a critical bottleneck for van der Waals (vdW) electronics, yet its microscopic governing principles remain elusive. We demonstrate that stacking order is an effective control knob for cross-plane phonon transport in multilayer Rhenium Disulfide (ReS2). Thickness-dependent thermal conductivity measurements reveal remarkably long cross-plane phonon mean free paths (MFPs) (&gt;= 200-300 nm) and provide a direct experimental observation of the transition from quasi-ballistic transport to a thickness-independent ballistic limit. AA stacking exhibits nearly double the cross-plane thermal conductivity of AB stacking, driven by longer acoustic phonon lifetimes from a more "coherent" interlayer registry. Integrated deep neural-network molecular dynamics reveals that phonon filtering in ReS2 is fundamentally frequency-selective: weak vdW coupling acts as a low-pass filter, whereas stronger coupling broadens the transmission passband. These results establish ReS2 as a model system where stacking order and interlayer coupling can be engineered to tune heat conduction across diffusive, quasi-ballistic, and ballistic regimes, offering a new framework for thermal management in 2D electronics.

Cross-plane heat transport is a critical bottleneck for van der Waals (vdW) electronics, yet its microscopic governing principles remain elusive. We demonstrate that stacking order is an effective control knob for cross-plane phonon transport in multilayer Rhenium Disulfide (ReS2). Thickness-dependent thermal conductivity measurements reveal remarkably long cross-plane phonon mean free paths (MFPs) (>= 200-300 nm) and provide a direct experimental observation of the transition from quasi-ballistic transport to a thickness-independent ballistic limit. AA stacking exhibits nearly double the cross-plane thermal conductivity of AB stacking, driven by longer acoustic phonon lifetimes from a more "coherent" interlayer registry. Integrated deep neural-network molecular dynamics reveals that phonon filtering in ReS2 is fundamentally frequency-selective: weak vdW coupling acts as a low-pass filter, whereas stronger coupling broadens the transmission passband. These results establish ReS2 as a model system where stacking order and interlayer coupling can be engineered to tune heat conduction across diffusive, quasi-ballistic, and ballistic regimes, offering a new framework for thermal management in 2D electronics.

Femtosecond (fs) laser sintering enables ultrafast and spatially localized energy deposition, making it attractive for additive manufacturing of metal nanoparticles. However, undesired ablation during fs irradiation of copper (Cu) nanoparticles often disrupts uniform sintering, and the underlying ablation mechanisms remain poorly understood. In this work, we investigate the fragmentation and coalescence behavior of Cu nanoparticles subjected to fs laser scanning under fluence conditions relevant to sintering applications. Particle size distributions extracted from scanning electron microscopy reveal a bimodal transformation: emergence of sub-60 nm debris and formation of large aggregates up to 750 nm. We evaluate two candidate mechanisms—Coulomb explosion and hot electron blast—by estimating electron emission, electrostatic pressure, and hot electron temperature using the Richardson–Dushman equation and two-temperature modeling. Our analysis shows that Coulomb explosion is unlikely under the laser fluence used (∼27 mJ/cm2), as the estimated electrostatic pressure (∼4 kPa) is orders of magnitude below the cohesive strength of Cu. In contrast, hot electron blast is identified as the dominant ablation pathway, with electron temperatures exceeding 5000 K and resulting blast pressures above 6 GPa. Thermal modeling also suggests moderate lattice heating (∼930 K), enabling softening and fusion of partially fragmented particles. These results confirm that fs laser-induced ablation in Cu nanoparticles is driven predominantly by nonthermal electron dynamics rather than classical melting or evaporation. Importantly, this work highlights that reducing hot electron temperature—such as through double-pulse irradiation schemes—can effectively suppress ablation and expand the sintering window, offering a promising strategy for precision nanoscale additive manufacturing.

Flatbands, characterized by their dispersionless energy levels in electronic, magnetic, and phononic systems, hold substantial potential for advancements in electronics and quantum information processing. Most flatbands exist in thermal equilibrium and cannot be easily created or annihilated externally, limiting their flexibility as switchable knobs for use in microelectronics and quantum applications. In our work, we demonstrate the generation of a coherent phonon flatband in a GaAs/AlAs superlattice using 800 nm femtosecond laser pulses. This coherent phonon flatband does not correspond to a phonon eigenmode at equilibrium and exhibits strong coupling with two branches of coherently excited longitudinal phonon modes. With molecular dynamics simulations, we show more generally that the coherent phonon flatband can be induced by coherently and spatially modulated optical excitations of superlattice structures. Our results highlight a pathway for coherent phonon flatband creation in the time domain that can be generalized to various superlattice systems, potentially inspiring the realization of coherent flatband generation of other quasiparticles. Above-bandgap femtosecond laser pulses generate a coherent phonon flatband in a GaAs/AlAs superlattice captured using ultrafast X-ray diffraction, providing a way to control atomic vibrations for future electronic and quantum technologies.

Femtosecond (fs) laser sintering enables ultrafast and spatially localized energy deposition, making it attractive for additive manufacturing of metal nanoparticles. However, undesired ablation during fs irradiation of copper (Cu) nanoparticles often disrupts uniform sintering, and the underlying ablation mechanisms remain poorly understood. In this work, we investigate the fragmentation and coalescence behavior of Cu nanoparticles subjected to fs laser scanning under fluence conditions relevant to sintering applications. Particle size distributions extracted from scanning electron microscopy reveal a bimodal transformation: emergence of sub-60\,nm debris and formation of large aggregates up to 750 nm. We evaluate two candidate mechanisms -- Coulomb explosion and hot electron blast -- by estimating electron emission, electrostatic pressure, and hot electron temperature using the Richardson--Dushman equation and two-temperature modeling. Our analysis shows that Coulomb explosion is unlikely under the laser fluence used ($\sim$27\,mJ/cm$^2$), as the estimated electrostatic pressure ($\sim$4 kPa) is orders of magnitude below the cohesive strength of Cu. In contrast, hot electron blast is identified as the dominant ablation pathway, with electron temperatures exceeding 5,000 K and resulting blast pressures above 4 GPa. Thermal modeling also suggests moderate lattice heating ($\sim$930\,K), enabling softening and fusion of partially fragmented particles. These results confirm that fs laser-induced ablation in Cu nanoparticles is driven predominantly by nonthermal electron dynamics rather than classical melting or evaporation. Importantly, this work highlights that reducing hot electron temperature -- such as through double-pulse irradiation schemes -- can effectively suppress ablation and expand the sintering window, offering a promising strategy for precision nanoscale additive manufacturing.

Abstract Microwave (MW) plasma, as an electrodeless non-thermal plasma technique, holds significant potential for gas processing applications under near-ambient conditions. However, current MW plasma methods suffer from low energy efficiency due to the high power required for molecular breakdown via vibrational excitation. A promising approach to mitigate this challenge involves using a pair of high relative permittivity dielectric resonators (DRs) in close proximity to enhance the electric field within the small gap between them, thus reducing power consumption. In this study, we combined simulations and experiments to investigate the electric field enhancement effect of DRs with varying shapes, geometrical parameters (e.g., radius and height), gap distances, and orientations relative to the electric field polarization and MW propagation directions. Simulations performed using Ansys HFSS demonstrate that edge-to-edge configurations of hexagonal, square, and triangular prism DRs can achieve significant electric field enhancement over a broad range of geometric parameters. DRs fabricated from calcium titanate were tested experimentally using a simple setup with a kitchen microwave (2.45 GHz) at ambient pressure. With input power below 100 W, stable and highly confined plasma was generated using hexagonal and triangular prism DRs. These results suggest a simple, cost-effective, and low-power method for generating MW plasma under ambient conditions, offering particular advantages for chemical processing in rural areas utilizing renewable energy resources.

Carbon materials display intriguing physical properties, including superconductivity and highly anisotropic thermal conductivity found in graphene. Compressive strain can induce structural and bonding transitions in carbon materials and create new carbon phases, but their interplay with thermal conductivity remains largely unexplored. We investigated the in situ high-pressure thermal conductivity of compressed graphitic phases using picosecond transient thermoreflectance and first-principles calculations. Our results show an anomalous thermal conductivity that peaks to 260 W/mK at 15-20 GPa but drops to 3.0 W/mK at ∼35 GPa. Together with complimentary in situ Raman and x-ray diffraction results, the abnormal thermal conductivity trend of compressed carbon is attributed to phonon-mediated conductivity influenced by interlayer buckling and sp^{2} to sp^{3} transition and, subsequently, the formation of M-carbon nanocrystals and amorphous carbon. Strain-induced structural and bonding variations provide a wide-range manipulation of thermal and mechanical properties in carbon materials.

Abstract Tropical fruits are popular worldwide due to their appealing flavors and diverse health benefits. However, a significant amount of waste is caused by inferior fruits that are partly eliminated from the fresh fruit market and by‐products produced during transportation, storage, and processing. With increasing focus on environmental sustainability and resource conservation, recycling waste resources from tropical fruits has emerged as a hot topic of interest. Fruit‐derived starch is an emerging approach to adding value for some tropical fruit waste and inferior fruits. This review article briefly overviews extraction methods, chemical composition, structural characteristics, physical and chemical properties, physiological benefits, modification techniques, and potential applications of new tropical fruit‐derived starch. Compared with traditional starch, tropical fruit‐derived starch exhibits unique structural and processing attributes, making it suitable as a supplement or replacement for industrial starch in the food industry. Moreover, tropical fruit‐derived starch retains the rich nutrients and functional components present in fruits to some extent, thereby offering potential health benefits and greater consumer acceptance. Although current research on starch derived from tropical fruits is primarily at the laboratory stage, and there is limited exploration of its processing and application, evolving lifestyle trends and heightened health awareness are expected to foster its further development and utilization, paving the way for large‐scale commercialization and driving future market growth.

Tuberculosis (TB) is a major fatal infectious disease globally, exhibiting high morbidity rates and impacting public health and other socio-economic factors. However, some individuals are resistant to TB infection and are referred to as "Resisters". Resisters remain uninfected even after exposure to high load of Mycobacterium tuberculosis (Mtb). To delineate this further, this study aimed to investigate the factors and mechanisms influencing the Mtb resistance phenotype. We assayed the phagocytic capacity of peripheral blood mononuclear cells (PBMCs) collected from Resisters, patients with latent TB infection (LTBI), and patients with active TB (ATB), following infection with fluorescent Mycobacterium bovis Bacillus Calmette-Guérin (BCG). Phagocytosis was stronger in PBMCs from ATB patients, and comparable in LTBI patients and Resisters. Subsequently, phagocytes were isolated and subjected to whole transcriptome sequencing and small RNA sequencing to analyze transcriptional expression profiles and identify potential targets associated with the resistance phenotype. The results revealed that a total of 277 mRNAs, 589 long non-coding RNAs, 523 circular RNAs, and 35 microRNAs were differentially expressed in Resisters and LTBI patients. Further, the endogenous competitive RNA (ceRNA) network was constructed from differentially expressed genes after screening. Bioinformatics, statistical analysis, and quantitative real-time polymerase chain reaction were used for the identification and validation of potential crucial targets in the ceRNA network. As a result, we obtained a ceRNA network that contributes to the resistance phenotype. TCONS_00034796-F3, ENST00000629441-DDX43, hsa-ATAD3A_0003-CYP17A1, and XR_932996.2-CERS1 may be crucial association pairs for resistance to TB infection. Overall, this study demonstrated that the phagocytic capacity of PBMCs was not a determinant of the resistance phenotype and that some non-coding RNAs could be involved in the natural resistance to TB infection through a ceRNA mechanism.

OBJECTIVES We elucidated the factors, evolution, and compensation of antimicrobial resistance (AMR) in Mycobacterium tuberculosis (MTB) isolates under dual pressure from the intra-host environment and anti-tuberculosis (anti-TB) drugs. METHODS This retrospective case-control study included 337 patients with pulmonary tuberculosis from 15 clinics in Tianjin, China, with phenotypic drug susceptibility testing (DST) results available for at least two time points between January 1, 2009 and December 31, 2016. Patients in the case group exhibited acquired AMR to isoniazid (INH) and/or rifampicin (RIF), while those in the control group lacked acquired AMR. Whole-genome sequencing (WGS) was conducted on 149 serial longitudinal MTB isolates from 46 patients who acquired or reversed phenotypic INH/RIF-resistance during treatment. The genetic basis, associated factors, and intra-host evolution of acquired phenotypic INH/RIF-resistance were elucidated using a combined analysis. RESULTS Anti-TB interruption duration ≥30 d showed association with acquired phenotypic INH/RIF resistance (aOR=2·2, 95%CI: 1·0-5·1) and new rpoB mutations (P = 0·024). MTB evolution was 1·2 (95% CI: 1·02-1·38) single nucleotide polymorphisms per genome per year under dual pressure from the intra-host environment and anti-TB drugs. AMR-associated mutations occurred before phenotypic AMR appearance in cases with acquired phenotypic INH (10/16) and RIF (9/22) resistances. CONCLUSIONS Compensatory evolution may promote the fixation of INH/RIF-resistance mutations and affect phenotypic AMR. TB treatment should be adjusted based on gene sequencing results, especially in persistent culture positivity during treatment, which highlight the clinical importance of WGS in identifying reinfection and AMR acquisition before phenotypic DST.

Introduction: Mycobacterium tuberculosis (MTB) has a type III-A clustered regularly interspaced short palindromic repeat/CRISPR-associated protein (CRISPR/Cas) system consisting of a Csm1-5 and CRISPR RNA (crRNA) complex involved in the defense against invading nucleic acids. However, CRISPR/Cas system in the MTB still is clearly unknown and needs to be further explored. Methods: In our work, two non-Cas system proteins EspB and HtpG protein were found and identified by LC-MS/MS. The effect of EspB and HtpG on Type III-A CRISPR/Cas System of M. tuberculosis was examined by using Plasmid interference assay and Co-immunoprecipitation analyses. We explored that EspB could interact with the crRNA RNP complex, but HtpG could inhibit the accumulation of the MTB Csm proteins and defense the mechanism of CRISPR/Cas system. Results: The proteins ESAT-6 secretion system-1(Esx-1) secreted protein B (EspB) and high-temperature protein G (HtpG), which were not previously associated with CRISPR/Cas systems, are involved in mycobacterial CRISPR/Cas systems with distinct functions. Conclusion: EspB is a novel crRNA-binding protein that interacts directly with the MTB crRNP complex. Meanwhile, HtpG influences the accumulation of MTB Csm proteins and EspB and interferes with the defense mechanism of the crRNP complex against foreign DNA in vivo . Thereby, our study not only leads to developing more precise clinical diagnostic tool to quickly detect for MTB infection, but also knows these proteins merits for TB biomarkers/vaccine candidates.

Combining the picosecond transient thermoreflectance (ps-TTR) and picosecond laser flash (ps-LF) techniques, we have developed a novel method to simultaneously measure the thermal effusivity and the thermal diffusivity of metal thin films and determine the thermal conductivity (κ) and the heat capacity (cv) altogether. In order to validate our approach and evaluate the uncertainties, we analyzed five different metal films (Al, Cr, Ni, Pt, and Ti) with thicknesses ranging from 297 nm to 1.2 µm. Our results on thermal transport properties and heat capacity are consistent with reference values, with the uncertainties for the thermal conductivity and the heat capacity measurements below 25% and 15%, respectively. Compared with the ps-TTR technique alone, the combined approach substantially lowers the uncertainty of the thermal conductivity measurement. Uncertainty analyses on various materials show that this combined approach is capable of measuring most of the materials with a wide range of thicknesses, including those with low thermal conductivity (e.g., mica) down to thicknesses as small as 60 nm and ultrahigh thermal conductivity materials (such as cubic BAs) down to 1400 nm. Simultaneous measurement of thermal conductivity and heat capacity enables exploration of the thermal physical behavior of materials under various thermodynamic and mechanical perturbations, with potential applications in thermal management materials, solid-state phase transitions, and beyond.

As a branch of laser powder bed fusion, selective laser sintering (SLS) with femtosecond (fs) lasers and metal nanoparticles (NPs) can achieve high precision and dense submicron features with reduced residual stress, due to the extremely short pulse duration. Successful sintering of metal NPs with fs laser is challenging due to the ablation caused by hot electron effects. In this study, a double-pulse sintering strategy with a pair of time-delayed fs-laser pulses is proposed for controlling the electron temperature while still maintaining a high enough lattice temperature. We demonstrate that when delay time is slightly longer than the electron-phonon coupling time of Cu NPs, the ablation area was drastically reduced and the power window for successful sintering was extended by about two times. Simultaneously, the heat-affected zone can be reduced by 66% (area). This new strategy can be adopted for all the SLS processes with fs laser and unlock the power of SLS with fs lasers for future applications.