Craig B. Arnold

ABSTRACT As demands for sustainable and scalable energy materials manufacturing accelerate, additive manufacturing (AM) remains largely limited to passive shaping of predefined precursors. Here, we introduce reactive laser AM, in which precursor composition is designed to transform the printing step itself into a chemically active stage of materials synthesis. Incorporating eutectic alkali halide salts into protein‐based powders converts localized laser heating into transient reaction environments that drive vapor‐phase chemistry, surface etching, and in situ hierarchical growth without external reagents or solvents. This internally activated reactivity enables the rapid formation of graphitic aerogel monoliths with multilevel architecture—macroporous frameworks decorated with microtubular arrays and nanoscale features—within seconds in a single process. As energy storage electrodes, these hierarchically structured aerogels exhibit a tenfold enhancement in gravimetric capacitance (∼162 F g −1 ) relative to salt‐free counterparts. By engineering reactivity through feedstock design, this work reframes laser AM as a dynamic platform for reaction‐driven materials‐by‐design.

Laser processing has emerged as a powerful and versatile tool for the synthesis and patterning of nanomaterials, offering high spatial resolution, material versatility, and digital control. In our recent work, we have developed a laser-based method for producing graphitic aerogels (GAs), or macroscale assemblies of nanometer-sized graphitic structures, by integrating principles of laser powder bed fusion with localized laser pyrolysis. Uniquely, this technique uses hemoglobin, a protein-rich biowaste derived from animal blood, as the precursor. Upon laser irradiation, the hemoglobin undergoes rapid thermal decomposition and in situ graphitization, forming 3D macroporous networks without the need for additional binders, templates, or harsh chemical treatments. Here we discuss the application of this process and materials to symmetrical 3D supercapacitors. The fabricated supercapacitors exhibit a high specific capacitance and excellent cycle stabilitys, attributable to the laser-engineered architecture facilitating ion diffusion even for thick electrodes.

Laser-based metal manufacturing techniques, such as laser welding and additive manufacturing, offer high precision and versatility, but the complex melting and resolidification processes often lead to uneven surface morphologies. This study investigates the effects of dynamically modulated bimodal beam shaping on metal surface topography. Two independently controlled Gaussian beams were super-positioned, with one beam oscillating sinusoidally to modulate the bimodal intensity profile both spatially and temporally during laser processing. At low oscillation frequencies, periodic surface features emerged, whereas high modulation frequencies produced smooth melt tracks. Simulations indicate that higher frequencies promote a more uniform spatial energy distribution and reduce melt durations. These results highlight the potential of tuning dynamic bimodal beam shaping parameters to actively control and suppress unwanted surface features, offering a framework for improving surface quality in laser-based manufacturing processes.

ABSTRACT As electronic systems become increasingly integrated into daily life, the demand for lightweight, effective, and environmentally sustainable materials for electromagnetic interference (EMI) shielding continues to grow. In this study, we investigate the EMI shielding performance of hierarchically porous graphitic aerogels (HGAs) synthesized from albumen protein through controlled pyrolysis. These single‐component, bio‐derived aerogels differ from conventional carbon aerogels by combining ultralow density, hierarchical porosity, and tunable electrical conductivity without templating, chemical activation, surface functionalization, or multistep processing. By varying the carbonization temperature, heating rate, and sample thickness, we demonstrate direct control over the aerogel's microstructure, density, and electrical properties, and consequently, the EMI shielding behavior. The HGA exhibits an outstanding specific shielding effectiveness of over 16 200 dB cm 2 g − 1 , outperforming previously reported single‐component carbon‐based aerogels synthesized through simple pyrolysis by more than an order of magnitude. Furthermore, we show that processing conditions can be used to deliberately control the dominant attenuation mechanism, enabling a shift from reflection‐dominated to absorption‐dominated shielding behavior, with the latter being particularly promising for mitigating secondary electromagnetic pollution. These findings establish protein‐derived, single‐component HGAs as a simple, tunable, and high‐performance platform for EMI shielding, with broad implications for aerospace, electronics, and future wireless communication technologies.

The dynamics of the melt pool critically influence the structure and resultant properties of resolidified metals in laser-based powder bed fusion and related 3D printed applications. While the influence of external electric fields on the surface and bulk properties of fluids at ambient conditions is well documented, their impact on the transient, high-temperature melt pools characteristic of powder bed fusion remains largely unexplored, and their broader applicability is unclear across multiple length scales. Here, we reveal how external non-contact EFs influence both macro- and microstructures during laser scanning. EFs have the ability to influence structure through a fundamentally different mechanism than thermal approaches. Qualitative and quantitative analyses show that EFs drastically improve continuity and stability of metal tracks while enhancing surface smoothness in micro- and nano-scale. Beyond the surface, EFs drive the formation of equiaxed grains, promoting grain refinement in bulk. Structural effects depend on EF type as well as the orientation and direction with respect to the laser scanning direction. Moreover, we demonstrate that EFs can be effectively coupled with advanced beam-shaping strategies, yielding synergistic structural control and indicating their potential as a versatile and adaptable tool for next-generation advanced manufacturing systems.

Hierarchically porous graphitic aerogels (HGAs) are promising carbon materials owing to their low density, multilevel porosity, and interconnected frameworks, making them suitable for applications in energy storage, water purification, and environmental remediation. In this work, HGAs were synthesized from a range of protein-based precursors, including pasteurized egg white (PEW), α-lactalbumin, β-lactoglobulin, bovine serum albumin (BSA), and yogurt, through pyrolysis. The study investigates how precursor composition influences thermal decomposition and microstructural development. All precursors except yogurt formed interconnected sheet- and fiber-like frameworks due to the self-foaming effect during pyrolysis. Despite its high protein content, the yogurt precursor produced a rough porous morphology, likely due to the presence of fats and inorganic species that inhibit foaming action. Elemental analysis confirmed the presence of significant amounts of inorganic species, such as calcium and phosphorus, in the yogurt-derived samples. To examine the influence of nonprotein constituents, a control experiment was conducted using a casein-whey mixture, the primary protein component of yogurt. Pyrolysis of this mixture produced aerogels with interconnected sheet- and fiber-like morphologies, confirming that the additional nonprotein components in yogurt affect structure formation. Further Raman analysis indicates that increasing the pyrolysis temperature enhanced carbonization and graphitic ordering across all the samples. Overall, this work provides insight into developing HGAs from diverse protein precursors and shows how precursor composition influences microstructural development during protein pyrolysis, offering valuable guidance for the design of HGA-based composites and functional materials.

Anode-free solid-state batteries (AF-SSBs) present a promising pathway toward sustainable transportation by eliminating the lithium-metal anode and using a bare current collector (CC) with a high-energy-density cathode and solid electrolyte (SE). 1 This design offers improved safety, recyclability, and energy performance—achieving specific energies >500 Wh/kg and projected costs <$100/kWh—compared to conventional Li-ion batteries. 2 Recent progress includes lithium-metal-free configurations; however, critical challenges related to interfacial stability limit their practical adoption. 3-7 A major limitation is the electro-chemo-mechanical instability of buried interfaces—particularly CC|SE, SE|Li, and CC|Li—during cycling. 8 These interfaces undergo complex morphological changes during lithium plating yet remain difficult to probe due to their buried and highly localized nature. To establish precise structure–property–performance relationships , in situ and operando 3D investigations of lithium plating at these solid–solid interfaces are critical. 9 This work investigates how lithium plating at the CC|SE interface correlates with mechanical instabilities—such as fracture widening and lithium intrusion into cracks—across current densities. We address two open questions critical to understanding failure modes in AF-SSBs: Q1: Is lithium penetration into SE fractures at low and high current densities solely electrochemically driven, or is it partially due to lithium extrusion during assembly? Q2: What is the origin of lithium observed within fractures—pre-existing or resulting from electrochemical cycling? To answer these, we used simultaneous in situ neutron and X-ray micro-computed tomography (NeXT), as well as standalone in situ neutron tomography. NeXT experiments were performed at the Institut Laue-Langevin (ILL) 10 using a custom-designed electrochemical cell with ~4–6 µm spatial resolution. 11 Complementary neutron tomography was conducted at Oak Ridge National Laboratory (ORNL), 12 achieving an effective spatial resolution of 20–30 µm. We imaged five batteries: three pristine, one cycled at low current density (0.5 µA), and one at high current density (5 µA). X-ray tomography revealed pre-existing cracks near the SE pellet edges in pristine cells and crack widening at the center in both cycled cells. Neutron tomography showed no lithium in one pristine cell (ILL), while two pristine cells (ORNL) displayed lithium near the start of fractures at the Li|SE interface—likely due to lithium extrusion during assembly. However, deep lithium penetration was not observed in these pristine cells. In plated cells (ILL), lithium accumulated within fractures—showing "filament-like" morphology at low current density and "flow-like" behavior at high current. We also observed interfacial void formation and contact loss at the CC|SE interface. Interestingly, no lithium plated directly on the stainless-steel CC at high current, likely due to lithium being redirected into SE fractures. Limited plating on the CC was observed at low current density. Our findings suggest that fracture widening may be driven by electrochemical forces, especially under high current density. Moreover, lithium penetration into SE fractures likely results from a combination of initial extrusion and subsequent electrochemical driving forces. We hypothesize that visco-plastic deformation governs lithium intrusion during cycling, consistent with electro-chemo-mechanical phase-field modeling. 13 To conclusively determine the mechanisms behind lithium intrusion and its origin, operando time-resolved neutron and X-ray imaging studies are currently underway. This work advances mechanistic insight into buried solid–solid interfacial degradation in AF-SSBs and informs the design of more robust architectures for next-generation electric vehicle batteries. References: Nanda, J., et al. (2018). MRS Bulletin , 43 (10), 740-745. Heubner, C., et al. (2021). Advanced Functional Materials , 31 (51), 2106608. Herle, S., et al. (2020). Challenges for and Pathways Toward Solid-State Batteries (No. ORNL/TM-2020/1747). Oak Ridge National Lab.(ORNL), Oak Ridge, TN (United States). Albertus, P., et al. (2021). ACS Energy Letters , 1399-1404. Krauskopf, T., et al. (2020). Chemical reviews , 120 (15), 7745-7794. Hatzell, K. B., et al. (2020). ACS Energy Letters , 5 (3), 922-934. Yu, Z., et al. (2021). Advanced Energy Materials , 11 (18), 2003250. Kazyak, E., et al. (2022). Matter , 5 (11), 3912-3934. Lou, S., et al. (2020). Chem , 6 (9), 2199-2218. Tengattini, A., et al. (2020). Nuclear Instruments and Methods in Physics Research

This study investigates polarization-dependent photoinduced effects in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{As}_{2} \mathrm{S}_{3}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{As}_{2} \text{Se}_{3}$</tex> thin films excited by fslaser pulses operating in the telecommunications range. The findings demonstrated the localized formation of structural defects, including crystallization, and revealed anisotropyinduced birefringence that varied with laser parameters.

Chemical recycling of plastics to monomers offers a promising strategy to address massive plastic waste. However, most chemical recycling methods are narrowly limited to specific polymer resins. Pyrolysis offers generality for universal polymer recycling, but energy inefficiencies and degradation products as a result of overheating make this strategy less practical. Herein, we report a photothermal depolymerization approach that is general to numerous polymers with high selectivity. We identified hierarchical porous carbon material upcycled from proteins as a high surface area photothermal agent without requiring direct incorporation into polymer resin. We successfully depolymerize a wide range of polymers, including polystyrene (PS), poly(methyl methacrylate) (PMMA), polyvinyl acetate (PVA), polyvinyl alcohol (PVOH), trans-polyisoprene, polypropylene carbonate (PPC), poly(L-lactide) (PLLA), polyethylene terephthalate (PET), and polycarbonate (PC). Additionally, the porous carbon material has extended lifetime (can be used at least 5 cycles) by sequential addition of polystyrene films to the post-reacted porous carbon materials. Excitingly, this method is broadly applicable to post-consumer plastics without preprocessing and is readily scalable, demonstrating the versatility of this closed-loop chemical recycling approach.

Abstract The prediction of crystal properties plays a crucial role in materials science and applications. Current methods for predicting crystal properties focus on modeling crystal structures using graph neural networks (GNNs). However, accurately modeling the complex interactions between atoms and molecules within a crystal remains a challenge. Surprisingly, predicting crystal properties from crystal text descriptions is understudied, despite the rich information and expressiveness that text data offer. In this paper, we develop and make public a benchmark dataset (TextEdge) that contains crystal text descriptions with their properties. We then propose LLM-Prop, a method that leverages the general-purpose learning capabilities of large language models (LLMs) to predict properties of crystals from their text descriptions. LLM-Prop outperforms the current state-of-the-art GNN-based methods by approximately 8% on predicting band gap, 3% on classifying whether the band gap is direct or indirect, and 65% on predicting unit cell volume, and yields comparable performance on predicting formation energy per atom, energy per atom, and energy above hull. LLM-Prop also outperforms the fine-tuned MatBERT, a domain-specific pre-trained BERT model, despite having 3 times fewer parameters. We further fine-tune the LLM-Prop model directly on CIF files and condensed structure information generated by Robocrystallographer and found that LLM-Prop fine-tuned on text descriptions provides a better performance on average. Our empirical results highlight the importance of having a natural language input to LLMs to accurately predict crystal properties and the current inability of GNNs to capture information pertaining to space group symmetry and Wyckoff sites for accurate crystal property prediction.

Hierarchically porous monolithic graphitic sheet-based aerogels (HGA) with high surface area and ultralow density have drawn massive attention for applications in catalysis, energy storage/conversion, water purification, and beyond. However, syntheses of these materials rely on harsh and nonsustainable chemical reagents and/or template-based methods, while the resulting structures generally lack covalent integration, compromising their properties. Herein, we demonstrate a self-foaming mechanism for green and scalable synthesis of HGA using protein precursors. Rather than creating a solid composite and exchanging the sacrificial component with a gas phase, we create a gas phase first and then convert the liquid into a solid phase. The controlled heating of protein induces intrinsic foaming via softening, gas evolution, and carbonization/graphitization, resulting in an HGA composed of a sheet and fiber-like framework. Our investigation of processing-structure–property relationships elucidates the interplay between synthesis variables and aerogel structure/properties, enabling deliberate control over microstructural features. Notably, we demonstrate more than an order-of-magnitude variation in density and over a 7-fold increase in compressive strength by controlling the synthesis protocol. This study opens doors to a green and scalable approach to synthesizing HGAs with customizable microstructures and properties, making them promising for a broad spectrum of applications such as environmental remediation and energy storage.

The typical graphitisation process involves non-renewable carbon sources and high temperatures, which lead to increased carbon dioxide emissions and energy consumption in the resulting graphite. Biocarbon derived from biomass acts as a sustainable carbon source that can be graphitised at lower temperatures with the aid of catalysts. This review highlights the significance of both multi- and single-metallic catalytic graphitisation of biocarbon. Introducing a catalyst offers an effective means to modify the graphitisation conditions and the characteristics of graphitic layers formed at the atomic and molecular levels. Multi-metal catalysts demonstrate superior effectiveness in lowering the graphitisation temperature to 800 °C compared to single-metal catalysts (1000–1800 °C) and those without catalysts (>2000 °C), where the synergistic interaction of two distinct metals enhances the transformation of amorphous carbon into graphitic biocarbon, as opposed to single-metal catalysts. This paper establishes a hierarchy of the graphitisation conditions as follows: temperature > carbon precursors > heating rate. Furthermore, this work outlines the existing knowledge gap regarding metallic catalysts and clarifies the roles of transition, alkaline, and alkaline earth metal catalysts in the graphitisation of bioresources.

Three-dimensional (3D) cellular monoliths of graphitic materials, or Graphitic Aerogels (GAs), exhibit unique material properties offering applications in catalysis and energy storage. While conventional solution-based techniques enable the mass-production of GAs, the resulting features are highly randomized, and architecture-tunability had remained a challenge. Recently, the use of Additive Manufacturing (AM) towards the 3D printing of freeform GAs has been explored. The AM-printed GAs exhibit considerably improved performances, reinforcing the value of architecture-engineering capabilities. In this study, we demonstrate the laser-based 3D printing of freeform GAs by employing the concept of laser-based Powder Bed Fusion (PBF) using hemoglobin as the feedstock material, an iron-containing protein found in red-blood cells. Hemoglobin is an abundantly available biomass that is a common biowaste of the meat industry, with millions of tons discarded yearly. Analogous to conventional PBF, a bed of the low value biowaste was deposited, and subsequently irradiated to convert and assemble a 3D cellular monolith composed of turbostratic graphite. This process can be easily scaled up by simply depositing another layer of hemoglobin powder and subsequently scanning the laser beam. Through the repetition of these steps, a 3D macrostructure with arbitrary micro-scaled cellular geometries can be printed through a layer-by-layer approach. The laser printed macrostructures exhibited a low density, high electrical conductivity, and high surface area, suitable for energy-storage applications. The current PBF-inspired technique offers the freeform printing of GAs without any additional templates, binders, or chemical solutions, and the renewable resource, hemoglobin, is the only raw material required for the entire printing process.

Here, an interconnected three-dimensional (3D) network of carbon fibers possessing nano-scaled ripples, or laser-induced periodic surface structures (LIPSS), is fabricated via laser processing with an 800-nm femtosecond laser. The unique architecture of the CF network realizes the coexistence of both ∼800-nm low-spatial frequency LIPSS (LSFL) and ∼100-nm high-spatial frequency LIPSS (HSFL) overlapping on the same fiber surface. It is suggested that LSFL formed through the interference with Fresnel diffraction patterns projected by the fiber edges, while HSFL formed through LSFL-splitting assisted by surface plasmons. Moreover, the fundamentally different formation mechanisms of the two types result in distinctively different LIPSS orientations, where the LSFL is structure-dependent and self-orients according to the fiber propagation direction, while the HSFL is structure-independent and self-orients perpendicularly to the polarization direction of the incident pulses. The findings not only introduce an optical approach to prepare nano-textured carbon materials for future energy and regenerative-medicine applications but also reveal important insights into the underlying formation mechanisms of LIPSS on complex three-dimensional surfaces.

Abstract Graphene aerogels (GAs) with engineered architectures are a promising material for applications ranging from filtration to energy storage/conversion. However, current preparation approaches involve the combination of multiple intrinsically‐different methodologies to achieve graphene‐synthesis and architecture‐engineering, complicating the entire procedure. Here, a novel approach to prepare GAs with engineered architectures based on the laser‐upcycling of protein biowaste, hemoglobin, is introduced. Laser scanning achieves graphene‐synthesis concurrently with architecture‐engineering through the localized graphitization of hemoglobin along the laser‐scan path, enabling the direct preparation of engineered GAs. The laser‐upcycled GAs are uniquely decorated with fibrous graphitic structures, which significantly improves the surface area. Such structural formation is attributable to the inherent iron content of hemoglobin which leads to the formation of iron‐based nanoparticles that catalyze the formation of nano‐structured graphene. By leveraging the high electrical conductivity and unique structural morphology, the laser‐upcycled GAs are applied as electrodes of symmetrical 3D supercapacitors. The fabricated supercapacitors exhibited a high specific capacitance (≈54.9 F g −1 ) and excellent cycle stability (≈94% retention), attributable to the laser‐engineered architecture facilitating ion diffusion even for thick electrodes. Not only does this study provide a novel approach to prepare GAs with engineered architectures but showcases the potential of laser‐upcycling in preparing advanced functional materials for future devices.

Spatially selective melting of metal materials by laser irradiation allows for the precise welding as well as the 3D printing of complex metal parts. However, the simple scanning of a conventional Gaussian beam typically results in a melt track with randomly distributed surface features due to the complex and dynamic behavior of the melt pool. In this study, the implications of utilizing a dynamically oscillating energy input on driving melt track fluctuations is investigated. Specifically, the laser intensity and/or intensity distribution is sinusoidally modulated at different scan speeds, and the effect of modulation frequency on the resulting surface features of the melt track is examined. The formation of periodically oriented surface features indicates an evident frequency coupling between the melt pool and the modulation frequency. Moreover, such a frequency coupling becomes most prominent under a specific modulation frequency, suggesting resonant behavior. The insights provided in this study will enable the development of novel methods, allowing for the control and/or mitigation of inherent fluctuations in the melt pool through laser-driven resonances.

H x CrS 2−δ is produced by the proton exchange of NaCrS 2 and features alternating layers of crystalline and amorphous lamella. It exhibits superior performance as a Na-ion battery electrode compared with its parent compound with faster Na + diffusion, higher capacity, and better cyclability. This work explores the nature of the unique biphasic structure of H x CrS 2−δ using both powder and single-crystal X-ray diffraction, as well as electron microscopy. Additionally, ex situ characterizations using X-ray absorption spectroscopy, X-ray total scattering, and magnetometry are employed to study the mechanism by which this superiority arises. These reveal that migration of Cr does not impede battery performance and may, in fact, be crucial to the observed performance improvements. These studies show that Cr redox is not only possible but abundant in H x CrS 2−δ while accessing it in NaCrS 2 at lower voltages results in irreversible structural transitions that limit cycling stability. Additionally, we highlight the potential of biphasic structures such as H x CrS 2−δ to enable high performance in energy storage electrodes.

Zinc/bromine flow batteries are being developed for vehicular and utility load leveling applications. During charge, an aqueous zinc bromide salt is electrolyzed to zinc metal and molecular bromine. During discharge, the zinc and bromine react to again form the zinc bromide salt. One serious disadvantage of the microporous separators presently used in the zinc/bromine battery is that modest amounts of bromine and negatively charged bromine moieties permeate through these materials and react with the zinc anode. This results in partial self-discharge of the battery and low coulombic efficiencies. Our approach to this problem is to impregnate the microporous separators with a soluble cationic polyelectrolyte. In laboratory screening tests a sulfonated polysulfide resin and fully fluorinated sulfonic acid polymer substantially reduced bromine permeation with only modest increases in the area resistance.

Multiple laser beams are often used in powder bed fusion to improve productivity by melting more material per unit of time than a single laser. However, improper fusional bonding between the neighboring tracks created by different lasers can affect the integrity of tracks and degrade the mechanical properties of the printed parts. Here, we apply experiments, an analytical model, and data analysis to investigate the influence of process parameters and alloy properties on the inter-track bonding for the dual-laser powder bed fusion process using stainless steel 316 and Ti6Al4V alloys. The inter-track bonding between two neighbor-deposited tracks is characterized and classified as merged or separated. We develop an inter-track bonding index, I b , as the ratio of the mean value of the two melt pools ’ widths to the hatch spacing between two lasers. When I b is greater than 1.2, it suggests that two tracks are merged. Otherwise, the two tracks are separated. This index can predict the inter-track bonding, merged or separated, with 95.5 % accuracy using two hundred independent experimental data. In addition, the Ti6Al4V alloy is more likely to get properly merged tracks compared to stainless steel 316 under the same process condition. Multiple inter-track bonding process maps are generated under various process conditions for two alloys. Both the inter-track bonding index and process maps provide easy-to-calculate and easy-to-apply methods to optimize process conditions and enhance the bonding between two neighbor-deposited tracks and the mechanical properties of the printed parts for dual-laser powder bed fusion.

In the laser powder bed fusion (LPBF) process, powders exhibit different behaviors based on process conditions and material properties. Some powders may melt and form deposits, others become partially melted and attach to the melt pool, while some may be ejected, and certain powders remain unaffected. However, only a fraction of powders ultimately undergo full melting and contribute to the formation of the final parts. Here, we define powder melting efficiency as the ratio of the deposited track mass to the mass of powder consumed. We investigate the influence of process parameters and alloy properties on powder melting efficiency using stainless steel 316 and Ti6Al4V powders. We find that with rising laser power or decreasing scanning speed, the deposited track width increases at a greater rate than that of the denudation width. Therefore, powder melting efficiency can be improved by increasing laser power or reducing scanning speed and layer thickness. Under the same process condition, Ti6Al4V alloy exhibits higher powder melting efficiency compared to stainless steel 316. Multiple powder melting efficiency maps are generated under various process conditions for two alloys. In addition, we derive a dimensionless powder melting index to represent the ratio of the volumetric energy input to the energy required to melt per unit mass powder. This well-tested dimensionless index provides the quantitative correlation among the process parameters, alloy properties, and powder melting efficiency. Both the powder melting efficiency maps and dimensionless index can help optimize process conditions for printing high-quality parts economically.

Spatially selective melting of metal materials by laser irradiation allows for the precise welding as well as the 3D printing of complex metal parts. However, the simple scanning of a conventional Gaussian beam typically results in a melt track with randomly distributed surface features due to the complex and dynamic behavior of the melt pool. In this study, the implications of utilizing a dynamically oscillating energy input on driving melt track fluctuations is investigated. Specifically, the laser intensity and/or intensity distribution is sinusoidally modulated at different scan speeds, and the effect of modulation frequency on the resulting surface features of the melt track is examined. The formation of periodically oriented surface features indicates an evident frequency coupling between the melt pool and the modulation frequency. Moreover, such a frequency coupling becomes most prominent under a specific modulation frequency, suggesting resonant behavior. The insights provided in this study will enable the development of novel methods, allowing for the control and/or mitigation of inherent fluctuations in the melt pool through laser-driven resonances.

Existing auto-focusing methods in laser processing typically include two independent modules: surface detection and z-axis adjustment. The latter is mostly implemented by mechanical z-stage motion, which is up to three orders of magnitude slower than the lateral processing speed. To alleviate this processing bottleneck, we developed a single-lens approach, using only one high-speed z-scanning optical element, to accomplish both in-situ surface detection and focus control quasi-simultaneously in a dual-beam setup. Our approach provides instantaneous surface tracking by collecting position information and executing focal control both at 140-350 kHz, which significantly accelerates the z-alignment process and offers great potential for enhancing the speed of advanced manufacturing processes in three-dimensional space.

In this work, carbonaceous structures composed of graphitic nanocrystals, namely electrically conductive turbostratic graphite or fluorescent graphene quantum dots (GQDs), were patterned on polydimethylsiloxane (PDMS) by laser-induced graphitization. By exploiting the electrical conductivity of the turbostratic graphite and the elasticity of PDMS, a small and sensitive piezoresistive pressure sensor was realized. On the other hand, by exploiting the fluorescence of GQDs and the transparency of PDMS, an anticounterfeiting security tag containing hidden information was realized. This work indicates the implications of using laser-induced graphitization towards the fabrication of novel polymer-based electrical and optical devices.

Laser direct writing of 3D carbon structures onto flexible polymer substrates offers potential of rapid roll-to-roll manufacturing for a variety of key applications, including large area sensors, flexible electronics, robotics, energy storage/conversion, and other consumer applications. The specific formation mechanism of the carbon structures has been an issue of debate for many years with the prevailing notion of a simple photothermal conversion reaction that mainly depends on the total energy input. However, this view has been shown to be inconsistent with experimental observations of nonlinear changes in the resulting structures when multiple processing parameters are simultaneously changed. In this study, we propose a formation mechanism based on the nucleation and growth of laser-induced defects, which is experimentally validated by irradiating a continuous wave laser beam onto polydimethylsiloxane. The model is further validated by intentionally introducing controlled defects by femtosecond laser irradiation, and indicate the implications of a two-laser laser direct writing technique to go beyond the current processing limits. These results clarify the previously ambiguous mechanisms by which carbon structures form under laser irradiation and provide a deeper understanding of how to control photo-thermal processes for advanced material processing.

Laser surface structuring has emerged as a versatile technology for precise and localized material processing. When dealing with femtosecond lasers, thermal effects and collateral damage are reduced due to nonlinear light-matter interaction, improving the processing. This study explores the fabrication of microstructures using femtosecond pulses on thin films of chalcogenide glasses, which can be used for photonics applications, such as waveguides, fiber lasers, and photonic crystals. Moreover, the photoinduced changes in chalcogenide glasses have opened up new possibilities in optoelectronics, data storage, and other applications. Femtosecond laser machining of amorphous thin films of As 2 S 3 and As 2 Se 3 using femtosecond laser pulses is investigated through various microscopy techniques and spectroscopy tools, focusing on the impact of incubation effects and controlled photo-oxidation. This research contributes to a deeper understanding of the interaction of ultrafast pulses with chalcogenide glasses, promoting further advancements in photonics and optoelectronic applications.

Today, tailored laser beams are rarely used and thus an opportunity to optimize existing or introduce new processes is missed. New methods of dynamic beam shaping have the potential to change that in future. This keynote paper deals with methods allowing a transient energy input into the workpiece at such time scales that the underlying interaction processes are guided towards the desired result. It shows principles, categorizes necessary system technology, and gives application examples to familiarize the reader with the topic. It postulates that time-scale-dependent coupling between transient energy input and addressed process features is key for achieving the optimum.

Abstract Existing auto-focusing methods in laser processing typically include two independent modules, one for surface detection and another for $$z$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>z</mml:mi> </mml:math> -axis adjustment. The latter is mostly implemented by mechanical $$z$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>z</mml:mi> </mml:math> stage motion, which is up to three orders of magnitude slower than the lateral processing speed. To alleviate this processing bottleneck, we developed a single-lens approach, using only one high-speed $$z$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>z</mml:mi> </mml:math> -scanning optical element, to accomplish both in situ surface detection and focus control quasi-simultaneously in a dual-beam setup. The probing beam scans the surface along the $$z$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>z</mml:mi> </mml:math> -axis continuously, and its reflection is detected by a set of confocal optics. Based on the temporal response of the detected signal, we have developed and experimentally demonstrated a dynamic surface detection method at 140–350 kHz, with a controlled detection range, high repeatability, and minimum linearity error of 1.10%. Sequentially, by synchronizing at a corresponding oscillation phase of the $$z$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>z</mml:mi> </mml:math> -scanning lens, the fabrication beam is directed to the probed $$z$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>z</mml:mi> </mml:math> position for precise focus alignment. Overall, our approach provides instantaneous surface tracking by collecting position information and executing focal control both at 140–350 kHz, which significantly accelerates the axial alignment process and offers great potential for enhancing the speed of advanced manufacturing processes in three-dimensional space.

The prediction of crystal properties plays a crucial role in the crystal design process. Current methods for predicting crystal properties focus on modeling crystal structures using graph neural networks (GNNs). Although GNNs are powerful, accurately modeling the complex interactions between atoms and molecules within a crystal remains a challenge. Surprisingly, predicting crystal properties from crystal text descriptions is understudied, despite the rich information and expressiveness that text data offer. One of the main reasons is the lack of publicly available data for this task. In this paper, we develop and make public a benchmark dataset (called TextEdge) that contains text descriptions of crystal structures with their properties. We then propose LLM-Prop, a method that leverages the general-purpose learning capabilities of large language models (LLMs) to predict the physical and electronic properties of crystals from their text descriptions. LLM-Prop outperforms the current state-of-the-art GNN-based crystal property predictor by about 4% in predicting band gap, 3% in classifying whether the band gap is direct or indirect, and 66% in predicting unit cell volume. LLM-Prop also outperforms a finetuned MatBERT, a domain-specific pre-trained BERT model, despite having 3 times fewer parameters. Our empirical results may highlight the current inability of GNNs to capture information pertaining to space group symmetry and Wyckoff sites for accurate crystal property prediction.

Complex fibrillar networks mediate liquid-liquid phase separation of biomolecular condensates within the cell. Mechanical interactions between these condensates and the surrounding networks are increasingly implicated in the physiology of the condensates and yet, the physical principles underlying phase separation within intracellular media remain poorly understood. Here, we elucidate the dynamics and mechanics of liquid-liquid phase separation within fibrillar networks by condensing oil droplets within biopolymer gels. We find that condensates constrained within the network pore space grow in abrupt temporal bursts. The subsequent restructuring of condensates and concomitant network deformation is contingent on the fracture of network fibrils, which is determined by a competition between condensate capillarity and network strength. As a synthetic analog to intracellular phase separation, these results further our understanding of the mechanical interactions between biomolecular condensates and fibrillar networks in the cell.

Hydrogels are compelling materials for emerging applications including soft robotics and autonomous sensing. Mechanical stability over an extensive range of environmental conditions and considerations of sustainability, both environmentally benign processing and end-of-life use, are enduring challenges. To make progress on these challenges, we designed a dehydration-hydration approach to transform soft and weak hydrogels into tough and recyclable supramolecular phase-separated gels (PSGs) using water as the only solvent. The dehydration-hydration approach led to phase separation and the formation of domains consisting of strong polymer-polymer interactions that are critical for forming PSGs. The phase-separated segments acted as robust, physical cross-links to strengthen PSGs, which exhibited enhanced toughness and stretchability in its fully swollen state. PSGs are not prone to overswelling or severe shrinkage in wet conditions and show environmental tolerance in harsh conditions, e.g., solutions with pH between 1 and 14. Finally, we demonstrate the use of PSGs as strain sensors in air and aqueous environments.