The enabling technology is direct ink writing, an extrusion-based form of 3D printing in which a viscous ink is pushed through a fine nozzle along programmable toolpaths, building up complex three-dimensional structures layer by layer. What makes this work distinctive is not the printer itself but the inks. The researchers formulated soft polymer matrices loaded with two kinds of functional magnetic particles. Neodymium-iron-boron, or NdFeB, particles provide the strong, permanent magnetization that lets an external field push and pull on the robot’s limbs. Iron oxide, Fe3O4, particles play a subtler role: they concentrate heat locally when the material is exposed to a rapidly oscillating magnetic field. By printing these two particle-laden inks alongside plain soft polymer into a single monolithic architecture, the team created a robot in which actuation, heating, and structural compliance are distributed exactly where they are needed.

The cleverness of the design lies in how the two particle systems divide the labor. When a high-frequency magnetic field is applied, the Fe3O4 particles act as microscopic heaters, warming only the regions where they were printed. Those regions are made of shape memory polymers, materials that soften dramatically above a transition temperature and then stiffen again on cooling, remembering whatever shape they were molded into while soft. By selectively heating different zones of the robot, the operators can temporarily reduce the stiffness of specific parts of the body, allowing the low-frequency magnetic field that simultaneously drives the NdFeB-rich segments to fold or twist the robot into a new geometry. Once the high-frequency field is switched off, the shape memory polymer cools and hardens, locking the new shape in place without any continuous power input.

This combination of on-demand softening and magnetic reshaping is what the authors describe as on-the-fly shape morphing, and the phrase is meant literally. The robot does not need to stop, be picked up, or be reprogrammed between modes. While it is mid-crawl, an operator can ramp up the high-frequency field, watch a segment of the body go limp and refold under the steering field, then drop the frequency and the robot resumes locomotion in its new configuration, for example switching from a crawling posture suited to squeezing through a narrow channel to a compact rolling form suited to open ground. Because the entire body is one printed piece, there are no hinges, screws, or assemblies to fail, and the shape transition is reversible and repeatable.

Demonstrating robust locomotion was a central part of the study. The team showed the robot transitioning among at least three distinct gaits: crawling, in which the body deforms cyclically to generate friction-anchored forward motion; rolling, in which the locked body shape lets the field tumble the robot efficiently across flat terrain; and jumping, in which stored elastic energy is released in a rapid burst to hop over obstacles. Each mode places different demands on the body’s stiffness and geometry, which is precisely why the ability to reconfigure matters. A robot locked into a crawler’s elongated profile cannot roll well, and a roller cannot leap. The printed architecture lets one physical object embody all three, selected in real time by external fields alone.

The researchers also demonstrated environmental adaptation and targeted load-bearing delivery, pushing the robot across multiple terrain types and showing that it could carry a payload to a designated location. This is where the work connects to some of the most pressing applications in soft robotics. Machines that must operate in unstructured and confined environments, such as the inside of industrial piping, disaster rubble, or the digestive tract, face constantly changing conditions. A rigid robot tuned for one environment fails in another. A soft robot that can flatten to pass a constriction, then roll briskly across an open chamber, then hop over a lip, addresses that variability with a single, untethered platform driven only by fields that penetrate deeply into the body without wires or batteries.

The significance of the non-contact aspect deserves emphasis. Many shape-changing robots rely on embedded heaters, pneumatic channels, or cables to trigger reconfiguration, all of which require either tethering to external equipment or complex onboard hardware. The Jilin-led team’s approach uses only magnetic fields, which pass through the material without physical connection. High-frequency fields for heating and low-frequency fields for actuation can be generated by external coil systems, meaning the robot itself carries no electronics at all. That simplicity translates into durability and miniaturization potential, since there is nothing onboard to break, seal, or power, and it opens a path toward robots small enough for biomedical use where batteries and wiring are impractical.

From a materials science standpoint, the study also showcases how direct ink writing expands design freedom in soft robotics. Conventional soft robot fabrication, often based on molding and soft lithography, struggles to place multiple functional materials with fine spatial control inside a single compliant body. Extrusion printing solves this by letting the designer choose, voxel by voxel along each printed line, whether a given region is elastic, magnetically responsive, or heat-generating, and how the magnetization directions and particle concentrations are graded across the structure. The result is a dual polymer matrix architecture in which mechanics and function are co-designed, a philosophy increasingly seen as the future of multifunctional soft machines. The monolithic multi-material body also avoids delamination failure modes that plague glued or bonded assemblies of dissimilar soft materials.

The work was carried out at the Key Laboratory of Bionic Engineering of the Ministry of Education at Jilin University, with Yumeng Han, Lu Zhang, and Xueli Zhou contributing equally as lead authors, alongside Qingping Liu, Luquan Ren, Chao Xu, and Liang He of the Institute of Biomedical Engineering at the University of Oxford. The research was supported by the National Natural Science Foundation of China, the Department of Science and Technology of Jilin Province, and the 10th CAST Young Elite Scientists Sponsorship Program. The team reports no competing interests, and the article is published open access, with extensive supplementary video material documenting the robot’s crawling, rolling, jumping, and payload-carrying maneuvers.

What comes next is the question that inevitably follows a demonstration like this. The dual-field magnetic strategy scales conceptually to smaller length scales, where magnetic actuation is already the method of choice for millimeter-scale medical robots, and the shape memory locking mechanism solves one of the field’s chronic problems, which is that soft robots typically need continuous field input merely to hold a pose. If future versions can reconfigure among even more modes, sense their surroundings, and do so at clinical scales, the printed morphing body demonstrated here could become a blueprint for a generation of untethered machines that change their bodies the way animals do, adapting their form to the task at hand while never stopping to make the change.

Subject of Research: Direct ink writing of multi-material soft polymer matrices for magnetically actuated, shape-morphing soft robots

Article Title: Direct ink writing of soft polymer matrices enables on-the-fly shape morphing in soft robots

Article References: Han, Y., Zhang, L., Zhou, X., Liu, Q., Ren, L., Xu, C., & He, L. (2026). Direct ink writing of soft polymer matrices enables on-the-fly shape morphing in soft robots. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02078-x

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02078-x

Keywords: soft robotics, direct ink writing, shape memory polymers, magnetic actuation, NdFeB particles, Fe3O4 particles, shape morphing, dual magnetic fields, multi-material 3D printing, locomotion modes, bioinspired robotics, smart materials

The problem the Allstruder addresses is well known to anyone working in bioprinting, food printing, soft robotics, or electronics fabrication. Commercial extrusion systems generally fall into two camps, each with a fundamental compromise. Volumetrically accurate syringe pumps deliver precise doses but respond sluggishly, while pressure-based syringe extruders build pressure quickly but sacrifice precision. Both categories tend to be expensive, difficult to customize, and poorly matched to the open, modular workflows that dominate academic and educational settings. The result, the authors argue, is a technical barrier that drives labs to build in-house hardware for the same unmet need over and over, undermining reproducibility and accessibility across the community. A graduate student, they note, should not have to spend months developing a bespoke extruder simply to print a new bioink.

The do-it-yourself landscape has not solved this fragmentation. The rise of affordable desktop thermoplastic printers has inspired dozens of creative open-source fluid extrusion designs, but nearly all are tailored to specific materials, machines, or niches, and few generalize across use cases, users, and environments. Labs frequently tailor their workflows to the constraints of a particular extruder, locking themselves into siloed methodologies that limit interoperability and shared progress. Several prior designs nonetheless stand out as foundational. The Replistruder series brought affordable, precise, retractable syringe extrusion to embedded FRESH bioprinting and became the most widely cited and remixed open extruder family, with the Replistruder 3 setting benchmarks for accessibility, the Replistruder 4 adding off-the-shelf metal parts for reliability, and the Replistruder 5 pushing toward high-performance, multi-material use. The Large Volume Extruder handled 50 mL syringes for bulkier pastes such as clays, the Enderstruder converted the ubiquitous Creality Ender 3 into a capable fluid printer at minimal cost, and the pioneering Fab@Home platforms introduced early direct ink writing and extruder retraction concepts.

To evaluate these predecessors systematically, the team developed a five-metric framework covering affordability, performance, simplicity, versatility, and design for 3D printing, decomposing each metric into measurable sub-criteria and scoring every device against them. The published rubric reveals a pattern of deliberate trade-offs rather than failures. The Replistruder 3 scored well on affordability and performance but poorly on simplicity because it demanded considerable expertise. The Replistruder 4 traded fully printed construction for the stiffness of aluminum and steel, gaining performance while preserving accessibility. The Replistruder 5 ranks highest in mechanical performance because it is optimized entirely around premium glass syringes and a narrow, high-quality configuration, which is precisely why it scores lower on versatility and affordability. The Enderstruder maximizes simplicity for a single popular printer, while the Large Volume Extruder accepts a resolution ceiling in exchange for large volumes of low-cost material. No prior tool, the analysis shows, occupies the center of the design space.

The Allstruder was engineered to do exactly that: remain broadly capable across all five metrics simultaneously, with particular attention to the simplicity and versatility gaps left by existing designs. Mechanically, it divides into four main sections. The actuator consists of a 3D-printed frame housing a leadscrew-driven pusher block guided along a precision linear rail, with the leadscrew supported by ball bearings at both ends for smooth, stable motion. Two frame sizes offer stroke lengths of 66 and 116 millimeters. The transmission, housed in a printed motor mount, uses a fiber-backed 2GT timing belt to couple a NEMA 14 or NEMA 17 stepper motor to the leadscrew, with slotted mounting holes allowing straightforward belt tensioning and backlash reduction. A keyed slot on the pusher block mates with a boss on each syringe adapter, guaranteeing correct realignment every time a syringe is swapped.

That adapter system is the heart of the device’s material and machine agnosticism. Paired printed adapters, one gripping the syringe plunger and one holding the barrel, allow the Allstruder to accept reusable gastight glass syringes from 0.1 to 25 mL and disposable plastic syringes from 3 to 100 mL, positioning each syringe as close as possible to the actuator to minimize deflection and positional error. The growing component ecosystem includes two frames, two motor mounts, two pusher blocks, twelve syringe adapters, a Bowden nozzle adapter, a syringe heater for materials like chocolate, and more than ten printer mounts. Three example configurations illustrate the range: a balanced base setup with a 2.5 mL glass syringe; a large-volume Bowden arrangement using a 50 mL syringe and extended frame, mounted to the printer frame with extrusion delivered through tubing; and an extreme-precision build pairing a 0.1 mL glass syringe with anti-backlash components and a 0.9-degree stepper motor for fine control of precious inks.

Physical design choices reflect the demands of high-speed, multi-material printing. Four widely spaced mounting bolts secure the extruder firmly to a printer’s gantry, and a deliberately low center of mass minimizes vibration and wobble from inertia during sharp directional changes, much like a wide-wheelbase racing car. The motor, the widest component, sets the overall width at roughly 44 millimeters, allowing multiple Allstruders to be arrayed densely for multi-material work or spaced apart for applications such as printing into petri dishes. The platform supports direct drive and Bowden-style setups, coaxial extrusion, high-pressure, high-resolution, and high-speed configurations. Assembly requires only metric Allen wrenches and standard bolts, proceeds largely in a single plane, and is documented in step-by-step video guides. Printed parts are optimized for PETG on standard FFF machines, refined through more than 85 iterations aimed at improving first-print success rates, with PCTG and certain photopolymer resins also validated.

Validation was conducted through a distributed network of laboratories using different materials, printers, and skill levels, with iterative feedback used to eliminate adoption-limiting issues. The device has been fitted to more than twelve popular printers and bioprinters, ranging from Creality Ender 3 V2 machines to a CellInk INKREDIBLE, and was adapted to the Printess, a low-cost open-source bioprinter from the Skylar-Scott lab, via a custom mount. Mechanically, a dial-indicator test pressurizing a 5 mL plastic syringe to 30 PSI above ambient, a pressure exceeding what most bioinks require, measured a maximum pusher deflection of just 20 micrometers at a calculated force of 24 newtons, quantifying the rigidity of the drive mechanism itself. In a representative print test on a Creality K1 SE using a 1 mL glass syringe, 23 mg/mL Type I collagen, and a 30-gauge needle, printed collagen filaments averaged 141.8 micrometers in width against a 150-micrometer needle, with center-to-center spacing errors below 3 percent and between-filament spacing errors under 4 percent, results the authors attribute largely to the host printer and syringe rather than the extruder.

Beyond printing, the team envisions the Allstruder as shared infrastructure with uses well beyond its original community. Researchers can move between embedded FRESH printing and direct ink writing across bioinks, hydrogels, ceramic and aerogel precursors, edible materials, conductive inks, and silicones on a single reconfigurable head. Hardware developers can treat it as a stable, well-characterized base for custom syringes, heaters, chillers, manifolds, active mixing heads, and valved dispensers. Labs with heterogeneous printer fleets can standardize on one extrusion platform, making protocols portable between machines and institutions. The actuator can even serve as a programmable, printer-controlled syringe pump for reagent metering or fabricating assay substrates such as immunochromatographic test strips, and it functions as a low-cost, openly documented linear stage for general precision-motion tasks. At roughly 50 dollars per unit, it has already been used in workshops worldwide where commercial syringe-extrusion systems would be cost-prohibitive, lowering the barrier to hands-on education in additive manufacturing and biofabrication.

The Allstruder’s release arrives amid growing calls for standardization in extrusion-based bioprinting, where round-robin studies have highlighted how difficult reproducibility remains across labs. By consolidating lessons from a decade of open-source extruder development into one adaptable, rigorously characterized platform, its creators hope to shift community effort away from reinventing actuation and toward the science the hardware enables. The device does not outperform a purpose-built tool within that tool’s own niche, the authors are careful to note, but it delivers strong performance while remaining easier to use and more broadly compatible, making it the more practical option for most users and applications. In that balance, a mechanism rigid enough that print fidelity is limited only by the user’s choice of syringe and printer, offered freely and inexpensively, the Allstruder aims to become the common foundation for the next generation of syringe-based printing.

Subject of Research: An open-source, low-cost syringe pump extruder enabling versatile fluid and biomaterial 3D printing on standard desktop printers.

Article Title: The Allstruder: an open syringe extruder for every 3D printer

Article References: Hinton, T., Patten, R., PereiraTavares, A. J., Crosby, C., & Shiwarski, D. J. (2026). The Allstruder: an open syringe extruder for every 3D printer. HardwareX, 28, Article e00827. https://doi.org/10.1016/j.ohx.2026.e00827

Image Credits: AI Generated

DOI: 10.1016/j.ohx.2026.e00827

Keywords: open-source hardware, syringe extruder, 3D bioprinting, FRESH printing, direct ink writing, bioinks, additive manufacturing, HardwareX, hydrogels, low-cost bioprinter, reproducibility, CERN OHL

Conventional approaches have struggled to deliver both complex 3D geometries and arbitrary magnetization simultaneously. Uniform post-process magnetization with strong impulse fields produces only one-dimensional profiles, while techniques that deform and fix structures before magnetizing are restricted to thin, simple shapes. Direct ink writing with fields applied at the printing tip confines magnetization to the print path, making out-of-plane magnetization of curved shells difficult. Free magnets positioned beneath the substrate lose strength with height, limiting designs to flat geometries such as hinges. The new method sidesteps these constraints by positioning the magnet above the print and synchronizing magnetization with curing kinetics.

The researchers characterized the magnetic, rheological, and mechanical properties of their NdFeB-silicone composites across particle loadings of 10 to 50 weight percent. Coercivity remained essentially constant with increasing particle content, while saturation magnetization rose, allowing designers to tune magnetic response without stronger actuating fields. A 40 weight percent formulation was selected to maximize magnetic output while preserving print resolution of roughly 50 to 100 micrometers and material flexibility near 10 megapascals. Curing experiments at temperatures from 40 to 70 degrees Celsius revealed that a bed temperature of 60 degrees Celsius, yielding a nine-minute cure, best aligned cross-linking with the magnetization time scale.

A key finding is that magnetizing the composite before full curing produces stronger net magnetization than magnetizing after cross-linking. Hysteresis measurements during curing showed that magnetic domains align more readily in low-viscosity, uncured material. Thin composites magnetized prior to curing exhibited significantly larger bending angles under an external field than identical samples magnetized three hours later. Cylindrical samples magnetized from above between layers showed top-surface magnetic fields approximately 6.2 times greater than those magnetized conventionally from below, because the magnet-to-layer distance stayed constant throughout fabrication.

Bringing a magnet close to uncured, low-viscosity elastomer risks deforming the material, so the team carefully parameterized the process. They measured the minimum distance at which droplets of varying sizes remain stable without jumping toward the magnet and found that jumping propensity decreases sharply as curing progresses; after 150 seconds at 50 degrees Celsius, jumping distance fell by 76 percent. Theoretical models of bulk fluid jumping, particle migration, and particle rotation, combined with finite element analysis and X-ray fluorescence and micro-CT imaging, confirmed that magnetization under optimized conditions arises primarily from rotational alignment of particles and their magnetic domains rather than from particle migration or bulk deformation.

With the process optimized, the researchers demonstrated discretely magnetized structures, including thin strips magnetized in two regions with different directions, producing distinct bending patterns that matched finite element predictions. A cubic shell magnetized with each face oriented normal to its surface underwent competing wall deformations under external fields applied along different axes. The team also printed magnetized cubes and flexible meshes that functioned as strain sensors: compression, tension, and bending each produced measurable changes in stray magnetic fields detected by a three-axis Hall sensor, with stable responses over 2000 cycles. A flexible keycard containing sixteen independently magnetized pixels generated unique field signatures that triggered distinct LED patterns, illustrating contactless magnetic identification.

Continuous magnetization profiles were achieved by sweeping a rotating magnet along strips during curing. A single full rotation produced a strip with a single central attractive bulge, while 1.5 rotations created simultaneous regions of attraction and repulsion at one-third and two-thirds of the strip length. Hall sensor scans of the magnetization profiles closely matched simulations. Applying the same principle to a planar flower with radially symmetric quarter-rotation magnetization per petal produced S-shaped folding under an external field, a bending pattern unattainable with uniform magnetization.

Biologically inspired demonstrators highlighted the platform’s versatility. A two-centimeter dragonfly with oppositely magnetized wings flapped with maximum arc length near a 7-hertz resonant driving frequency, with finite element analysis predicting resonant modes of about 6.83 and 6.32 hertz for the front and rear wings. A neutrally buoyant robotic octopus with eight continuously magnetized arms swam vertically at up to 10.4 millimeters per second near a 4-hertz resonance in a weak 1 to 10 millitesla alternating field, and glided laterally across the water surface at 17.4 millimeters per second under a 2-millitesla static field, using a trapped air bubble for buoyancy.

The most application-oriented demonstration was a hollow serpentine catheter, 20 centimeters long, with six discrete magnetic nodes each offering two rotational degrees of freedom. Because the structure is hollow, multi-material, non-planar, and requires magnetization along the cylinder axis, it could not be fabricated by molding, print-direction magnetization, or substrate-mounted magnets. In a mock bifurcated tissue environment, the catheter was steered magnetically through tortuous pathways while self-lubricating with dyed fluid and delivering a red-dye payload to a target, mimicking minimally invasive drug delivery compatible with robotic magnetic navigation systems used clinically.

The authors note that they deliberately avoided a strong saturating pre-treatment field to isolate the effect of rotational alignment with a small cylindrical magnet, and that synergy between pre-treatment and in-process magnetization remains to be explored. Nonetheless, the framework establishes a robust route to soft, magnetically controlled actuators and sensors with tunable, programmable behaviors, opening possibilities for soft robotics, adaptive structures, shape-morphing devices, and biologically inspired magnetic systems.

Subject of Research: In-process magnetization during 3D printing of magnetorheological elastomers for heterogeneous magnetic profiles and anisotropic actuation

Article Title: In‐Process Magnetization for 3D Printing of Magnetorheological Elastomer with Heterogeneous Magnetic Profile for Anisotropic Actuation

Article References: Glass, P., Hassouna, D., Epitawala Arachchige, U., Jeong, H. Y., Park, S. H., & Joung, D. (2026). In‐Process Magnetization for 3D Printing of Magnetorheological Elastomer with Heterogeneous Magnetic Profile for Anisotropic Actuation. Advanced Science, 13(50), Article e76045. https://doi.org/10.1002/advs.76045

Image Credits: AI Generated

DOI: 10.1002/advs.76045

Keywords: 3D printing, magnetorheological elastomer, in-process magnetization, soft robotics, NdFeB composites, anisotropic actuation, Hall sensor sensing, bioinspired robots, serpentine catheter, direct ink writing, magnetic domains, programmable magnetization

The review systematically summarizes recent progress across the major 3D printing technologies used for energy storage applications, including direct ink writing, electrohydrodynamic printing, fused deposition modeling, stereolithography and binder jet printing. Particular emphasis is placed on the critical role of post-processing in regulating microstructural evolution, phase stability, interfacial bonding and electron and ion transport pathways. The authors, led by Xiaowen Zheng and Qing Sun, critically discuss how key sintering parameters such as temperature, dwell time and heating rate govern densification behavior and, ultimately, electrochemical performance. They also highlight emerging strategies involving rapid sintering, high-throughput experimentation and machine-learning-assisted optimization as promising approaches to accelerate process development and improve reproducibility.

The field traces its origins to 2013, when researchers used direct ink writing to fabricate the first interdigitated lithium-ion microbattery. Since then, battery components made with fused deposition modeling, electrohydrodynamic printing, stereolithography and binder jetting have been reported in rapid succession, spanning electrodes, electrolytes, separators and current collectors. The appeal of these approaches lies in the architectural freedom they provide. Hierarchical porosity can be engineered so that macropores facilitate electrolyte infiltration, mesopores enhance ion diffusion and micropores increase accessible surface area, collectively reducing transport resistance and improving rate performance. Complex geometries such as interdigitated, lattice and honeycomb structures can shorten ion transport pathways, while multi-material printing allows electrodes, electrolytes and current collectors to be integrated monolithically, minimizing interfacial contact resistance.

Yet the review stresses a fundamental mismatch: 3D printing primarily addresses spatial shaping rather than imparting electrochemical functionality. Electrochemical reactions and charge carrier transport occur at the nanoscale to microscale, far below the manufacturing resolution of most printing techniques. Printed green bodies generally exhibit high porosity, low density, substantial organic binders or photocurable resins, and insufficient interlayer bonding. Consequently, their electronic conductivity, ionic transport capability and mechanical strength often fail to meet the demands of battery applications. Among post-processing techniques, sintering is singled out as the most critical step, determining not only final densification and grain morphology but also the quality of interlayer adhesion, the evolution of porosity and the continuity of electronic and ionic transport pathways.

Each printing technique imposes its own post-processing requirements. Direct ink writing, the most widely applied and material-versatile method, relies on viscoelastic inks extruded through nozzles, with successful printing demanding carefully tuned rheological properties such as yield stress, shear thinning and thixotropic behavior. Electrohydrodynamic printing applies high voltage between nozzle and substrate, forming a Taylor cone that emits filaments one to two orders of magnitude finer than the nozzle itself, enabling micrometer and sub-micrometer deposition ideal for high-resolution electrode patterns and flexible substrates. Fused deposition modeling compounds active materials with thermoplastic binders into printable filaments, while stereolithography uses ultraviolet light to crosslink photosensitive resins loaded with active particles. Binder jetting selectively deposits liquid binders onto powder beds, accommodating ceramics, metals and multiphase composites without high temperatures or energy beams.

In every case, the printed structure must be transformed through curing, debinding and sintering. Pre-curing steps such as ultraviolet curing, freeze drying and solvent evaporation provide preliminary shape fixation before high-temperature treatment. Debinding, typically conducted between 200 and 600 degrees Celsius, thermally decomposes organic binders and releases them as gases, exposing functional particles and establishing initial interparticle contacts. Solvent debinding can complement this by selectively dissolving soluble binder fractions and creating interconnected pore channels that vent gaseous decomposition products, preventing blistering, cracking or large voids. Only after these stages can high-temperature sintering promote solid-state diffusion and particle necking, forming a densified skeleton with interconnected porosity and continuous transport networks.

The review devotes detailed attention to the four core dimensions of the sintering profile. Temperature governs atomic diffusion kinetics, crystal-phase transformation, grain growth, pore elimination and grain-boundary quality. Moderate elevation improves lattice ordering in intercalation-type oxide cathodes, while solid electrolytes such as LLZO and LATP require high temperatures to eliminate secondary phases, though overheating induces lithium volatilization and secondary phases that degrade ionic conductivity. Dwell time controls how far diffusion-driven processes progress, with insufficient holding leaving carbonaceous residues and trapped gases, and excessive holding causing abnormal grain coarsening. Heating rate determines how organic decomposition and gas release unfold, with rapid heating risking blistering and delamination, and the sintering atmosphere regulates defect chemistry, oxygen vacancy concentration and phase stability, with oxygen-rich conditions shown to suppress lithium oxide loss and stabilize the fast-ion-conducting cubic garnet phase.

Rapid sintering techniques are presented as a way to balance energy consumption, dimensional stability and compatibility with thermally sensitive materials. Field-assisted sintering applies pulsed direct current to generate intense Joule heating at particle microcontacts, enabling near-theoretical densities at lower furnace temperatures and shorter dwell times while suppressing excessive grain growth. Microwave sintering converts electromagnetic energy directly into heat within the material, achieving volumetric heating with rapid temperature rise and reduced thermal stress. Laser-assisted sintering uses focused beams for localized densification with a small heat-affected zone, making it compatible with polymer substrates and flexible current collectors. Emerging ultrafast high-temperature sintering and blacklight sintering, which achieve heating in milliseconds to seconds, have so far been limited to structural ceramics but could eventually accelerate the debinding-densification of battery electrodes and electrolytes.

Looking forward, the authors argue that no universal processing window exists because temperature, dwell time and heating rate are strongly interdependent and different printing techniques and material systems exhibit markedly different sintering tolerances. They advocate a shift from empirical optimization toward mechanism-guided design, coupled with high-throughput experimentation and machine learning. Machine-learning approaches, including Bayesian optimization workflows, can extract hidden relationships between sintering parameters, material structure and performance, capturing nonlinear interactions that conventional one-factor-at-a-time analyses miss. By coupling the parallel manufacturing capability of 3D printing with data-driven modeling in a closed loop of data, model and experiment, researchers can rapidly identify optimal sintering windows that balance densification, conductivity and structural stability. The review concludes that while 3D printing provides unprecedented structural design freedom, post-processing ultimately determines whether printed architectures become stable, high-performance electrochemical devices, and that continued advances in mechanistic understanding, rapid processing and data-driven optimization will position 3D printing as a viable manufacturing paradigm for next-generation energy storage.

Subject of Research: The role of printing technologies, post-processing and sintering in fabricating functional 3D-printed energy storage devices

Article Title: From printed architectures to functional batteries: printing technologies, post-processing, and sintering

Article References: Zheng, X., Mejia-Centeno, K. V., Khan, M. D., Cabot, A., & Sun, Q. (2026). From printed architectures to functional batteries: printing technologies, post-processing, and sintering. Advanced Materials Joining, 1(1), Article 2. https://doi.org/10.1007/s44500-026-00002-3

Image Credits: AI Generated

DOI: 10.1007/s44500-026-00002-3

Keywords: 3D printing, batteries, sintering, direct ink writing, solid-state electrolytes, electrodes, additive manufacturing, debinding, machine learning, energy storage, post-processing, lithium-ion batteries

Ultra-high temperature ceramics, often abbreviated as UHTCs, are defined by their melting points, which exceed 3000 degrees Celsius. Zirconium diboride sits at the heart of this family, melting above 3200 degrees Celsius while maintaining substantial strength at temperatures where nickel-based superalloys lose all structural integrity and even silicon carbide begins to soften. The material also conducts both heat and electricity remarkably well for a ceramic, a combination of properties that makes it attractive for leading edges and nose tips of hypersonic craft, where heat must be shed quickly to prevent localized thermal failure. Yet these same qualities have historically been the source of its manufacturing difficulties.

Zirconium diboride powders are hard, refractory, and resist densification. Traditional processing relies on hot pressing or spark plasma sintering, techniques that squeeze and heat powder compacts in rigid dies. The result is dense material, but only in shapes the die allows. Machining the sintered ceramic afterward requires diamond tooling and considerable patience, and internal channels, lattices, or curved cooling passages are effectively out of reach. For engineers designing thermal protection systems, the inability to shape the material has been as limiting as the cost of making it, forcing conservative designs that overuse material and add mass exactly where mass is most penalizing.

Direct ink writing offers a fundamentally different approach. In this technique, ceramic particles are dispersed into a concentrated paste-like ink that is extruded through a fine nozzle, layer by layer, following a digital design. The trick lies in formulating an ink that flows smoothly under shear stress as it passes through the nozzle, yet solidifies immediately afterward to hold its printed shape. This shear-thinning behavior, familiar from everyday examples such as ketchup or toothpaste, depends on finely tuning the solids loading, the dispersant chemistry, and the interactions between particles in the liquid carrier. For a dense, hard powder like zirconium diboride, achieving the right rheology is a serious formulation challenge.

The new study addresses this challenge by systematically developing printable inks loaded with high fractions of zirconium diboride powder, supported by organic binders and rheology modifiers that give the extruded filaments the mechanical stiffness needed for self-supporting structures. High solids loading matters because the printed green body must survive drying and burnout of the organic phase without cracking or collapsing. Too much binder, and the part shrinks dramatically and develops defects during firing; too little, and the structure slumps under its own weight before it ever reaches the furnace. Balancing these competing requirements is the central craft of the method.

Once printed, the parts undergo a carefully staged thermal schedule. Low-temperature steps remove water and burn out organic additives, generating gases that must escape slowly to avoid blistering or fracture. Sintering then follows at temperatures high enough to fuse the particles into a coherent solid. Boride ceramics pose a specific difficulty here: covalent bonding and low self-diffusion rates make conventional pressureless sintering inefficient, so densification often requires sintering additives such as silicon carbide or metallic phases, or applied pressure. The researchers report that printed components can be consolidated to useful densities while retaining the geometric complexity imparted during printing, a result that establishes the viability of the entire processing chain from digital model to refractory ceramic part.

What makes this work compelling beyond the laboratory is the design freedom it unlocks. Hypersonic flight vehicles experience aerodynamic heating that scales steeply with speed, and their leading edges must survive repeated thermal cycling at temperatures above 2000 degrees Celsius. Sharp leading edges reduce drag but concentrate heat, and cooling them from within is one of the most promising strategies for reusable systems. Internally channeled structures in zirconium diboride, impossible to produce by hot pressing and machining, could carry coolant directly through the hottest zones of the vehicle. Similar logic applies to scramjet combustor liners, rocket nozzle throats, and heat exchanger cores for advanced propulsion concepts.

The technique also speaks to broader trends in manufacturing economics. Additive approaches reduce material waste, since powder is deposited only where needed rather than machined away from an oversized billet. They compress the path from design iteration to physical prototype, allowing engineers to test geometric variations of thermal protection components in days rather than months. And they enable graded and lattice architectures that tailor heat flow and mechanical compliance in ways monolithic ceramics cannot match. For a material class in which every kilogram matters and every degree of margin counts, those advantages compound quickly.

Significant hurdles remain before printed ultra-high temperature ceramics fly on operational vehicles. Dense, defect-free consolidation at scale is not yet routine, and the mechanical properties of printed parts must be demonstrated to match or exceed those of conventionally hot-pressed equivalents under the extreme thermal gradients of flight. Reproducibility of ink rheology from batch to batch, shrinkage control during sintering, and qualification standards for safety-critical aerospace hardware are all active fronts. Nonetheless, the demonstration that zirconium diboride can be formed into complex shapes by direct ink writing converts a long-standing materials limitation into an engineering problem of the solvable kind.

The significance of the work extends past aerospace. Zirconium diboride and its relatives are candidates for plasma-facing components in fusion devices, control rod materials in high-temperature reactors, molten salt containment, and electrodes in extreme electrochemical environments. Each of these applications rewards shapes and internal structures that traditional ceramic processing cannot deliver. As printing formulations, sintering schedules, and characterization methods mature, the family of ultra-high temperature ceramics may move from being admired for what they can withstand to being designed around what they can enable, with the nozzle of a printer replacing the diamond saw as the defining tool of the trade.

Subject of Research: Additive manufacturing of zirconium diboride-based ultra-high temperature ceramics by direct ink writing

Article Title: Direct Ink Writing of ZrB2-based ultra-high temperature ceramics

Article References: Mor, M., Gardini, D., Failla, S., Sciti, D., & Vinci, A. (2026). Direct Ink Writing of ZrB2-based ultra-high temperature ceramics. npj Advanced Manufacturing. https://doi.org/10.1038/s44334-026-00113-9

Image Credits: AI Generated

DOI: 10.1038/s44334-026-00113-9

Keywords: zirconium diboride, ultra-high temperature ceramics, direct ink writing, additive manufacturing, hypersonic vehicles, thermal protection systems, ceramic sintering, rheology, refractory materials, aerospace materials, 3D printing, advanced ceramics

The appeal of ceramics is easy to understand. Materials such as alumina, zirconia, silicon nitride, and bioactive calcium phosphates combine exceptional hardness, thermal stability, and chemical resistance with, in some formulations, genuine bioactivity. They survive in jet engine hot sections, power electronics substrates, thermal protection systems, and patient-specific orthopedic implants. Yet conventional shaping routes, including pressing, injection molding, and tape casting, falter when designers demand tortuous internal channels, triply periodic minimal surfaces, hierarchical porosity, or geometries derived directly from medical scans. Every design iteration traditionally required new tooling, inflating both cost and timeline.

Among the competing additive manufacturing technologies, direct ink writing occupies a distinctive niche. Stereolithography and digital light processing deliver fine resolution but depend on photosensitive slurries with limited solids loading and suffer from light-scattering problems. Binder jetting separates shaping from sintering but struggles with powder bed management, weak green strength, and residual porosity. Laser-based methods impose punishing thermal loads and narrow processing windows that invite cracking. Direct ink writing, by contrast, works under ambient or near-ambient conditions, requires no photochemistry or powder bed, and welcomes multi-material integration, compositional gradients, and functional fillers such as conductive carbons, catalytic particles, piezoelectric phases, and magnetic components.

The technique’s history is a study in steady accumulation. Researchers at Sandia National Laboratories first extruded high-concentration ceramic slurries with partial organic binders in 1997, laying the foundation for modern robocasting. In the early 2000s, Jennifer Lewis’s group systematically studied high-solid-loading pastes, established the principles of filament stability and interlayer adhesion, and demonstrated layer-by-layer assembly of silica-based inks into three-dimensional grids. By 2006, programmable deposition systems were fabricating ceramic microstructures with sub-100-micrometer resolution. The 2010s brought alumina, zirconia, hydroxyapatite, and graphene-based composite inks, followed by multi-material printing, functionally graded structures, and fiber-reinforced ceramic matrix composites. Since 2021, the field has entered its data-driven era, with artificial intelligence optimizing processes, digital twins simulating entire workflows, and one-step debinding-sintering routes such as microwave heating compressing production cycles.

At the heart of the technology lies a deceptively simple rheological trick. A printable ceramic ink must flow smoothly under the high shear rates of roughly 100 to 1,000 per second inside the nozzle, then instantly rebuild its internal structure after deposition to resist gravity and surface tension. This shear-thinning, yield-stress behavior is commonly captured by the Herschel-Bulkley model, where a sufficiently high yield stress keeps deposited filaments from slumping while a shear-thinning exponent between 0.3 and 0.6 allows dramatic viscosity reduction during extrusion. Oscillatory rheometry adds further criteria: the storage modulus must exceed the loss modulus at low strain to signal solid-like behavior, and thixotropic recovery times shorter than one second are considered ideal for stacking tall, unsupported features.

Formulating such inks is a balancing act across four essential ingredients: ceramic particles, binders or thickeners, dispersants, and solvents. High solids loadings of 40 to 60 percent by volume are preferred because they minimize sintering shrinkage, but excessive loading compromises dispersion stability and green strength. Bimodal particle distributions, mixing coarse micrometer-scale grains with finer submicrometer particles, fill interstitial spaces and reduce viscosity at a given loading, and studies of bimodal glass bead mixtures show they consistently extrude at higher mass flow rates than monomodal inks. Binders such as polyvinyl alcohol, methylcellulose, and the thermoresponsive copolymer Pluronic F127 impart the viscoelasticity and yield stress needed for shape retention, while dispersants stabilize particles against agglomeration, with a zeta potential exceeding plus or minus 30 millivolts generally indicating robust electrostatic stabilization. Non-oxide ceramics such as silicon carbide and silicon nitride demand even stricter control, often requiring non-aqueous solvents to prevent surface hydrolysis.

Hardware and process control translate ink design into reproducible parts. Extrusion systems come in pneumatic, screw- or piston-driven, and direct-drive varieties, each trading cost against precision and response speed; direct-drive actuators respond in under 50 milliseconds and enable programmable retraction for clean start-stop transitions. Nozzle diameters range from 50 micrometers for micro-features to several millimeters for rapid prototyping, with tapered tips reducing shear stress on particles and preventing clogging. Layer height is typically set at roughly 60 percent of the nozzle diameter to ensure interlayer bonding without excessive squeezing. Dimensionless metrics guide the process: a Bond number below one predicts stable overhangs, while the yield-capillary ratio quantifies shape retention after deposition. Environmental chambers holding temperatures between 15 and 30 degrees Celsius and humidity between 40 and 60 percent stabilize solvent evaporation and prevent nozzle drying and differential shrinkage.

Modern systems increasingly close the loop with real-time sensing. Optical cameras track filament diameter and layer alignment to about 10 micrometers, laser profilometers map surface topology and detect warping, pressure sensors flag nozzle clogging through abrupt backpressure drops, and acoustic emission sensors catch microcracks and filament slippage before they become failures. Machine learning algorithms analyzing these sensor streams can adjust extrusion rate, print speed, or nozzle height within milliseconds; in one reported study, a convolutional neural network trained on filament images reduced print errors by 87 percent in a zirconia lattice structure. Embedded printing, in which inks are extruded into self-healing support baths, further offloads anti-sagging constraints and has been validated with preceramic polymers and titanium, titanium-aluminum-carbide, and alumina inks.

Post-processing remains the most defect-prone phase of the workflow. Green bodies containing 20 to 40 percent solvent must dry gently to avoid capillary-stress cracking, sometimes requiring days of controlled humidity or solvent exchange. Debinding, the thermal decomposition of organic binders between roughly 200 and 600 degrees Celsius, often consumes 10 to 50 hours and demands slow heating ramps through critical decomposition intervals identified by thermogravimetric analysis. Sintering then densifies the part, and the choice of route matters enormously: conventional furnace sintering is cheap but slow, spark plasma sintering has pushed printed silicon carbide to 98 percent theoretical density in minutes at 2,050 degrees Celsius, microwave sintering cuts cycle times by 50 to 70 percent, and ultrafast high-temperature sintering can merge debinding and densification into a single step lasting seconds to minutes. Well-optimized dense alumina and zirconia components now reach flexural strengths of 250 to 500 megapascals, approaching conventionally sintered engineering ceramics.

The application landscape is expanding accordingly. Printed silicon carbide and silicon nitride lattices serve as heat-exchanger cores, turbine filters, and lightweight aerospace panels. Hydroxyapatite and beta-tricalcium phosphate scaffolds with hierarchical porosity above 300 micrometers promote osteointegration, and drug-releasing binder systems add therapeutic function. Piezoelectric actuators, solid oxide fuel cell electrodes with engineered tortuosity that boost efficiency by 20 to 30 percent, microchannel heat sinks, and hierarchically porous catalytic frameworks for hydrogen production and wastewater treatment all showcase the method’s breadth. Significant challenges persist, including long-term ink stability at high solids loadings, the trade-off between sub-100-micrometer resolution and throughput, multi-material compatibility, and sintering shrinkage of 15 to 25 percent that distorts geometry. But with machine-learning-guided process optimization, digital twins reporting roughly 94 percent defect-prediction accuracy in early studies, one-step sintering, and functionally graded multi-material printing on the horizon, the review’s authors conclude that direct ink writing is well on its way to becoming a foundational platform for next-generation ceramic manufacturing across aerospace, energy, electronics, and biomedicine.

Subject of Research: Direct ink writing as an additive manufacturing technique for fabricating complex ceramic components from ink formulation through industrial applications

Article Title: Direct ink writing of ceramics: from fundamentals to industrial applications

Article References: Direct ink writing of ceramics: from fundamentals to industrial applications. (n.d.). https://doi.org/10.1007/s44500-026-00001-4

Image Credits: AI Generated

DOI: 10.1007/s44500-026-00001-4

Keywords: direct ink writing, ceramics, additive manufacturing, 3D printing, rheology, sintering, ceramic inks, robocasting, biomedical scaffolds, machine learning, ceramic matrix composites, thermal materials