Programmable multiscale energy release in synergistic energetic composites with three dimensional printed architectures

Domain: biology
Published: 2026-03-27
Editorial outcome: minor_revision

Abstract
Energetic materials are central to propulsion and detonation technologies, yet their performance is often limited by poor control over energy release across multiple length and time scales. Integrating highly reactive composites with molecular explosives while maintaining structural precision remains challenging. Here we show a three dimensional printing strategy that enables programmable energetic composites by combining highly reactive metastable composite systems with a crystalline high explosive through acoustic-assisted assembly. Uniform coating and intimate interfacial contact produce dense architectures with enhanced thermal reactivity, accelerated pressurization and increased energy output under confined conditions. Printed filamentary and core–shell structures further enable multistage and geometry-dependent energy release, including sustained combustion, secondary pressurization and intense fireball formation. Laser-driven and combustion experiments reveal that the energy release characteristics can be systematically tuned by composition and architecture. This work establishes a general route to structure–performance control in energetic materials and highlights additive manufacturing as a powerful platform for designing next-generation reactive and explosive systems.

Introduction
Metastable intermolecular composites (MICs)1, 2, 3, 4 are heterogeneous mixtures of metallic fuels (e.g., Al, Mg, and Ti) and oxidizer-containing components (e.g., Fe O , CuO, and PVDF)5 that rapidly undergo exothermic reactions under external stimuli to release chemical energy. Compared with conventional monomolecular energetic materials (EMs)6, 7, MICs exhibit superior energy density and combustion performance8, 9, 10, 11. Their properties can be tailored by adjusting the composition, fuel oxygen equivalent ratio (diameter)12, and particle size of the constituents13, 14. Owing to these advantages, MICs have been widely applied in propellants15, microthrusters16, 17, microelectromechanical systems (MEMSs)18, and ignition devices19. However, the inherent characteristics of MICs lead to the formation of combustion products predominantly in solid or condensed phases (e.g., metals or metal oxides), with limited generation of gaseous species20. Because gas-phase products are critical for heat/mass transfer under turbulent conditions, this deficiency results in two-phase losses21, thereby constraining the pressure output during energy release. In contrast, typical monomolecular energetic materials that are composed of C, H, O, and N (e.g., RDX, HMX, and CL-20)22 integrate fuel (C/H) and oxidizers (O/N) within a single molecule, which enables rapid energy release that is accompanied by abundant small-molecule gaseous products. Nevertheless, their thermal output is restricted by the stored chemical energy of hydrocarbons, with inherent limitations in terms of energy density, combustion velocity, and heat release efficiency23. To address these challenges, the integration of MICs with monomolecular EMs offers a promising strategy for synergistically increasing the energy output performance of hybrid systems by leveraging their complementary advantages.

In recent years, significant efforts have been made to address the limitations of both MICs and EMs through hybrid material design. Sherif Elbasuney24 proposed that nanocomposites that combine nanothermites (e.g., Fe O /Al) with EMs (e.g., HMX) represent a promising direction for advanced high-energy materials. His work demonstrated that compared with pure HMX, Fe O /Al/HMX composites exhibit improved combustion performance, with a 53–82% increase in heat release, a 17% improvement in destructive effects, a 24–30% reduction in activation energy, and an ~13°C decrease in decomposition temperature25, 26, 27, 28. Zhu and Zhang29 integrated CL-20 with Al/CuO to fabricate CuO/Al/CL-20 composites, which exhibited more intense combustion, brighter/larger flames, and greater heat release. The Al/CuO additive reduced the decomposition activation energy of CL-20 by 18.2%, and synergistic effects ensured stable and violent combustion. McCollum et al. introduced perfluoropolyether (PFPE)30 and nitrated graphene oxide (NGO)31 into MICs to mitigate their low pressurization rates during combustion. Shen et al.32 compensated for pressure-release losses in Al-CuO systems by incorporating CL-20 particles and achieved higher peak pressure and pressurization rates in Al-CuO/CL-20. Additional studies by Zhang and Ye33 on Al/MxOy@CL-20 (M = Cu, Mo) composites revealed that CL-20 doping increased both thermal output and electrostatic discharge safety. Shen34 reported that compared with Al/CuO, AP/Al/CuO composites delivered 2.7× greater specific impulse and 1.4× greater heat release. Luo et al.35 reported that Al/Fe O increased the initial burning rate of Al/Fe O /RDX, whereas RDX increased its maximum combustion velocity.

The increased reactivity of hybrid systems combining MICs with EMs has been demonstrated from various perspectives in previous studies36. However, in these works, primarily simple physical mixing methods were employed, thus leaving the underlying synergistic energy-release mechanisms unexplored. Crucially, whether an optimal formulation ratio exists for maximizing energy density by spatially optimizing the MIC–EM configuration remains unclear. Beyond mixing ratios, the packing architecture of MICs and EMs plays a pivotal role in controlling energy release. Recent research has focused solely on microscopic particle interactions, and macroscopic structural design as a means for regulating performance has been neglected. Although MICs exhibit higher energy density than EMs do, their slower reaction kinetics—owing to heterogeneous combustion—limit detonation velocities. Thus, designing macrostructural configurations that match the dynamics of energy propagation is essential for achieving ideal energy-release profiles. The primary challenge in realizing such structurally tailored composites lies in manufacturing complexity. Conventional methods lack the flexibility and efficiency required for fabricating energetics with specialized architectures. Additive manufacturing (3D printing)37, which is a layer-by-layer fabrication technique, has emerged as a transformative solution.

In terms of energetic material patterning and fabrication38, 39, 40, 41, 42, 3D printing offers unparalleled advantages, such as customizable structures, high flexibility, increased safety, and low cost43, 44, 45—thus earning its reputation as the “21st century’s most promising technology” for energetics. However, owing to the particular temperature, mechanical (impact, friction, etc.), and electrostatic sensitivity of energetic materials, potential safety hazards exist during the 3D printing manufacturing process. Direct ink writing (DIW) technology has the advantages of simple operation, high efficiency, and high safety.

In this study, heterogeneous structured EM–MIC composite 3D samples in simple and conventional environments are safely formed via the DIW technique. By leveraging the synergistic effects between MICs and EMs and using DIW 3D printing to precisely control their spatial distribution, we aim to advance the design of hybrid composites with tuneable energy outputs and optimized performance in this study.

In this study, the metastable intermolecular composite Al/Ti/CuO (ATC)46 is integrated with the conventional monomolecular explosive HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine)47, 48 to fabricate ATC–HMX composites through an acoustic resonance-assisted preparation method, and the synergistic effects between Al/Ti/CuO and HMX are systematically investigated. Using hydroxyl-terminated polybutadiene (HTPB) as a binder, we formulated printable inks and achieved three-dimensional structural control of ATC–HMX via additive manufacturing technology. The microstructures, chemical compositions, pressure outputs, and thermal release properties of the composites were comprehensively characterized, and experimental investigations were conducted to evaluate thermal reactivity, fast laser ignition characteristics, combustion performance, and energy release behaviour. In this work, we aim to establish a fundamental understanding of MIC–EM hybrid systems from both formulation design (composition optimization) and structural engineering (packing architecture) perspectives to provide new insights for the development of advanced energetic materials with tuneable energy-release characteristics.

Results
Microstructure and Composition of ATC-HMX Composite Particles
An ATC–HMX composite particle was prepared using the ultrasonic resonance technique (Fig. 1a). As shown in Supplementary Fig. 1a and b, the Al/Ti/CuO composite particles display a characteristic “lychee-like” core–shell structure (see our previous work46), whereas HMX appears as bulky crystals with micron-scale particle sizes. SEM–EDS analysis of the ATC–HMX composites (Fig. 1b and Supplementary Fig. 1c–e) revealed that the fine Al, Ti, and CuO particles together with the preformed Al/Ti/CuO composites adhered to and encapsulated the large HMX crystals, thereby resulting in the formation of an effective coating architecture. Specifically, Supplementary Fig. 1c shows considerable HMX surface exposure with minimal MIC coverage, whereas Supplementary Fig. 1d shows increased MICs but incomplete HMX encapsulation. Supplementary Fig. 1e reveals MIC aggregation with excessive coating beyond the HMX surfaces. The most uniform distribution appears in Fig. 1b, where MIC particles are evenly dispersed on the HMX surfaces. SEM analysis confirms that the 40% ATC formulation achieved optimal composite uniformity (Fig. 1b–i), which is supported by EDS images that show homogeneous spatial distributions of Al, Ti, Cu, C, O, and N throughout the ATC–HMX system, thereby verifying excellent mixing homogeneity. The XRD pattern of the ATC–HMX composite particles (Supplementary Fig. 2) is a simple combination of the characteristic peaks of both Al/Ti/CuO and HMX without any new diffraction peaks, which confirms that no premature chemical reactions or alloying occurred during the composite preparation process, thus ensuring that no energy loss occurred prior to the intended application. Furthermore, the peak intensities in the XRD patterns of 20ATC–80HMX, 30ATC–70HMX, 40ATC–60HMX, and 50ATC–50HMX are strongly correlated with their respective mass ratios.

Thermal Reaction Behaviour and Processes of ATC-HMX Composite Particles
To investigate the thermal decomposition behaviour of HMX and ATC–HMX, as well as the effect of ATC on HMX decomposition, we conducted TG–DSC–FTIR–MS measurements under an argon atmosphere at a heating rate of 10°C·min-1; the results of TG–DSC are shown in Fig. 2a and b. The FTIR spectra of the gaseous products that evolved from HMX and 40ATC–60HMX are shown in Fig. 2c and d, respectively. To accurately analyse the species and evolution temperatures of the gaseous products during the entire decomposition process, we selected the IR spectra at nine characteristic temperatures for each sample on the basis of their TG curves, which corresponded to three distinct stages: predecomposition, active decomposition, and postdecomposition (Supplementary Fig. 3). The temperature-dependent ion current profiles of gases that evolved from HMX and 40ATC–60HMX are shown in Fig. 2e and f, respectively.

As shown in Fig. 2a, pure HMX underwent a β-to-δ phase transition between 179°C and 214°C (orange dashed box), followed by thermal decomposition from 220°C to 350°C. The decomposition process began with endothermic melting at ~280.17°C (cyan dashed box) and transitioned to rapid exothermic decomposition with a peak temperature of 285.17°C, which indicates a melt-mediated decomposition mechanism. In contrast, upon heating, ATC–HMX exhibited three distinct exothermic stages. The first corresponded to HMX decomposition, and two additional prolonged exothermic stages occurred between 450°C and 950°C (pink shadow), which are attributed primarily to ATC reactions, as previously reported46. The TG curves reveal initial mass loss (HMX decomposition) followed by mass gain (oxidation of Al/Ti by CuO and oxidative gaseous products from HMX decomposition). Notably, the incorporation of Al/Ti/CuO eliminated the HMX melting peak in ATC–HMX and increased the onset decomposition temperature to ~240°C. Compared with those for pure HMX, the first exothermic peak temperatures for 20ATC–80HMX, 30ATC–70HMX, 40ATC–60HMX, and 50ATC–50HMX shifted to 281.27°C, 280°C, 278.66°C, and 279.81°C (corresponding to 3.9°C, 5.17°C, 6.51°C, and 5.36°C reductions, respectively). The 40ATC–60HMX composite demonstrated the fastest decomposition rate, with initiation and completion temperatures of 278.66°C and ~283.13°C, respectively. DSC analysis revealed increased heat flow intensity for the Al/Ti/CuO reactions with increasing HMX content. These observations demonstrate that Al/Ti/CuO alters the HMX decomposition pathway from purely melt-mediated to mixed solid-phase/melt-mediated. The MICs exhibit catalytic effects on the decomposition of EMs49, 50, 51, where thermite reaction products (TiO₂52 and Cu53) catalyse HMX decomposition and modulate heat release. Importantly, the early exothermic decomposition of HMX (220°C–350°C) provides both thermal energy and reactive gaseous products that subsequently activate Al/Ti/CuO MIC reactions (400°C–1000°C). As shown in Fig. 2b, pure HMX exhibited a rapid mass loss of 99.06% within a narrow temperature range, which indicated near-complete decomposition through a fast melt-mediated process. In contrast, the mass loss percentages of the ATC–HMX composites progressively decreased: 78.12% for 20ATC–80HMX, 69.58% for 30ATC–70HMX, 57.50% for 40ATC–60HMX, and 49.13% for 50ATC–50HMX. This systematic reduction originated from the dual-phase behaviour of Al/Ti/CuO additives: (1) During the primary decomposition stage (240–340°C), the MICs accelerated HMX decomposition kinetics without participating in the reaction; (2) in the 450–950°C range (pink shadow, Fig. 2a), the Al/Ti/CuO underwent sustained redox reactions activated by thermal energy that was released from HMX decomposition, thereby generating additional exothermic output.

A comparative analysis of the data from Fig. 2c, d and Supplementary Fig. 3 reveals distinct differences in thermal decomposition characteristics between HMX and 40ATC–60HMX. For pure HMX, exothermic decomposition initiated at relatively higher temperatures, with only CO (2360 cm-1 and 667 cm-1) and NO (1593–1635 cm-1) detected at 180°C. The complete profile of primary decomposition products, including CO (2140–2250 cm-1), CH₂O (2814 cm-1 and 1746 cm-1), N O (2237 cm-1 and 1260–1300 cm-1), NO (1965–1762 cm-1), HCN (713 cm-1), and H O (3490 cm-1)54, emerged only above 240°C. In marked contrast, 40ATC–60HMX exhibited significantly accelerated decomposition kinetics. Initial decomposition products, including NO (1593–1635 cm-1)55, CO, NO, N O (2237 cm-1), and H O (1518.7 cm-1), were already detectable at 180°C, followed by CH O signatures at 200°C and CO (2360 cm-1) at 240°C56. Notably, despite HMX being a polynitro compound, only weak NO signals appeared during the early decomposition stage (180–220°C)57, which was attributable to rapid secondary reactions between highly oxidative NO and reactive Al/Ti components.

The comparative temperature profiles in Supplementary Fig. 3 demonstrate the systematic advancement of all the decomposition product signatures in 40ATC–60HMX relative to those in pure HMX. These observations provide conclusive evidence that the Al/Ti/CuO composite effectively catalyses the thermal decomposition of HMX by (1) lowering the activation barrier for initial bond cleavage and (2) facilitating the rapid consumption of reactive intermediates via secondary redox reactions.

Mass spectrometric analysis of HMX (Fig. 2e) revealed major ion fragments with m/z ratios of 18, 27, 28, 29, 30, and 44, which corresponded to gaseous decomposition products H O, HCN, CO/N , CHO, CH O/NO, and CO /N O, respectively. In contrast, the 40ATC–60HMX composite contained predominant fragments of H O (m/z=18), CO/N (m/z=28), CHO (m/z=29), CH O/NO (m/z=30), and CO /N O (m/z=44), with nearly undetectable HCN signals. This distinct fragmentation pattern suggests that the C–N and N–N bond cleavage mechanisms differ between HMX and its composite. Notably, while NO (m/z=46) and HNCO (m/z=43) have been reported as major HMX decomposition products58, their characteristic peaks were absent in our measurements. This observation may be attributable to secondary reactions during HMX decomposition59, 60, which could have consumed these intermediate species through subsequent chemical processes. A comparative analysis of the ion current intensity profiles in Fig. 2e and f revealed that gaseous product fragments were detected at 260°C for 40ATC–60HMX, which is significantly lower than the 277°C that was required for pure HMX (see magnified insets). This temperature reduction indicates that the Al/Ti/CuO components in 40ATC–60HMX lower the exothermic decomposition temperature of HMX and accelerate the reaction kinetics. Notably, no characteristic peaks were observed for NO (m/z=46), HNCO (m/z=43), or HCN (m/z=27), which indicates that the additives promote the rapid consumption of these species through secondary reactions. The integration of mass spectrometry and FTIR data revealed CH O/NO (m/z = 30), CO /N O (m/z = 44), and CO (m/z=28) to be the primary decomposition products for HMX, whereas 40ATC–60HMX predominantly yielded CH O/NO (m/z=30) and CO /N O (m/z=44). This product distribution shift confirms the catalytic role of Al/Ti/CuO in modifying the decomposition pathways.

Combustion Performance of ATC-HMX Composite Particles in Closed, Open, and Geometrically Confined Systems
The combustion sequences of pure HMX and Al/Ti/CuO are presented in Supplementary Fig. 4a and b, respectively. The combustion process of the ATC–HMX composites is shown in Fig. 3a. The flame temperature distributions at specific moments during the combustion of ATC–HMX, which were obtained through infrared thermography, are shown in Fig. 3b. For comparative analysis, the temperature–time curve in the continuous infrared image of the sample combustion process is shown in Fig. 3c. Additionally, the durations of various temperature ranges on the combustion temperature curves (Fig. 3c) were statistically analysed, and the results are shown in Supplementary Fig. 5.

As shown in Fig. 3a and b, all the ATC–HMX powder samples with different ratios were successfully ignited and achieved self-sustaining stable combustion; bright flames were emitted, and stable combustion behaviour was demonstrated. The time to reach the maximum flame height was 475 ms for both 20ATC–80HMX and 30ATC–70HMX, whereas it was 375 ms for both 40ATC–60HMX and 50ATC–50HMX. However, compared with 50ATC–50HMX, 40ATC–60HMX maintained stable flames within the 375–475 ms range, and it exhibited a “constant combustion zone” (375 ms–475 ms) and showed slower flame decay in the later stages of combustion, which resulted in a longer duration. The combustion dynamics of the 40ATC–60HMX powder under open unconfined conditions are presented in detail in Supplementary Movie 1. As the Al/Ti/CuO content increased, the ATC–HMX samples exhibited more intense combustion reactions in the early stage (before reaching the maximum flame height) and higher flame temperatures (Fig. 3b and c), which is attributed mainly to the high calorific value of the Al/Ti/CuO combustion reaction. Although 50ATC-50HMX showed the most intense combustion and highest flame temperatures in the early stage, its flame morphology and temperature curve fluctuated, which indicated unstable combustion. In the later stage, its flame decayed the fastest. The reasons are that the higher Al/Ti/CuO content in 50ATC-50HMX led to dominant condensed-phase reactions, thereby resulting in the production of more condensed combustion products, which accelerated flame decay and extinction. Additionally, the “microexplosions” of ejected Al/Ti/CuO composite particles during combustion caused flame flickering, which resulted in unstable fluctuations. In summary, 40ATC-60HMX exhibited relatively intense combustion reactions, the most stable overall flame behaviour, and the slowest decay. But pure HMX powder could not be ignited by laser irradiation. Only a small laser spot is observed, which neither expands nor moves with time (Supplementary Fig. 4a). In contrast, the Al/Ti/CuO MICs were successfully ignited by the laser, which resulted in intense combustion that was characterized by spark ejection into the air and a phenomenon that resembled deflagration46, and this process was accompanied by a distinct crackling sound similar to that of firecrackers, as shown in Supplementary Fig. 4b. The combustion dynamics of the Al/Ti/CuO powder are presented in detail in Supplementary Movie 2. The statistical results in Fig. 3c and Supplementary Fig. 5 reveal that 40ATC-60HMX had the longest duration above the three temperature thresholds of 1000°C, 1276.25°C, and 1778.75°C (0.498 s, 0.483 s, and 0.251 s, respectively), followed by 50ATC-50HMX.

The pressure evolution processes of various samples are shown in Fig. 3d, and the corresponding peak pressures and pressurization rates are shown in Fig. 3e. The heat release of the samples at atmospheric pressure is shown by the pink dotted line in Fig. 3e. As shown in Fig. 3d and e, when ATC–HMX was ignited in a confined system, the pressure rapidly increased until it reached the peak pressure (P ), after which it gradually decreased. In contrast, pure HMX exhibited a slower pressure increase rate, which indicated a distinct “stepwise pressure increase stage” during the early combustion phase, followed by a “pressure increase deceleration zone” near P . Pure HMX had the lowest peak pressure (67.10 kPa) and pressurization rate (53.78 kPa/s). With the incorporation of Al/Ti/CuO, both the peak pressure and pressurization rate of ATC–HMX increased significantly and were positively correlated with the Al/Ti/CuO content. The P and pressurization rates of the ATC–HMX systems decreased in the following order: 50ATC–50HMX > 40ATC–60HMX > 30ATC–70HMX > 20ATC–80HMX. Notably, 50ATC–50HMX achieved the highest values (107.66 kPa and 1248.20 kPa/s), which represented improvements of 60.45% and 2220.94% over pure HMX, respectively. These improvements stemmed primarily from the rapid combustion and high exothermicity of Al/Ti/CuO, which heated the confined air and amplifies the overall pressure. Additionally, the size of the “pressure increase deceleration zone” near P decreased progressively with increasing Al/Ti/CuO loading. For 40ATC–60HMX and 50ATC–50HMX (40–50% Al/Ti/CuO), this deceleration zone completely disappeared, which indicated accelerated pressurization near peak pressure. Under atmospheric conditions, pure HMX released 5916 J/g of heat, whereas the heat release of the ATC–HMX composites substantially increased to 6992 J/g (20ATC–80HMX), 7117 J/g (30ATC–70HMX), 7331 J/g (40ATC–60HMX), and 7251 J/g (50ATC–50HMX), which corresponded to increases of 18.19%, 20.30%, 23.92%, and 22.57%, respectively (Fig. 3e). The maximum heat release occurred for 40ATC–60HMX, which was likely because of its optimized particle compactness (Fig. 1), thereby ensuring more efficient reactions and leading to greater heat release. The DSC curve (Fig. 2a) shows that the gaseous products that were generated from the decomposition reaction of 40ATC–60HMX had the highest secondary reactivity, which could have increased the exothermicity of the Al/Ti/CuO reaction. Mechanistically, Al/Ti/CuO reacts predominantly in the condensed phase with minimal gas production. However, the high-temperature gaseous products from HMX decomposition interact with the Al/Ti/CuO particles, which catalyses their redox reactions and accelerates heat release. Concurrently, the exothermicity of Al/Ti/CuO heats the surrounding gas, which amplifies the system pressure. This synergistic feedback loop between gas-phase (HMX) and condensed-phase (Al/Ti/CuO) reactions ultimately increases both the pressure and heat release in the ATC–HMX system.

Continuous time-resolved imaging of the ATC–HMX sample combustion process in a 0.5 MPa nitrogen atmosphere are shown in Supplementary Fig. 6. SEM–EDS analysis and XRD patterns of the combustion products are presented in Supplementary Fig. 7 and 8, respectively. As shown in Supplementary Fig. 6, all the ATC–HMX composite systems with different ratios could be ignited and maintain stable self-sustained combustion in a nitrogen atmosphere at 0.5 MPa, thereby resulting in the production of stable flames. The combustion durations for 20ATC–80HMX, 30ATC–70HMX, 40ATC–60HMX, and 50ATC–50HMX were approximately 565 ms, 485 ms, 485 ms, and 325 ms, respectively. As the ATC content in the ATC–HMX system increased, the combustion intensity gradually increased, whereas the combustion duration decreased. Specifically, the intensity of combustion was positively correlated with the ATC content, whereas the duration of combustion was positively correlated with the HMX content. Additionally, compared with that in air, the combustion performance in the inert gas atmosphere was weakened. As shown in Supplementary Fig. 7, the combustion products of ATC–HMX in the 0.5 MPa nitrogen atmosphere exhibited predominantly spherical or irregular chunk-like morphologies with uniform dispersion. High-magnification SEM–EDS analysis of typical spherical products revealed the presence and distributions of Al, Ti, Cu, N, and O on their surfaces, which indicated that the spherical products were composed mainly of oxynitrides of Al, Ti, and Cu. These observations demonstrate that both the ATC and the HMX components interacted and participated in the combustion reaction process. The results shown in Supplementary Fig. 8 reveal that the combustion products of the different ATC–HMX compositions in the 0.5 MPa nitrogen atmosphere were essentially identical and consisted primarily of Cu, Al O , TiO, AlCu Ti, and AlCuTi alloys, along with residual Al and CuO.

Time-sequenced images during the combustion processes of the HMX, ATC and ATC–HMX powders within the quartz tubes are presented in Fig. 4a, b and c, respectively.

As shown in Fig. 4a, pure HMX was not ignited by the CO laser, no deflagration or self-propagating combustion was observed, and only sporadic and intermittent weak luminous spots were present. As shown in Fig. 4b（Details as shown in Supplementary Movie 3）, ATC was successfully ignited by a CO laser under geometric confinement and achieved self-propagating combustion. The reaction was rapid and vigorous and was characterized by an intense flame and the ejection of burning particles, with occasional overexposure between 1.1 ms and 2.1 ms, and even the reaction force generated by combustion injection pushes the quartz tube out. However, the entire combustion event was short lived because of its dominance by condensed-phase redox reactions. In contrast, the data in Fig. 4c demonstrate that ATC–HMX composite particles with added Al/Ti/CuO were successfully ignited by the CO laser in the quartz tube and achieved self-sustaining combustion, with flames and burning particles ejected from the tube opening. The ejected flames and burning particles maintained stable rightward propagation along the horizontal plane. Among the composites, 40ATC–60HMX had the shortest time (150 ms) for the flame to propagate to the far right, which indicated the fastest flame propagation speed, followed by 50ATC–50HMX (200 ms), 30ATC–70HMX (200 ms), and 20ATC–80HMX (250 ms). Moreover, 40ATC–60HMX exhibited more intense combustion with faster and more violent flame propagation, which was characterized by the vigorous ejection of incandescent particles, which is consistent with its combustion behaviour in open systems. Additionally, sequential snapshots of sample combustion revealed that adding Al/TIi/CuO to HMX enabled the complete deflagration-to-detonation transition (DDT) process61, which was specifically manifested as flame expansion and ejection phenomena during ATC–HMX combustion, with a shock-compressed combustion stage occurring during DDT (which was most evident in 40ATC–60HMX). The underlying reason is that the gaseous products from HMX decomposition intensified the convective mechanism in flame propagation during the combustion process, whereas the substantial heat that was generated by Al/Ti/CuO reactions improved the thermal conduction and radiation mechanisms in flame propagation. The synergistic coupling of these three mechanisms collectively intensified the DDT process in the samples62. Conversely, accelerated combustion led to pressure buildup, which resulted in the formation of stronger compression waves. The gradual accumulation of pressure caused the compression waves to develop into strong shock waves, which, upon reaching the critical intensity, triggered deflagration35. We also observed that during the combustion of ATC–HMX composite particles under geometric confinement conditions, the fine particles that were ejected from the quartz tube orifice continued to undergo secondary “microexplosion” reactions during their dispersal process, thereby intensifying the combustion reaction. The deflagration-to-detonation transition (DDT) dynamics of the 40ATC–60HMX powder under weak geometric confinement are demonstrated in detail in Supplementary Movie 4.

The ATC–HMX composite demonstrated intense yet stable combustion performance in both open and confined combustion experiments, which can be attributed to the synergistic energy release between the Al/Ti/CuO MICs and HMX. First, as previously described, Al/Ti/CuO particles adsorbed onto, encapsulated, or even filled the spaces between HMX crystals, thereby resulting in the formation of Al/Ti/CuO-coated HMX composite particles. This configuration ensured better interfacial contact between components, thereby promoting mass and heat transfer processes. Second, the components in ATC–HMX exhibited complementary effects during combustion. HMX was ignited by the substantial heat that was released from the Al/Ti/CuO thermite reactions and rapidly decomposed to generate large amounts of gas. This gas production improved the convective combustion mechanisms during flame propagation while simultaneously increasing the combustion rate of Al/Ti/CuO. Furthermore, aluminium reacted with the decomposition products of HMX63, which resulted in the release of additional heat that sustained combustion propagation. Rapid heat accumulation coupled with thermal gas expansion transitioned the system into an unstable deflagration state. In summary, the integration between Al/Ti/CuO and HMX improved both the structural and reactive characteristics of the entire energetic system. This resulted in more complete and intense combustion while maintaining relatively stable flame characteristics. The stable combustion and subsequent detonation of ATC–HMX composites can provide a continuous energy output.

Fast Dynamic Response of ATC–HMX Composite Particles to High-Energy Laser Shock
High-speed schlieren images of the fast evolution of plasma and shock waves during high-energy laser irradiation of ATC–HMX are shown in Fig. 5a, and the corresponding schlieren sequence for pure HMX is shown in Supplementary Fig. 9. On the basis of the shock wave propagation distances that were measured at different times, as shown in Fig. 5a, the corresponding velocities were calculated. The resulting shock wave velocities for different ATC–HMX samples at various times are summarized in Table 1. To quantify the energy release dynamics of ATC–HMX under laser irradiation, the propagation distances of the shock waves at various time intervals were fitted, and the results are displayed in Fig. 5b, and the detailed fitting data are provided in Supplementary Table 2. The fitting yielded correlation coefficients that exceeded 0.98, which indicated excellent agreement. The analysis revealed that the shock wave propagation distance (s) follows an exponential relationship with time (t), as expressed in Equation 1, which is consistent with the theoretical models proposed by McKay64 and Nanai65. The energy release rate of ATC–HMX directly governs the shock wave velocity; thus, the propagation speed reflects the energy supply level at each reaction stage66. By differentiating Equation 1 with respect to time (t), the time-dependent velocity of the shock wave front was derived, as shown in Equation 2. On the basis of Equation 2 and the fitting results in Supplementary Table 2, the temporal evolution of the shock wave velocity for ATC–HMX was plotted, as shown in Fig. 5c.

𝑠 = 𝑠 +𝑎𝑡𝑏 (1)
𝑣 = 𝑎𝑏𝑡𝑏−1 (2)
where s represents the propagation distance of the front of the shock wave, mm; t represents the propagation time of the shock wave, us; s , a and b represent undetermined coefficients; and v represents the propagation velocity of the front of the shock wave, mm/us.

As shown in Fig. 5a, under the impact of a high-energy laser, ATC–HMX rapidly undergoes reactions such as melting and evaporation, followed by ionization to generate plasma. The expansion pressure of the plasma compresses the surrounding air to produce shock waves that propagate outwards. Through prolonged energy transfer between vapour molecules, the energy behind the shock wave gradually becomes uniform. By 5.215 μs, the cross-section of the shock wave has formed a uniform circular shape with radius R. At 2.215 μs, intense plasma emission (white area in Fig. 5a) can be observed in the laser-impacted region of the sample. The plasma expands outwards in an ellipsoidal shape and gradually attenuates. Affected by the strong plasma emission, distinct shock waves can only be observed above the plasma region during the early stage (2.715–3.215 μs) and become more clearly visible in the later stage (3.715–5.215 μs). Furthermore, we found that a higher Al/Ti/CuO content leads to greater plasma light intensity, whereas a higher HMX content results in faster shock wave propagation. This finding indicates that ATC is more prone to ionization under the impact of a high-energy laser, and its reaction is more favourable for enhancing the temperature field, heating the gaseous products from the HMX reaction, and generating strong plasma. HMX has a lower decomposition temperature and can completely decompose at the melting and vaporization temperatures of Al/Ti/CuO, which produces large amounts of gas and heat that contribute to shock wave development. As shown in Fig. 9c, the decrease in the shock wave velocity of ATC–HMX can be divided into two stages. In the first stage (before 1 μs), the shock wave velocity decreases most rapidly. This stage represents the process in which plasma/vapour converts thermal energy into kinetic energy. With the generation and propagation of shock waves, energy is rapidly consumed, and the gas temperature behind the shock wave decreases, which results in a faster velocity reduction. In the second stage (after 1 μs), the decrease in the shock wave velocity slows because the chemical energy release from the ATC–HMX reactions partially replenishes the shock wave energy, and the temperature decrease of the ATC–HMX plasma slows67. Moreover, in Stage I, 30ATC–70HMX and 40ATC–60HMX have faster instantaneous shock wave velocities, followed by 20ATC–80HMX, whereas 50ATC–50HMX has the slowest instantaneous shock wave velocity. Within 3 μs (5.215 μs) after laser shock, the average shock wave velocities of 20ATC–80HMX, 30ATC–70HMX, 40ATC–60HMX, and 50ATC–50HMX were 1296.67 m/s, 1210 m/s, 1193.33 m/s, and 1150 m/s, respectively. For comparison, the shock wave velocity of pure HMX was 593.33 m/s within 3 μs (5.715 μs); this value was derived from Supplementary Fig. 9. A comparative analysis reveals that the shock wave velocity of ATC–HMX was 93.83%–118.55% greater than that of HMX. As the HMX content decreases, the average shock wave velocity of ATC–HMX gradually decreases. The plasma/shock wave dichotomy suggests that ATCs dominate early-stage energy release, whereas HMX governs wave propagation. The increased laser-induced plasma intensity that was observed with Al/Ti/CuO originates from the strong excited-state emission of vaporized species such as Al, Ti, and Cu (in both the atomic and ionic states). In contrast, HMX produces only weak emissions from elements such as C, H, N, and O, which also persist for significantly shorter durations.

Rheological Behaviour of 3D Printing Inks
The process for preparing the 3D printing ink via acoustic resonance is shown in Fig. 6a. The formulation of powders into printable inks constitutes a critical step in direct ink writing (DIW) 3D printing technology, where the rheological properties serve as decisive parameters for successful printing. These rheological characteristics were systematically examined through rotational and oscillatory rheological measurements. Specifically, rotational tests were conducted to evaluate the flow properties of the inks, whereas oscillatory tests were conducted to characterize their viscoelastic deformation behaviour. To elucidate the effect of the ATC–HMX composite architecture on the energy release efficiency, we selected the 40ATC–60HMX composition as our primary research focus because of its superior combustion performance and energy release characteristics. The rheological performance test results are presented in Fig. 6c-d. The particle size distribution of the solid particles in the printing ink is shown in Supplementary Fig. 10.

As shown in Fig. 6c, with increasing shear rate, the viscosities of both the HMX-based ink and the 40ATC–60HMX-based ink gradually decreased, which indicated shear-thinning behaviour. This ensures that during 3D printing, as the stress at the needle tip increases, the viscosity of the ink rapidly decreases, thereby enabling smooth flow. Moreover, the viscosity of 40ATC–60HMX ink decreased quasilinearly with increasing shear rate, which is more favourable for printing. As shown in Fig. 6d and e, for the HMX ink, the storage modulus (G') remained lower than the loss modulus (G") throughout the shear strain process, which indicated that the viscous behaviour was dominant and that a certain flowability maintained. In contrast, for 40ATC–60HMX ink, below 0.102% shear strain, G' > G", which indicated dominant elastic behaviour (gel state). Above 0.102% shear strain, G' < G", which indicated dominant viscous behaviour (fluid state). During shear strain, irreversible structural changes occurred in the samples, thus placing them in the nonlinear viscoelastic region. As the shear strain increased, the flowability continuously improved, which makes them suitable for direct ink writing. This study revealed that under strain, energetic inks can simultaneously exhibit both elastic and viscous properties. This enables high-viscosity inks to have sufficient flowability for extrusion through small nozzles while recovering their original high-viscosity state afterwards.

Microstructural, Density and Sensitivity Analyses of the 3D-Printed Samples
The acoustically homogenized ink was transferred to a direct ink writing (DIW) 3D printing system for additive manufacturing, with the printing principle illustrated in Supplementary Fig. 11. The printing process is shown in Fig. 7a, and the printed samples are shown in Fig. 7b-h. The microstructure and elemental distribution of the 3D-printed samples are shown in Fig. 7e-i. The SEM images demonstrate that the printed samples maintained overall structural integrity with clear interfacial contact between HMX and 40ATC–60HMX. EDS mapping revealed uniform distributions of C, N, O, Al, Ti, and Cu, which indicated homogeneous mixing of components during printing and controllable structural formation. As shown in Figs. 7e, owing to the large particle size of HMX, which created spatial steric hindrance between the particles, solvent evaporation led to the formation of visible pores/cavities on both the surface and cross-section of the HMX strands, with more pronounced porosity on the surface. In contrast, the 40ATC–60HMX strands exhibited smooth surfaces (Fig. 7f) without observable defects, and their cross-sections showed densely packed particles. High-magnification images (Fig. 7i) reveal that smaller Al/Ti/CuO particles remained effectively bonded to larger HMX particles via binders, thereby achieving particle gradation and dense packing without disrupting the original system architecture, which is a beneficial feature for performance improvement. As shown in Fig. 7g, the “triangular” HMX/40ATC–60HMX composite samples developed interfacial gaps at junctions because of differences in particle size and postcuring shrinkage rates between the two materials. The cylindrical “core–shell” structured HMX and 40ATC–60HMX samples in Fig. 7h had smooth surfaces with tight interlayer bonding and no obvious defects, along with uniform elemental distributions. However, although the outer 40ATC–60HMX layer remained dense, the inner HMX core still develops porosity because of its large particle size and solvent evaporation. Notably, the interface shows excellent contact and a distinct elemental distribution, which confirms that direct ink writing enables high-quality fabrication of complex cylindrical composite structures.

The measured density of pure HMX was 1.5092 g/cm3, whereas the density of the 40ATC–60HMX composite was 1.7937 g/cm3. The results of standard impact, friction and electrostatic discharge sensitivity of the printed composite systems are summarized in Supplementary Table 3. As shown in the table, both the printed HMX and 40ATC–60HMX exhibited 0% electrostatic discharge sensitivity. However, compared with HMX, the incorporation of highly reactive Al/Ti/CuO significantly increased the impact (54%) and friction (80%) sensitivity of the 40ATC–60HMX composite system. Thus, compared with traditional manual casting methods, the remote printing process that is enabled by 3D printing technology offers increased safety.

Combustion and Energy Release Characteristics of 3D-Printed Samples
The 3D-printed HMX strands and 40ATC–60HMX strands that are shown in Supplementary Fig. 12a and b were ignited (open system). The sequential snapshots of HMX and 40ATC–60HMX combustion are presented in Supplementary Fig. 12c and d, respectively. The calculated stage-wise burning rates and average burning rates of the 3D-printed HMX strands and 40ATC–60HMX strands during combustion are shown in Fig. 8a and b, respectively. The 3D-printed HMX strands and 40ATC–60HMX strands exhibited different flame morphologies and burning rates during combustion (Supplementary Fig. 12). The flame of the HMX strands always pointed upwards, whereas the propellant of the 40ATC–60HMX strand jetted outwards in all directions with greater flame intensity and higher luminosity. Additionally, we found that the burning rate of the HMX strands first increased but then decreased sharply, whereas that of the 40ATC–60HMX strands decreased gradually across stages. The average burning rate of the 40ATC–60HMX strands (18.2 mm/s) was higher than that of the HMX strands (14.3 mm/s). The upwards flame during HMX line combustion was caused mainly by air convection because of density differences between hot and cold gases. After ignition, the flame quickly spread throughout the entire HMX line (0.2 s–0.6 s in Supplementary Fig. 12c), thereby resulting in nonuniform cross-sectional burning but axial flame propagation along the line. This was primarily because the large voids and pores between particles inside the HMX line provided excellent channels for combustion product diffusion, which facilitated flame propagation and resulted in faster burning rates at this stage. However, during the later combustion stage (1.0 s–1.4 s in Supplementary Fig. 12 c), the flame intensity significantly weakened, and the burning rate markedly decreased because most of the HMX particles had already participated in rapid combustion during the early stage, which left only the HTPB binder and a small amount of HMX particles to burn at a slower rate. Unlike the HMX strands, the 40ATC–60HMX strands exhibited not only upwards flames due to air convection but also multidirectional flame propagation, which was caused by thermal gas and combustion product expansion from the combined burning of HMX and Al/Ti/CuO. The 40ATC–60HMX strands had sufficient particle contact and a dense structure (Fig. 7f), which resulted in smaller differences in burning rates between stages. As HMX and Al/Ti/CuO were consumed during combustion, the burning rate gradually decreased until extinction. Compared with those of the HMX strands, the increased structural density and improved reactive properties of the ATC–HMX strands led to more complete, intense, and stable combustion of the energetic system, with faster burning rates.

The pressure evolution processes of the samples are shown in Fig. 8c, with the corresponding peak pressures and pressurization rates presented in Fig. 8d. As shown in Fig. 8c, when the 3D-printed HMX strands and 40ATC–60HMX strands (200 mg) were ignited by nickel–chromium alloy wires in a constant-volume combustion chamber (330 mL), their pressures increased to 0.41 s and 0.27 s, respectively, and then increased rapidly to reach their first peak pressures (P ). The pressures fluctuated within a certain range for 3–5 s before gradually decreasing as the combustion ended. Specifically, for the HMX strands, after the first peak pressure (P =85.92 kPa) was reached, the pressure decreased slightly before reaching a second peak (P =85.06 kPa). For the 40ATC–60HMX strands, after the first peak pressure was reached (P =94.96 kPa), the pressure fluctuated within a range, followed by two consecutive secondary and tertiary pressure increase processes (pink shading in Fig. 8c), and the second (P =109.75 kPa) and third (P =112.34 kPa) peak pressures were reached. The first and second peak pressures of the HMX strands were 85.92 kPa and 85.06 kPa, respectively, with a pressurization rate of 80.87 kPa/s. The first, second and third peak pressures of the 40ATC–60HMX strands were 94.96 kPa, 109.75 kPa and 112.34 kPa, respectively, with a pressurization rate of 149.25 kPa/s. The peak pressures and pressurization rates of the 40ATC–60HMX strands were higher than those of the pure HMX strands, and consecutive secondary pressurization processes occurred. In the combustion reaction process of the printed ATC–HMX samples, HMX improved the pressure output of ATC combustion, which provides guidance for the pressure output regulation of energetic materials.

Detonation and Energy Release Characteristics of 3D-Printed Samples
The sequential snapshots of the air explosion process of the HMX+ATC–HMX “core–shell” structural samples that were captured by the high-speed camera are shown in Fig. 9a The explosion field temperature at a typical moment during the later stage of HMX+ATC–HMX “core–shell” structural detonation is shown in Fig. 9b. The processed 2D temperature contour plot is shown in Fig 9c, and the 3D isosurface plot of temperature and 3D temperature isosurface with 2D planar projections are shown in Supplementary Fig. 13a and b, respectively. The infrared thermogram, 2D temperature contour plots, and 3D temperature isosurface with 2D planar projections of the explosion field at a typical moment during the later stage of pure HMX detonation are shown in Supplementary Fig. 14a, b, and c, respectively.

As shown in Fig. 9a, the HMX+ATC–HMX sample reacted instantaneously upon initiation and produced a bright detonation fireball that rapidly expanded to approximately 1.5 m in diameter. The flame structure exhibited two main characteristics: Between 25 µs and 150 µs, the fireball expanded rapidly in the horizontal (radial) direction. This expansion is attributed to the reaction of the outer 40ATC–60HMX composite material, which was activated by the explosive drive. Simultaneously, a mushroom cloud-like flame surge developed vertically (axially) above the fireball. This phenomenon resulted from the constrained explosion of the inner HMX core by the outer ATC–HMX shell. The confinement effect enhanced the detonation, and a vertical mushroom cloud-shaped fireball was produced. Additionally, as the fireball continued to grow, after 175 µs, multiple expanding spherical flame balls became visible in the lower-central region of the fireball. This effect occurred because ATC–HMX fragments, which were fractured by the high-temperature detonation shock wave, underwent deflagration reactions within the explosive reaction zone under the detonation driving force. These reactions released their stored energy, thereby compressing the surrounding air and creating multiple spherical deflagration "bubbles," which appear as spherical flames in the images. These flames provided energy compensation for the attenuation of the detonation wave and sustained increased aftereffect energy release throughout the system. The detonation dynamics of the 3D-printed HMX+ATC–HMX core–shell architectures are shown in detail in Supplementary Movie 5.

As shown in Fig. 9b-c and Supplementary Fig. 13a and b, the HMX+ATC–HMX samples with a “core–shell” structure generated exceptionally high temperatures during the late stage of the explosion. The maximum temperature in the high-temperature field reached 1827.2 °C, which represented a 16.65% increase compared with the maximum temperature of pure HMX (1566.4 °C, as shown in Supplementary Fig. 14). The average temperature was 1374.7 °C, with a minimum temperature of 1046.8 °C. Moreover, the high-temperature zone (>1000°C) exhibited a broader yet more concentrated distribution (within the green frame in Fig. 9b) that covered the majority of the detonation area. These results clearly demonstrate that the ATC–HMX energetic material was promptly activated during explosive detonation, which rapidly triggered thermite reactions that released substantial heat while simultaneously ejecting material radially. This combined process significantly increased both the intensity and the spatial coverage of the high-temperature field, thereby ultimately resulting in increased afterburning temperature effects throughout the entire explosion field.

The key shockwave parameters of energetic materials following atmospheric detonation include peak overpressure (ΔP), positive-phase duration (t₊), and positive-phase impulse (I₊). Peak overpressure induces localized structural damage, whereas impulse, which is defined as the momentum that is transferred per unit area, characterizes the instantaneous energy delivery to structures and quantifies the mechanical work capacity of the shockwave. For explosive detonations, the positive-phase impulse is calculated by time-integrating the overpressure profile during the positive-phase duration, and the calculation formula is shown in Equation 3.

𝐼 = ∫
𝑡𝑎+𝑡+∆𝑝(𝑡)𝑑𝑡
(3)
+ 𝑡𝑎
In Equation 3, I₊ denotes the positive-phase impulse (Pa·s), ΔP(t) represents the time-dependent overpressure function (Pa), tₐ represents the shockwave arrival time (s), and t₊ indicates the positive-phase duration (s).

The overpressure–time histories that were recorded at 0.33 m and 0.66 m from the explosion centre during free-field detonation tests of ATC–HMX composite charges are shown in Fig. 9d, and the derived impulse–time curve for the HMX+ATC–HMX core–shell structure detonation is shown in Fig. 9e. The shock wave overpressure–time history curve that was generated by the detonation of pure HMX is shown in Supplementary Fig. 15. The data in Fig. 9d demonstrate that the HMX+ATC–HMX “core–shell” structural sample instantaneously generated a shock wave during free-field detonation, which produced a shock overpressure that rapidly reached the peak pressure before it underwent fast decay. The peak overpressures of the HMX+ATC–HMX core–shell structure at 0.33 m and 0.66 m from the detonation centre were measured at 2.26 MPa and 0.47 MPa, respectively. These values represent increases of 18.95% and 67.86% compared with those of pure HMX (1.90 MPa and 0.28 MPa, respectively, as shown in Supplementary Fig. 15), thus indicating significant increases in the shock wave overpressure generated by the ATC-containing composite structure, with a more pronounced increase observed in the far field. The positive-phase impulses at different locations increased progressively over time and reached 80.47 Pa·s and 27.20 Pa·s at 0.33 m and 0.66 m, respectively (Fig. 9e). Notably, the overpressure–time history curve exhibits significantly more pronounced signal noise at 0.33 m than at 0.66 m. This phenomenon is attributed to the ejection of energetic ATC–HMX material during detonation, where dispersed molten metallic fragments physically impacted the pressure sensors, which caused signal perturbations.

Fig. 9f and g show the images of the explosion field generated by the explosion of the 3D-printed HMX+ATC–HMX “core–shell” structural sample, captured simultaneously by two different surveillance cameras located inside the explosion chamber at a typical moment. As shown in Fig. 9f and g, the 3D-printed HMX+ATC–HMX “core–shell” structure sample strongly affected the target plate and target area around the explosion centre during the explosion. The sandbags on the ground were broken after being impacted by the shock wave, smoke appeared, and the cotton layer on the target plate fell to the ground. Moreover, the large fireball that was produced by the explosion was incandescent in the centre, the explosion diameter was greater than 1.5 m, and a large amount of smoke was produced. Interestingly, after the explosion of the HMX+ATC–HMX “core–shell” structure samples, many “concentrated” combustible fragment jets spread out from the explosion centre in a spherical shape and hit the target, thereby damaging it, and some fragments reacted with “microexplosions” while they spread and continued to disintegrate and rupture. This combustible fragment flow consisted of dispersing and reactively burning ATC–HMX fragments and particles. Specifically, the inner HMX core detonated first, which generated extreme temperatures and pressures that instantaneously initiated the explosion of the outer ATC–HMX shell. Driven by the detonation wave, the ATC–HMX was rapidly activated, underwent fragmentation, and ignited, which led to reactive combustion. These fragments were subsequently dispersed radially by the shock wave. Upon encountering air within the high-temperature explosion field, the flying fragments underwent additional fragmentation, which resulted in a secondary “microexplosion reaction”.

In summary, the 3D-printed cylindrical core–shell architecture, which comprises an HMX core and a reactive 40ATC–60HMX shell, enables controlled energy release through interfacial interactions between the two components.

Calculation of thermodynamic parameters for the ATC–HMSX composite system
The combustion performance and energy release characteristics of ATC–HMX composite systems are governed by multiple thermodynamic parameters, including the adiabatic flame temperature (AFT), heat of reaction (H), content of condensed-phase products (M ), peak pressure (P), and gas-phase volume (V ). In this study, ATC–HMX formulations with optimized AFT and peak pressure were specifically targeted. The adiabatic flame temperature refers to the maximum theoretical combustion temperature under ideal conditions, whereas the peak pressure refers to the highest pressure that is attained during the reaction process. The interaction between Al/Ti/CuO and HMX involves complex multistage reactions. Based on the principle of Gibbs free energy minimization, the thermodynamic parameters of ATC-HMX were calculated using the REAL program, as shown in Supplementary Fig. 16. The composition of the ATC-HMX system during the calculation process of the REAL program is shown in Supplementary Table 4. Supplementary Fig. 16b shows the relationship curves of P and AFT versus the composition of ATC-HMX. The calculation results indicate that the AFT of the ATC–HMX system reaction first increased but then decreased with increasing ATC content. When the ATC content in ATC–HMX was 40% and 50%, the AFT values of the system reaction were relatively high (3445.88 K and 3457.69 K, respectively), with minimal difference between them, which indicated that more complete reactions occurred in the system at these compositions. Moreover, the P of the ATC–HMX system reaction tended to decrease with increasing ATC content, with values of 0.51 MPa and 0.46 MPa for the 40ATC–60HMX and 50ATC–50HMX systems, respectively. Therefore, when both AFT and P indicators are comprehensively considered, the 40ATC–60HMX system demonstrated more complete overall reactions, better matching between energy and structural composition, and higher energy release efficiency.

Synergistic Mechanisms of Al/Ti/CuO–HMX Composites
Based on the aforementioned findings, to systematically elucidate the synergistic effects among components in the ATC–HMX system and the governing mechanisms of the effects of three-dimensional structural configurations on the reactive performance and energy release characteristics of composite materials, we comprehensively summarized the interactive synergistic mechanisms of the ATC–HMX composite system during reactions under various external stimuli, as shown in Fig. 10. Our findings demonstrate that the ATC–HMX composite system exhibits distinct synergistic and cooperative effects under various reaction conditions: Under slow heating rates (DSC analysis, Process A), HMX particles first undergo gradual melting and decomposition, generating heat and gaseous products that thermally activate adjacent ATC particles via heat conduction and gas diffusion; the activated ATC particles then undergo surface discoloration, core–shell melting/fracturing, and thermite reactions, whose feedback heat and metallic products further promote HMX decomposition. During laser-ignited combustion (Process B), ATC particles react preferentially, producing color changes, melting/fracturing, flame emission, and energetic fragments that ignite HMX, whose subsequent exothermic decomposition in turn intensifies ATC combustion through synergistic interactions. Under high-energy laser irradiation (Process C), ATC and HMX particles react almost simultaneously via instantaneous melting/vaporization and plasma formation, with their energetic gaseous products mutually promoting each other. In the combustion/deflagration of 3D-printed cylindrical samples (Process D), HMX rapidly melts and decomposes, generating heat and gases that propagate through HTPB binder interfaces to activate ATC particles; the triggered thermite reactions then yield fragmenting particles, flames, and heat, which reciprocally enhance HMX energy release. Through such particle-level synergistic interactions, the total energy output of the system is ultimately amplified by superposition effects.

Methods
Materials
Aluminium (Al, 1~3 μm) with a purity of 99.5% was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., China. Titanium (Ti, 100 nm~1 μm) with a purity of 99.5% was purchased from Shanghai Macklin Biochemical Co., Ltd., China. Copper oxide (CuO, 20~60 nm) with a purity of 99.5% was purchased from Shanghai Yien Chemical Technology Co., Ltd., China. N-hexane (GC) (purity > 99.5%) was purchased from Sinopharm Chemical Reagents Co., Ltd., China. Hydroyl-terminated polybutadiene (HTPB) and toluene diisocyanate (TDI) were purchased from Shanghai Macklin Biochemical Co., Ltd., China. Ethylacetate (AR) and ethanol (AR) were purchased from Beijing Tong Guang Fine Chemicals Co., Ltd., China. HMX (Type Ⅴ) was obtained from Gansu Yinguang Chemical Industry Group Co., Ltd. All the reagents were used as received without additional purification.

Preparation of ATC–HMX Composite Particles
The “lychee-like” core–shell-structured Al/Ti/CuO MICs (Al:Ti:CuO = 29.89:12.81:57.3 wt%) were first synthesized via a chemical reaction-inhibited ball milling method under mechanochemical forces by following our previously reported protocol46. The as-prepared Al/Ti/CuO MICs were subsequently blended with HMX at four distinct mass ratios (20:80, 30:70, 40:60, and 50:50 wt%) and subjected to acoustic resonance processing (amplitude intensity: 50 g; mixing duration: 20 min). This mixing technique combines macroscopic vibration blending with microscopic acoustic streaming effects through low-frequency, high-acceleration vertical oscillations and yielded four composite formulations: 20ATC–80HMX (20 wt% Al/Ti/CuO + 80 wt% HMX), 30ATC–70HMX, 40ATC–60HMX, and 50ATC–50HMX. A schematic illustration of the preparation process is shown in Fig. 1a. The acoustic resonance was operated at an acceleration of 50 g and a resonance frequency of 62 Hz.

Preparation of ATC–HMX Printing Ink
The ATC–HMX-printed ink was prepared using hydroxyl-terminated polybutadiene (HTPB) as the binder and ethyl acetate as the solvent; the solid content was 88%, with a mass ratio of 40ATC–60HMX powder to HTPB of 88:12. A control HMX sample (HMX:HTPB = 88:12) was also prepared for comparison. For a representative 50 g batch of 88% solid content 40ATC–60HMX/HTPB ink, (10.00±0.01) g of ethyl acetate was first measured into a beaker, followed by the addition of (6.00±0.01) g of HTPB and the curing agent TDI. The mixture was ultrasonically stirred for 10 min to achieve initial homogeneity before incorporating (44.00±0.01) g of 40ATC–60HMX mixed powder and ultrasonic mixing for another 10 min. The ink was then subjected to acoustic resonance mixing at an acceleration of 50 g for 50 min, during which the coupled macrovibration and microacoustic streaming effects transformed the initially disordered particulate system into small spherical aggregates that progressively coalesced into a completely homogeneous ink (Fig. 6a), as schematically illustrated in Fig. 6b, with the final uniform ink sealed for subsequent use in additive manufacturing applications.

3D Printing of ATC-HMX Samples
To regulate the reaction performance and energy release characteristics of the composites through the material macrostructure, the energetic ink was 3D printed using the direct ink writing extrusion system that is shown in Supplementary Fig. 11. Printing was conducted using an Ultimus V Nordson ASYMTEK printer that was equipped with a pneumatic extrusion system. The prepared energetic ink was loaded into a 30 cc syringe and extruded through a nozzle with an inner diameter of 1.3 mm onto a substrate platform. A rectangular printing path of 10 cm × 10 cm was used, with an extrusion pressure of 32 psi and a print speed of 6 mm/s. The printing process is shown in Fig. 7a, and the printed samples are shown in Fig. 7b-h. (In Fig. 7, white represents HMX, and black represents 40ATC–60HMX). The printed samples include “triangular” HMX and 40ATC–60HMX composites, 40ATC–60HMX strands, and cylindrical coaxial “core–shell” structure composites with HMX and 40ATC–60HMX (the cylindrical core–shell structure consists of an HMX core encapsulated by a 40ATC–60HMX shell). The printed samples were then cured in a vacuum oven at 60°C for 72 hours obtain the final formed specimens.

Characterization
Microstructural characterization was performed using scanning electron microscopy (SEM, S-4800, Hitachi, Japan) and transmission electron microscopy (TEM, Tecnai G2 F30, FEI, USA) with energy-dispersive X-ray spectroscopy (EDS, SuperX, FEI, USA). The phase composition was analysed by X-ray diffraction (XRD, D8 Advance, Bruker, Germany), and the chemical states were determined via X-ray photoelectron spectroscopy (XPS, ESCALAB25R0Xi, Thermo Fisher Scientific, USA).

The TG-DSC-FTIR-MS coupled technique was employed to comprehensively analyze the endothermic/exothermic behavior and mass loss/gain of the materials, while simultaneously characterizing the gaseous products, thereby providing a more thorough understanding of their thermal response. In this setup, the TG-DSC analyzer is connected to the mass spectrometer and FTIR spectrometer via capillary quartz tubes for real-time transfer of gaseous decomposition products. During operation, all instruments were started simultaneously by the thermal analysis software, allowing for the synchronous real-time acquisition of thermal, mass, and product evolution signals. To investigate the thermal reaction behavior and decomposition products of the sample, it was analyzed using this coupled TG-DSC-FTIR-MS system (TG-DSC-FTIR-MS Combined System, NETZSCH-STA 449 F3+QMS 403D+ThermoFisher-Nicolet iS50, NETZSCH, Germany, and Thermo Fisher Scientific, USA.) under the following conditions: argon atmosphere, a flow rate of 50 mL/min, a heating rate of 10 K/min, and a sample mass of 3±0.2 mg.

Constant volume combustion tests are usually used to measure the pressure output that is related to energy release68. The increase in pressure is an index of the intensity of combustion and gas expansion and is caused by gas generation and local air thermal expansion during the chemical reaction of energetic materials69. At atmospheric pressure, a powdered sample (200 ± 2 mg) was placed in a quartz crucible and inserted into a constant-volume combustion chamber (fixed volume: 330 mL, Supplementary Fig. 17a). The sample was ignited by a pre-embedded Nichrome wire (Φ 0.03–1.0 mm), which was heated via a DC power supply. The combustion generated a rapid pressure increase and produced a peak pressure (P ) at a specific pressurization rate (P ). The pressure transient was recorded using a ZQ-Y3 pressure sensor (Zhongnan Instrument Co., Ltd., Changsha, China) and a DPO7104 digital oscilloscope (Tektronix Inc., USA). The pressurization rate was determined from the slope of the pressure–time curve between 10% and 90% of P 70. The combustion pressure output test of 3D printed samples in the atmosphere is the same as the above experimental method.

The heat of combustion of the sample was measured using a TRHW-7000C oxygen bomb calorimeter (Hebi Tianrun Electronic Technology Co., Ltd., China) (Supplementary Fig. 17b) under atmospheric pressure; the calorimeter consisted primarily of an oxygen bomb, an insulating jacket, a stirrer, an ignition unit, a temperature measurement and control system, and distilled water. The fundamental principle of the measurement is as follows: The test sample is placed inside the oxygen bomb, which is then immersed in water. Typically, a 200 ± 2 mg sample was placed into a sealed reaction chamber and subsequently ignited using a nickel-chromium wire with a diameter of 0.2 mm under a 5 A current. The heat released from the complete combustion of the sample causes an increase in the water temperature. By recording the initial and final water temperatures, the heat that is required for this temperature change is calculated, which corresponds to the heat of combustion of the sample. For each experiment, a weighed sample was placed in the crucible. A Nichrome wire of a specified length was connected to the ignition electrodes, and the measurement was initiated via program control. Each sample was tested in triplicate, and the average value is reported.

Combustion experiments were conducted in a sealed chamber with multiple viewports under an inert atmosphere, as shown in Supplementary Fig. 18. The chamber consists primarily of observation windows, a shell, a gas inlet, and an exhaust port. The top gas inlet serves as the positive electrode, and the shell acts as the negative electrode. During the experiment, a sample of 200 ± 2 mg was placed in a crucible and positioned inside the visualized sealed combustion chamber (volume: 400 mL). After the chamber was evacuated, it was filled with nitrogen at 0.5 MPa. The sample was ignited by heating an embedded nickel–chromium alloy wire within the powder via a DC power supply that was connected to the positive and negative electrodes (current: 5 A, model: IT-M3144; ITECH Electronics Co., Ltd., Nanjing, China). The combustion process of the sample in the inert atmosphere was recorded using a high-speed camera (model: Revealer X113; Hefei Zhongke Junda Vision Co., Ltd., China).

Flame propagation, which is closely associated with the gas production rate and reaction kinetics, serves as a fundamental parameter for evaluating combustion performance in open systems. A laser ignition experiment was conducted on a powder sample (200±2 mg) using a CO laser (model: K808-25W; Beijing Kaipulin Photoelectric Technology Co., Ltd., China). The flame evolution and temperature change during combustion in an open system were simultaneously recorded by a high-speed camera and an infrared thermal imager, respectively. The spot diameter of the CO laser was 3.0 ± 0.5 mm, with a power of 100 W. Combustion events were captured at 5000 fps using a Revealer X113 high-speed camera, with simultaneous temperature monitoring via an SC300-series infrared imager (FLIR Systems, USA). Ignition delay was defined as the interval between laser initiation and the first visible spark. A schematic diagram of the laser ignition test experimental device is shown in Supplementary Fig. 19.

To investigate the combustion characteristics of HMX and ATC–HMX under oxygen-deficient and weakly confined conditions, we loaded 50 mg of HMX and ATC–HMX powders into quartz glass tubes (as shown in Supplementary Fig. 20) with an inner diameter of 3 mm, a wall thickness of 2 mm, and a length of 5 cm. The tubes were sealed at one end and open at the other end. After natural settling, the powders were ignited at the open end using a CO laser to study their combustion performance under geometric confinement.

To investigate the response behaviour and state of materials under transient high-temperature heating, high-energy laser-induced ignition experiments were conducted on small-scale samples (milligram level)71, 72, with the ignition and shock wave evolution processes recorded using a high-temporal-resolution camera. Schlieren imaging73, a conventional technique for visualizing refractive index gradients along the optical path, was employed to analyse the temporal characteristics of laser-generated plasma and shock waves. The induced dynamics were investigated using a custom laser schlieren system (Supplementary Fig. 21) that consisted of three integrated subsystems: (1) a reaction system that employed a Nd:YAG solid-state laser (Spitlight1000.2-10, InnoLas Laser Company, Germany, with a wavelength of 1064 nm, a maximum energy of 1030 mJ, and a spot diameter of 6 mm) as the energy source; (2) a schlieren imaging system that incorporated a JML-C2 flash background light source (Rapp OptoElectronic, Germany) and an SIMD8 ultrahigh-speed camera (Specialized Imaging, UK) with a minimum exposure time of 5 ns for shockwave visualization; and (3) a control system that comprised a pulse signal generator (Model DG535, Stanford Research Systems, USA) and data acquisition software. Sample preparation involved uniformly depositing 50±2 mg of test material as 0.5±0.1 mm thick layers on 12 mm diameter stainless steel moulds using double-sided adhesive, with complete coverage of the circular mould surface ensured.

The rheological behaviour of the printed slurries was characterized using a rotational rheometer (MCR 72, Anton Paar, Austria). Measurements were conducted at 25°C with a 1 mm gap. Shear rate sweeps were performed in logarithmic mode from 0.1 to 100 s-1 to evaluate the shear-dependent viscosity profile. Additionally, amplitude sweeps were carried out at a fixed frequency of 10 rad/s with a strain that varied logarithmically between 0.01% and 100% to investigate the strain-dependent viscoelastic properties, including the storage modulus (G') and loss modulus (G'').

The densities of the printed samples were measured using an MDJ-120TEM densimeter (Shanghai Yixin Scientific Instrument Co., Ltd., China). In accordance with GJB 772A (Explosives test methods, China), standard impact, friction, and electrostatic discharge sensitivity tests were conducted on the printed composite systems.

To investigate the detonation performance of 3D-printed HMX+ATC–HMX “core–shell” composite charge samples (the cylindrical “core–shell” structure of HMX+ATC–HMX consists of an HMX core that is encapsulated by a 40ATC–60HMX shell), air blast experiments were conducted in an explosion chamber according to the setup that is shown in Supplementary Fig. 22. The sample dimensions were Φ30 × 40 mm. The free-field overpressure from the sample explosion was measured using a model 137B22 shock wave pressure sensor (PCB Piezotronics, USA). The signal was then conditioned by a model 483C signal conditioner (PCB Piezotronics, USA) and subsequently acquired by an NI PXIe-5162 high-speed data acquisition module (National Instruments, USA), with the system sampling rate set at 1 GHz. A high-speed camera (SH6-116, Shenzhen SinceVision Technology Co., Ltd.; frame rate: 40,000 fps) and a high-temperature infrared imager (MAG-F7(E), Shanghai Magnity Technologies Co., Ltd.; frame rate: 131 fps) were used to record and monitor the detonation process of the sample. Simultaneously, two monitoring cameras inside the explosion chamber were used to observe the overall macroscopic reaction of the samples. Composite witness plates that were composed of 2A12 duralumin and cotton were used to assess the effects of the blast diameter and macroscopic damage at distances of 50 cm, 75 cm, 100 cm, 125 cm, and 150 cm from the sample. The sample platform was positioned 1.5 m above the ground. Two overpressure measurement lines were arranged approximately 90° relative to each other. Each line contained two pressure sensors as measurement points, which were located 33 cm and 66 cm from the sample centre. The sensors were positioned at the same height as the charge in the same horizontal plane. An electric detonator was used to initiate the samples.

The theoretical thermodynamic parameters of the samples were calculated using the REAL-WIN thermodynamic program (version 3.0, evolved from an earlier ASTRA program), which simulates real experimental conditions. Under constant-volume and adiabatic conditions (V = 1.65 m3·kg-1, H = 0 kJ·kg-1), the volume of a closed bomb (330 mL) was input. Assuming no energy exchange with the surroundings, all energy released from the reaction was converted into a temperature rise of the system. The heated gaseous products expanded, exerting pressure on the vessel, thereby allowing the calculation of the combustion temperature (T, K) and pressure (P, kPa) at reaction equilibrium. Under constant-volume and isothermal conditions (V = 1.65 m3·kg-1, T = 298.15 K), the heat of combustion (Q, kJ·kg-1) and the mass fraction of condensed products (Mcond) at equilibrium were computed. Under constant-pressure and adiabatic conditions (P = 0.1 MPa, H = 0 kJ·kg-1), the energy released caused the gaseous products to expand, and the specific volume of the gas phase (Vg, m3·kg-1) at equilibrium was determined. Based on these three sets of conditions, the relevant thermodynamic parameters for the ATC-HMX system were calculated.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This manuscript reports a pioneering approach to designing and manufacturing high-performance metastable intermolecular composite (MICs)/energetic materials (EMs) composites with programmable architectures. This manuscript presents a highly innovative and significant study on the fabrication and characterization of MICs-enhanced EMs. The authors successfully integrate acoustic resonance-assisted synthesis with direct ink writing (DIW) 3D printing to create Al/Ti/CuO-HMX (ATC-HMX) composites with precisely controlled filamentary and core-shell architectures. The integration of acoustic resonance synthesis and DIW 3D printing is innovative and powerful. Compared with pure HMX, the resulting ATC-HMX composites, particularly the 40wt% formulation, exhibit outstanding and well-documented enhancements in energy release, reactivity, pressure generation, and combustion/detonation characteristics across multiple testing regimes, underpinned by thorough characterization and testing across multiple reaction scales and conditions (thermal decomposition, confined combustion, open deflagration, laser-driven shock, and printed structure combustion/detonation). The mechanistic insights into the ATC-HMX synergy and architecture-dependent energy release are valuable.\n\nThe research is exceptionally well-executed, clearly presented, and addresses a critical need for advanced, tailorable energetic materials in propulsion and detonation systems. The findings represent a substantial advancement in the field of additive manufacturing for energetics. The work represents a significant contribution to the fields of energetic materials, additive manufacturing, and propulsion/detonation science, with clear transformative potential. I strongly recommend acceptance of this excellent manuscript. The suggested minor revisions are optional but could further polish an already strong paper.\n\nMajor Strengths and Contributions:\n1. Novel Fabrication Strategy: The combination of acoustic resonance-assisted integration for homogeneous ATC coating on HMX followed by DIW 3D printing for programmable architectures (filament, core-shell) is highly original and effective. This provides unprecedented control over material structure and interface design in MIC/EM composites.\n2. Significant Performance Enhancement: The data convincingly demonstrates substantial improvements in key energetic performance metrics for the optimized 40wt% ATC-60HMX composition:\n• Reduced HMX decomposition onset temperature (-6.51℃).\n• Dramatically increased peak pressure (+60.45%) and pressurization rate (+2220.94%) under confinement.\n• Significantly higher heat release (+23.92%).\n• Self-sustained high-temperature combustion (1778-2030℃) with demonstrated Deflagration-to-Detonation Transition (DDT) potential under geometric constraints.\n• Generation of strong shockwaves (>900 m/s) and tunable plasma intensity under laser impact.\n• Enhanced burn rate (18.2 mm/s) and novel \"secondary pressurization\" behavior in printed filaments.\n• Powerful detonation characteristics in core-shell structures (1.5m fireballs, high overpressures up to 2.26 MPa, significant impulses).\n3. Comprehensive Characterization: The manuscript provides an exceptionally thorough analysis, spanning microstructure (uniform ATC coating, dense integration), thermal behavior, confined and open reactivity, laser-driven response, and the performance of the final 3D-printed structures. This multi-scale approach provides deep insights.\n4. Mechanistic Insights: The work goes beyond empirical results by elucidating synergistic mechanisms:\n• The proposed ATC dominance in early energy release (plasma) vs. HMX dominance in wave propagation (shock speed).\n• The role of composition and architecture (core-shell) in enabling DDT and enhancing post-detonation effects (fragment-driven deflagration supplementing energy release).\n5. Clear Demonstration of Structure-Performance Tailoring: The successful implementation and testing of different architectures (filament vs. core-shell) explicitly show how the developed platform enables performance tailoring through structural design, bridging advanced AM with energetic functionality.\n6. High Impact Potential: The demonstrated performance enhancements and the controllable synthesis/printing platform unlock significant potential for next-generation propulsion and detonation systems. The work is highly relevant to the field.\n\nClarity and Presentation:\nThe manuscript is generally well-written, logically structured, and the data is clearly presented. The Abstract and Conclusions accurately and concisely summarize the key findings and significance of the work.\n\nSuggestions for Minor Revisions (Optional - for Authors' Consideration):\n1. 3D Printing Parameters: While the success of DIW is evident, briefly mentioning key printing parameters (e.g., nozzle size, layer height, print speed) or challenges overcome for these specific energetic inks would be beneficial for reproducibility and readers interested in the AM aspect.\n2. ToC Figure: The ToC figure can further enhance clarity and impact, making it easier for readers to understand this work. (e.g. simple annotation of the schematic in the figure).\n3. Minor Typos/Grammar: A careful final proofread is recommended to catch any minor grammatical errors or typos (e.g., consistency in hyphenation like \"laser-ignited\" vs. \"laser driven\").", "reviewer_2": "The authors intended to prepare highly reactive MICs by DIW method. However, the paper is too complicated to be well-focused. The logic is not clear without sufficient innovative points. The combination of Al and Ti in nanothermites is not new, also, the use of MIC in combination with nitramines is not a new attempt as well. Therefore, this paper cannot be published in NC in its current form.\n\nAt first glance, the paper accumulates too much information without sufficient in-depth investigation regarding the mutual interaction mechanisms at either slow solid state thermal analysis or fast burning to declaration under laser shock. The major driving force and chemical pathways are not clear in all reactions. As a scientific paper, the merit of this formulation design should be persuasive, but this paper seems like an experimental report without sufficient instructive insights to the readers.\n\nSecondly, the reported DIW technology herein is not the advanced one, which uses only HTPB-TDI curing system. It largely depends on the solid loading of the compositions. If the solid loading is too high, there might be flow problems and otherwise the curing time is too long to be well shaped to obtain the desired charge structure. The defects herein must be a lot, and the bulk density should be far below the theoretical maximum density. Therefore, the detonation velocity and pressure cannot be higher than normal cured formulations with the same ingredients. Therefore, BET and density parameters could be measured and compared with normal cured ones.\n\nIn case of flame propagation, the rate greater than 900 m/s cannot be called as “shockwaves”; The explosive with thermobaric effects must have lower overpressure than normal explosives with less metal contents. The formulations of HPTB/RDX-88/12 may reach overpressure of 300 kPa at 2 m location.\n\nThe research is suggested to be focused on the reactivity and energy release mechanisms of the new formulations without HTPB, since there are no extra findings on DIW technology. The reaction mechanisms might be clarified without HTPB binder, which is too complicated to be well described. There is no concept of “acoustic resonance-assisted integration and direct ink writing”, since these two steps are separated. If the acoustic mixing is online, that would be much better.\n\nThe particle size distributions are the major issues for the manufacturing processes. It must be well studied if the authors focused on DIW technology.\n\nThe burning process must be measured in presence of N2 or Ar, better with pressure. The compositions of the condensed products must be measured. CEA calculations can be done for optimized formulations if HTPB is included. The thermal decomposition behavior was dominantly determined by the content of HMX, which generates most of the gaseous products. Therefore, if possible, in presence of different metals, the decomposition kinetics and mechanisms might be changed. As physical mixtures, the XRD and IR spectra of the MICs products are not important to present.\n\nThe English is not promising. There are a log of grammar errors and terminology problems, such as “Lines” should be “strands”. The revised paper is suggested to be submitted to CNF and PCI as more specified journals.", "reviewer_3": "The authors have demonstrated significant performance enhancements for monomolecular explosives such as HMX can be achieved by using 3D printing to incorporate thermites into an energetic composite. These composites, which have been comprehensively characterized, enable optimization of the microstructural architecture to facilitate their energy release. The manuscript is quite thorough and well-written, I have only minor suggestions for improvement.\n\n1) Ref 5: incomplete citation (pages missing)\n2) Ref 10: incomplete citation (report number missing?)\n3) Ref 23: does not fit citation context re: monomolecular explosives (paper is on Al and metal oxide reactions)\n4) Ref 24 and 25 also do not seem to fit the cited context\n5) Ref 41: incomplete citation (volume and pages missing)\n6) Line 226: The “cyan dashed box” in Fig 6a is very difficult to see, suggest making it a shaded box like the orange one.\n7) Line 310: Reword “Under the atmosphere of atmospheric pressure” for clarity\n8) Line 333: “Figure 9c” should be “Figure 9b”\n9) Figures 10 and 11a should have scale bars\n10) The temperature scale in Fig 11b is not legible (text is too small)\n11) It’s odd that the temperature color scale in Fig 11c is opposite that in Fig 11b – usually red is used for the highest temperature\n12) Why is the x-axis timescale in Fig 11c in seconds when the combustion occurs in less than 1 s (Fig 11a,b,d)? Also, why don’t the max temps correlate to the max flame sizes (i.e., the trends are not the same)?\n13) Supplementary videos should be named in accordance with their reference in the text (i.e., Video S1).\n14) Why wasn’t the confined ignition of Al/Ti/CuO shown for comparison in Fig 12 (or added to the Supplementary details)? If it didn’t ignite, the authors can just say that.\n15) How reproducible were the observed trends in the open and confined combustion experiments?\n16) Ref 67: incomplete citation (pages missing)\n17) How much sample was used in the open and confined ignition tests?\n18) The confined ignition tests were not mentioned in Section 2.4 or Fig S2, only in the discussion of the results – suggest keeping all experimental details together in Section 2.4 (and configuration diagrams in the Supplementary).\n19) Section 3.1.4: I don’t understand the use of the term “ultrafast” to describe these experiments, which use a nanosecond-pulsed laser to investigate the subsequent reactions on a microsecond timescale. “Ultrafast” refers to picosecond or femtosecond timescales. Similarly, the images obtained are “high-speed,” not “ultrahigh-speed.”\n20) Why doesn’t Fig S4 have the shock wave positions labeled for comparison to the images in Fig 13a?\n21) The increase in laser-induced plasma intensity in the presence of Al/Ti/CuO is primarily due to the strong excited state emission from vaporized species such as Al, Ti, and Cu (both atomic and ionic). In contrast, HMX has only weakly emitting species such as C, H, N, and O – and such emission lasts for much shorter timeframes.\n22) Recommend adding a table of instantaneous shock velocities in each stage for each sample (rather than the inset in Fig 13c). Comparison to neat HMX and neat Al/Ti/CuO would also be interesting.\n23) Fig 19: the experimental setup should go in Section 2.4 or the Supplementary.\n24) Be consistent with the nomenclature for the detonation charge, HMX+ATCHMX vs HMX+ATC-HMX vs HMX/ATC-HMX.\n25) Line 701: The sentence beginning “The reason for this…” needs re-written for clarity.\n26) How does the overpressure and target damage compare to neat HMX? What is the advantage of the HMX+ATC-HMX?\n27) Process D in Fig 25 should go from left to right as with Processes A-B.", "reviewer_4": "The submitted manuscripts by Ren and colleagues describe an unprecedented integration of the synthesis of energetic Metastable Intermolecular Composites (MICs) by the RAM technique and further 3D-printing. Although there is enough literature precedents about energetic MICs, the novelty of this work is highlighted by the unique methodology of synthesis and the corresponding enhancement of properties of these MICs. The authors have investigated all the relevant properties related to energetic MICs, ranging from combustion studies, detonation studies, rheological properties, and many more. The ATC additive lowers the decomposition temperature of HMX and enhances its energy output significantly. The authors also elaborately investigated the mechanisms of the interaction between ATC and HMX using the REAL software. The manuscript can be accepted for publication in Nature Communications after a minor revision considering the following points:\n\n1. Although the body and volume of the work done are huge, the length of the manuscript seems a bit stretched. The authors can think of summarizing significant findings using tables, figures, graphs, etc.\n2. Direct Ink Writing (DIW) of energetic composites is well explored in references 42-49. The novelty of the present work, as compared to these prior arts, should be explained clearly. Specifically, the advantages offered by the present 3D-printing methodology should be emphasized.\n3. Is it possible to provide experimental evidence regarding the advantages offered by RAM mixing as compared to traditional ball-milling? A performance comparison with the ATC-HMX composite prepared by conventional methods can be helpful.\n4. Did the authors test the impact, friction, and electrostatic discharge sensitivity of the 3D-printed composites?\n5. The authors should provide detailed information regarding the 3D printing, including nozzle diameter, pressure, speed of writing, etc. (Please see Section 2.4 in reference 45).\n6. Can the authors explain why the filaments show ‘secondary pressurizations’ while core-shell prints give a fireball?\n7. Why did the authors only consider HMX for their MICs? MICs with CL-20 are also known, and CL-20 often gives better energy output, although it is more sensitive.\n8. The performance of the present ATC-HMX composite should be compared with other related MICs and presented in a tabular form. (For eg. Al/Ti/CuO-B MICs previously reported by the authors)\n9. In the conclusion section, the authors claim that 3D printed ATC-HMX composites have a superior density to HMX. However, no numerical values are mentioned to justify this claim."}, "author_response": "Response to Reviewer #1 Comments\n[...]\nResponse to Reviewer #2 Comments\n[...]\nResponse to Reviewer #3 Comments\n[...]\nResponse to Reviewer #4 Comments\n[...]"}, {"round": 2, "reviewer_comments": {"reviewer_1": "All the comments have been addressed, and it can be accepted.", "reviewer_2": "the authors made significant improvements based on the comments. It is now acceptable for publication.", "reviewer_3": "The authors have thoroughly addressed all reviewer comments and the revised manuscript is an excellent candidate for publication. Some minor issues were introduced during the revision process:\n1) Check Table 1 for typos in shock velocities (“1.200”, “1.220”)\n2) Line 557: Supplementary Fig 5 consists of XRD patterns—nothing to do with the laser-induced shock velocities. I assume the authors meant Fig S7 (which still has “ultrahigh-speed” and “ultrafast” language in the caption). Check citations and order of figures/tables in the Supplemental section (e.g., line 611 callout to Fig S6 is also incorrect).", "reviewer_4": "The authors have efficiently addressed all my previous queries. In my opinion, the manuscript is now suitable for publication in the Nature Communications."}, "author_response": "Response to Reviewer #3:\nGeneral Response: We are delighted by Reviewer 4's positive assessment that our revised manuscript is “an excellent candidate for publication.” We are equally grateful for their meticulous attention to detail, which identified precisely the types of minor errors that can be introduced during the revision process. We have corrected all points raised and performed a comprehensive check to ensure the integrity of citations throughout the manuscript and Supplementary Information.\nComments 1:\n1) Check Table 1 for typos in shock velocities (“1.200”, “1.220”)\nResponse 1:\nThank you for pointing out the typographical issues in Table 1. We have carefully reviewed the table and corrected the formatting of the shock velocity values. The entries previously listed as “1.200” and “1.220” have been corrected to “1200” and “1220” respectively (with consistent units) to match the standard numeric representation used throughout the manuscript. These corrections are reflected in the revised Table 1.\nComments 2:\n2) Line 557: Supplementary Fig 5 consists of XRD patterns—nothing to do with the laser-induced shock velocities. I assume the authors meant Fig S7 (which still has “ultrahigh-speed” and “ultrafast” language in the caption). Check citations and order of figures/tables in the Supplemental section (e.g., line 611 callout to Fig S6 is also incorrect).\nResponse 2:\nWe appreciate the reviewer's careful reading in identifying these citation errors. We sincerely apologize for the inconsistencies, which were inadvertently introduced during the reorganization of the supplementary figures in the previous revision. We have now performed a comprehensive correction as follows:\nWe have carefully reviewed all citations to Supplementary Figures and Tables in the main text and have verified their accuracy against the final order of the Supplementary Information. We have also reviewed all figure and table callouts in the Supplementary Information and corrected inconsistencies in the numbering and order. Additionally, we revised the figure captions to remove imprecise descriptors like “ultrahigh-speed” and “ultrafast,” replacing them with clear, neutral terminology consistent with the manuscript text (e.g., “high-speed” and “fast”)."}]

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