The deposition of device-grade inorganic materials is one key challenge toward the implementation of additive manufacturing (AM) in microfabrication, and to that end, a broad range of physico-chemical principles has been explored for 3D fabrication with micro- and nanoscale resolution. Yet, for metals, a process that achieves material quality rivalling that of established thin-film deposition methods, and at the same time, has the potential to combine high throughput production with a broad palette of processable materials, is still lacking. Here, the kinetic, solid-state bonding of metal thin films for the additive assembly of high-purity, high-density metals with micrometer-scale precision is introduced. Indirect laser ablation accelerates micrometer-thick gold films to hundreds of meters per second without their heating or ablation. Their subsequent impact on the substrate above a critical velocity forms a permanent, metallic bond in the solid state. Stacked layers are of high density (>99%). By defining thin-film layers with established lithographic methods prior to launch, a variable feature size (2-50 mu m), arbitrary shape of bonded layers, and parallel transfer of up to 36 independent film units in a single shot, is demonstrated. Thus, the solid-state kinetic bonding principle as a viable and potentially versatile route for micro-scale AM of metals is established.

Additive microfabrication processes based on localized electroplating enable the one-step deposition of micro-scale metal structures with outstanding performance, e.g., high electrical conductivity and mechanical strength. They are therefore evaluated as an exciting and enabling addition to the existing repertoire of microfabrication technologies. Yet, electrochemical processes are generally restricted to conductive or semiconductive substrates, precluding their application in the manufacturing of functional electric devices where direct deposition onto insulators is often required. Here, the direct, localized electrodeposition of copper on a variety of insulating substrates, namely Al2O3, glass and flexible polyethylene, is demonstrated, enabled by electron-beam-induced reduction in a highly confined liquid electrolyte reservoir. The nanometer-size of the electrolyte reservoir, fed by electrohydrodynamic ejection, enables a minimal feature size on the order of 200 nm. The fact that the transient reservoir is established and stabilized by electrohydrodynamic ejection rather than specialized liquid cells can offer greater flexibility toward deposition on arbitrary substrate geometries and materials. Installed in a low-vacuum scanning electron microscope, the setup further allows for operando, nanoscale observation and analysis of the manufacturing process.

High-resolution additive manufacturing is a rapidly expanding field in microscale engineering. An approach of direct laser writing of inorganic materials now promises the facile 3D deposition of complex geometries in metals and their alloys.

Microscale particle-target interactions and the resulting modifications of the target material play a crucial role in the domains of industrial manufacturing and application process. As know that the processing and manufacturing, failure prevention, and even the spacecraft protection against hypervelocity micrometeorites and orbital microdebris. Based on such an interesting, noteworthy, and profoundly applied research, it quickly followed up and compiled a series of relevant studies for particle-target interactions of high-speed microparticle impact. Here, it discussed the gas-based, laser-based, and electrostatic-based of the high-speed microparticle impacts. Among these, laser-induced particle impacts stand out for their high throughput and the suitability for operation in small facilities or even on standard laboratory optical benches. Various behaviors have been observed with smaller projectiles, relatively high velocities, and extreme strain rates, which involved the description of launching system, dynamic capturing of high-speed videography, triggering and characterization of material response, and resulting material modification. Subsequently, it conducted a summary and future prospect of the focused topics. As expected that the particle-target interactions will become an effective tool for the study of microprocessing, multi-field coupling, material strengthening and modification, it will bridge multidisciplinary to understand the scientific phenomena involved in the impact process, also provides a novel strategy for the development of next-generation of ballistic impact testing.

Cold spray coatings are the sum of countless individual bonding events between single particles impacting on top of one another at high velocities. Thus, the collective behavior of microparticles must be considered to elucidate the origins of coating flaws at the scale of the particles and larger, or the dynamic evolution of the overall coating microstructure. Laser-induced particle impact testing (LIPIT) has been extensively used to study single-particle impacts, and in this work is adapted to study the accumulation of numerous particles with knowledge of each individual particle's impact parameters (particle size, velocity). The method reproducibly deposits stacks of gold particles (>20 particles) with different characteristic spectra of impact velocity. The observation of impactinduced erosion lets us define a critical velocity for material-build-up that is higher than that for singleparticle bonding. The quantitative single-particle data are analyzed in a correlative manner to the structure and flaws in the resulting stacks, providing some first statistical connections between, e.g., strain and recrystallization, or aberrant particle characteristics and defects. The results highlight opportunities for the study of many-particle phenomena in microparticle impact-from interaction of particles in cold spray to multi-step erosion processes-with a quantitative view of the behavior of single particles.

Across disciplines and length scales, alloying of metals is a common and necessary strategy to optimise materials performance. While the manufacturing of alloys in bulk and thin film form is well understood, the fabrication of alloyed 3D nanostructures with precise control over the composition remains a challenge. Herein, we demonstrate that electrohydrodynamic redox 3D printing from mixed metal salt solutions is a versatile approach for the 3D nanofabrication of alloys. We propose that the droplet-by-droplet nature of the electrohydrodynamic redox printing process allows straightforward electroplating of alloys with composition solely controlled by the composition of the electrolyte solution, independent of the reduction potential of the involved cations. As a demonstration of the direct control of composition, we deposit binary and ternary alloys of Ag, Cu and Zn. TEM microstructure analysis indicates homogeneous alloying at the nanoscale and the formation of a metastable solid-solution phase for Ag-Cu and a two phase system for Ag-Cu-Zn alloys. The straightforward approach to alloying with an electrochemical technique promises novel opportunities for optimisation of properties of 3D nanofabricated metals.

In the first decade of high-velocity microparticle impact research, hardly any modification of the original experimental setup has been necessary. However, future avenues for the field require advancements of the experimental method to expand both the impact variables that can be quantitatively assessed and the materials and phenomena that can be studied. This work explores new design concepts for the launch pad (the assembly that launches microparticles upon laser ablation) that can address the root causes of many experimental challenges that may limit the technique in the future. Among the design changes contemplated, the substitution of a stiff glass launch layer for the standard elastomeric polymer layer offers a number of improvements. First, it facilitates a reduction of the gap between launch pad and target from hundreds to tens of micrometers and thus unlocks a reproducibility in targeting a specific impact location better than the diameter of the test particle itself (±1.75 µm for SiO2 particles 7.38 µm in diameter). Second, the inert glass surface enables experiments at higher temperatures than previously possible. Finally—as demonstrated by the launch of thin-film Au disks—a launch pad made of materials standard in microfabrication paves the way to facile microfabrication of advanced impactors.

Electrohydrodynamic redox 3D printing (EHD-RP) is an additive manufacturing (AM) technique with submicron resolution and multi-metal capabilities, offering the possibility to switch chemistry during deposition “on-the-fly”. Despite the potential for synthesizing a large range of metals by electrochemical small-scale AM techniques, to date, only Cu and Ag have been reproducibly deposited by EHD-RP. Here, we extend the materials palette available to EHD-RP by using aqueous solvents instead of organic solvents, as used previously. We demonstrate deposition of Cu and Zn from sacrificial anodes immersed in acidic aqueous solvents. Mass spectrometry indicates that the choice of the solvent is important to the deposition of pure Zn. Additionally, we show that the deposited Zn structures, 250 nm in width, can be partially converted into semiconducting ZnO structures by oxidation at 325 °C in air.