3D Micro-nanostructures Research Articles

Nanomaterials Function in Additive Manufacturing

Nanomaterials are substances that have at least one dimension that falls within the three-dimensional nanoscale range or fundamental structural components made of substances that fall inside this range. Micro-nano 3D printing technology can realize the processing of 3D micro-nano structures with nanometer precision and has broad application prospects in many fields. Metals and polymers can be easily connected through bonding reactions to obtain metal-metal or covalent bonds in 3D printing. These potent chemical bonds make 3D-printed structures stable, and 3D printing of metals and plastics is developing rapidly. The review focuses on the latest developments in unique composite nanomaterials for different field applications, comprising nanomaterials and 3D printing technology. A summary of the mechanisms, functional characteristics, benefits, drawbacks, and applications of various nanomaterials used in scientific 3D printing includes metal-based nanomaterials, metal-organic frameworks, upconversion nanoparticles, and lipid-based nanoparticles. Finally, this study presents an overview and highlights the issues that need to be resolved for nanomaterials to continue to be developed for the advantages of 3D printing.

A 3D surface nanomechanical property mapping method with a magnetic-drive orthogonal cantilever probe.

Traditional force-distance curve based atomic force microscopy (FD-AFM) is limited to two-dimensional (2D) surface characterization, making the in situ mapping of three-dimensional (3D) surface nanomechanical properties (SNMP) challenging. This paper presents a multimode 3D FD-AFM based on a magnetic-drive orthogonal cantilever probe (MD-OCP) that can achieve SNMP imaging of 3D micro-nano structures with surface contour fluctuations reaching or exceeding several microns. Bending, torsion and vector tracking modes are integrated into this method for a 2D horizontal surface, 2D sidewall, and 3D surface mapping, respectively. The MD-OCP consists of a horizontal cantilever, a vertical cantilever with a protruding tip, and a magnetized bead. It can be utilized in the detection of deep trench and dense microarray units. The force analysis during 3D SNMP measurement is performed through mathematical derivation, which shows a clear relationship between effective indentation force, friction, and total tip-sample interactions. Single-point SNMP evaluation, discrete 2D SNMP imaging, and continuous omnidirectional 3D SNMP mapping of a 3D microarray unit verify the accurate and comprehensive measurement abilities of the reported method in its bending, torsion, and vector tracking modes. The experimental results demonstrate that this method can achieve excellent 3D quantitative characterization of topography and SNMP, including critical dimensions, adhesion, Young's modulus, stiffness, and energy dissipation, along a 3D device surface. This novel 3D FD-AFM technique has many potential applications in the further exploration of 3D micro-nano devices.

Three-Dimensional Kelvin Probe Force Microscopy.

Traditional Kelvin probe force microscopy (KPFM) is mainly limited to the characterization of two-dimensional (2D) surfaces, and in situ surface potential (SP) imaging along 3D device surfaces remains a challenge. This paper presents a multimode 3D-KPFM based on an orthogonal cantilever probe (OCP) that can achieve SP mapping of 3D micronano structures. It integrates three working modes: a bending mode for 2D horizontal surface imaging, a torsion mode for vertical sidewall imaging, and a vector tracking-based 3D scanning mode. The customized OCP has a nanoscale tip protruding from the side and underside of the cantilever, rather than the front, and the extended tip makes the proposed approach universally applicable for 3D detection from the nanometer to micrometer scale. The spatial resolution of the proposed method is analyzed by simulation, which shows it can reduce the cantilever homogenization effect. Linearity and energy resolution measurements show that the proposed method has comparable performance to traditional methods. A comparative experiment using a gold-silicon interface verifies the accuracy of the reported method in its bending and torsion modes. Further, the imaging ability of the 3D scanning mode is confirmed in the 3D characterization of a step grating. This technique is applied to the in situ characterization of a microforce sensor with microcomb structures. The experiment results show that this method can excellently achieve the 3D quantitative characterization of topography and SP, including critical dimensions and SP along a 3D device surface. This novel 3D-KPFM technique has many potential applications in the further exploration of 3D micronano devices.

General Fabrication of 3D Hierarchically Structured Bamboo-like Nitrogen-Doped Carbon Nanotube Arrays on 1D Nitrogen-Doped Carbon Skeletons for Highly Efficient Electromagnetic Wave Energy Attenuation.

Hierarchically three-dimensional (3D) micro-nanostructures have promising applications in multifarious fields. Herein, we report a general strategy, that is, in situ catalysis process, for fabrication of nitrogen-doped carbon nanotube (NCNT) arrays on one-dimensional (1D) nitrogen-doped carbon (NC) skeletons. The NCNT arrays branch out from the 1D NC surfaces, resulting in the formation of hierarchically 3D micro-nanostructures. The strategy is involved in the pyrolysis of M-precursor (M = Fe, Co, and Ni) nanowires with the assistance of dicyandiamide. During the synthesis process, the metal components in the precursors serve as catalysts for growing NCNTs, while dicyandiamide provides carbon and nitrogen sources. With the ongoing reaction, the NCNTs were catalytically grown and branched out from 1D NC skeletons. Through the strategy, three kinds of hierarchically 3D structures with encapsulated Fe/Fe3C, Co, and Ni nanoparticles, respectively, were fabricated successfully. As functional materials for attenuating electromagnetic wave energy, these hierarchically 3D structures exhibit satisfactory performances even at a low matching thickness, exceeding most of the carbon-based materials. Typically, the minimal reflection losses of the 3D structures can reach -10.0 dB even as the matching thickness is in the range of 1.4-2.0 mm. Experimental results demonstrate that the excellent attenuation properties toward electromagnetic wave energy are relative to high conduction loss at a low frequency and high dielectric relaxations at a high frequency as well as better impedance matching with the input impedance of the free space. Our method presented here opens a general way for the development of hierarchically 3D carbon-based micro-nanostructures for their practical applications.

Facile fabrication of functional 3D micro-nano architectures with focused ion beam implantation and selective chemical etching

In this work, a facile nanofabrication approach for functional 3D micro-nano architectures is developed. Freestanding silicon 3D micro-nanostructures are fabricated by precisely controlling and selective chemical etching of ion implanted patterns written by a focused ion beam (FIB). The etch-stop mechanism of gallium implanted silicon is investigated, with threshold ion dose determined between implanted and non-implanted surface. Computational Monte Carlo simulations reveal the spatial-distribution of implanted-ions, dislocated-atoms, and effects of ion energy, which contribute to the etching resistance in silicon and fabrication of suspended nanostructures. The precise nature, tuning of ion beam in a FIB enable complex pattern writing and the application of the proposed approach is further utilized towards realization of suspended and delicate 3D micro-nanostructures such as nanomesh, pyramids, nanotrumpets etc. in addition to nanowires with a high aspect ratio (≈625) and small diameter (~31 nm). Microscopic characterizations reveal the near-amorphous nature of the fabricated nanostructures, arising from the ion implantation during pattern generation. The fabricated nanostructures exhibit potential for unique optical properties and pyramids, nanotrumpet structures are further engineered for antireflection, color filtering applications respectively. The developed approach provides fabrication of 3D micro-nano architectures, with an outlook towards realization of Si based photonics devices, resonators, sensors etc.

Multifunctional 3D Micro-Nanostructures Fabricated through Temporally Shaped Femtosecond Laser Processing for Preventing Thrombosis and Bacterial Infection.

Blood-contacting medical devices that directly inhibit thrombosis and bacterial infection without using dangerous anticoagulant and antibacterial drugs can save countless lives but have proved extremely challenging. Here, a useful methodology is proposed that employs temporally shaped femtosecond laser ablation combined with fluorination to fabricate multifunctional three-dimensional (3D) micro-nanostructures with excellent hemocompatibility, zero cytotoxicity, outstanding biocompatibility, bacterial infection prevention, and long-term effectiveness on NiTi alloys. These multifunctional 3D micro-nanostructures present 0.1% hemolysis ratio and almost no platelet adhesion and activation, repel blood to inhibit blood coagulation in vitro, maintain 100% cell viability, and have exceptional stability over 6 months. Moreover, the multifunctional 3D micro-nanostructures simultaneously suppress bacterial colonization to form biofilm and kill 100% colonized Pseudomonas aeruginosa (P.aeruginosa) and 95.6% colonized Staphylococcus aureus (S.aureus) after 24 h of incubation, and bacterial residues can be easily removed. The fabrication method in this work has the advantages of simple processing, high efficiency, high quality, and high repeatability, and the new multifunctional 3D micro-nanostructures can effectively prevent thrombosis and bacterial infection, which can be widely applied to various clinical needs such as biomedical devices and implants.

Fabrication of multi-step swelling structures on 6H–SiC by using highly-charged Ar beams

A series of experimental studies on ion-beam-induced swelling of silicon carbide (SiC), a promising ultra-hard materials, have shown that the swelling height varies with irradiation parameters, such as ion type, fluence, and beam energy. In order to confirm the feasibility of the swelling effect as a fabrication process for 3D micro-nanostructures, the effect of beam energy on swelling of the SiC substrate and a two-step irradiation method were investigated by using Ar beams in charge states of 1+, 4+, and 7+. The swelling height increases linearly with the fluence of the Ar beam up to n ≈ 5 × 1015/cm2. In addition, the swelling height obtained by using Ar7+ ions is enhanced by about fivefold as compared with that for Ar1+. Multi-step swelling structures were fabricated through a two-step irradiation. A different irradiation pattern was used in each step, and the additivity of swelling height was confirmed. To understand the swelling behavior, the effect of irradiation is characterized by SRIM-2013 and the Rutherford backscattering-channeling technique.

Dual-3D Femtosecond Laser Nanofabrication Enables Dynamic Actuation.

Strategies that can make general materials smart are highly desired for developing artificial shape-morphing systems and devices. However, at present, it still lacks universal technologies that enable designable prototyping of deformable 3D micro-nanostructures. Inspired by natural automation systems, for instance, tendrils, leaves, and flowers deform dynamically under external stimuli by varying internal turgor, we report a dual-3D femtosecond laser processing strategy for fabricating smart and deformable 3D microactuators based on general photopolymers. By programming the size and distributions of voxels at the nanoscale, both the 3D profile and the 3D internetwork of a general photopolymer could be tailored in a controlled manner; thus, 3D microstructures encoded with precisely tailored networks could perform predictable deformations under certain stimuli. Using this dual-3D fabrication approach, energetic 3D microactuators, including a smart microflower, a responsive microvale, and an eight-finger microclaw, that permit controllable manipulation have been successfully developed.

Influence of LiAl-layered double hydroxides with 3D micro-nano structures on the properties of calcium sulphoaluminate cement clinker

The effect of LiAl-layered double hydroxides (LiAl-LDHs) with 3D micro-nano structures on the early properties and hydration process of calcium sulphoaluminate cement (CSAC) clinker was investigated. Three LiAl layered double hydroxides (LiAl-LDHs) with different particle size were prepared through a facile solvothermal method. CSAC clinker incorporating LiAl-LDHs with constant water to cement radio were made and tested. The results indicate that a higher content of LiAl-LDHs resulted in a faster hydration rate, a shorter setting time and a higher early compressive strength. Besides, with the decrease of the particle size of LiAl-LDHs, the hydration rate was accelerated with corresponding increase in compressive strength. However, the influence of particle size of LiAl-LDHs on the setting time of CSAC clinker is not significant. Moreover, the addition of LiAl-LDHs did not result in a new phase formed, but increased the quantity of hydration products providing higher compressive strength and shorter setting time.

Self-assembly of poly(p-phenylene)-based flower-like 3D micro-nanostructures

Poly(2,5-dioctyloxy-p-phenylene) was fabricated into Chrysanthemum-like, rose-like, and coil-like micro-nanostructures and porous sponge-like three-dimensional (3D) network via solution-phase self-assembly by two types of phase separations (continuous and dispersed phases) occurred by the dissolution of polar MeOH vapor and nonpolar hexane vapor into the polymer solutions, respectively. Morphological changes of polymers produced significant changes in the optical properties. It was concluded that the choice of a good solvent and nonsolvent vapor for hairy-rod polymers is a facile way to design and fabricate various super-macromolecular architectures.