Search results

The purpose of this paper is to present a novel and effective fabricating method of 3D ceramic photonic crystals with diamond structure.

The reverse diamond‐structure resin molds are fabricated by stereolithography (SL), then ceramic slurry is prepared and injected into the molds under vacuum condition. Subsequently, ceramic photonic crystals are obtained after vacuum freeze‐drying and sintering.

The combination of SL, gel‐casting and freeze‐drying could be used to fabricate the 3D ceramic photonic crystals with diamond structure which have intact structure and minimal shrinkage. The samples have been tested and the experimental results indicate that their band gap is in the range of 10.14‐12.20 GHz, consistent with the simulation results.

The influence of fabrication process on the photonic band gap needs further study.

This paper presents a novel fabricating method of 3D diamond‐structure ceramic photonic crystals based on SL, gel‐casting and freeze‐drying. The method fabricates complex ceramic photonic crystals with high accuracy and helps further research in this field.

Artificial electromagnetic (EM) medium and devices are designed with integrated micro- and macro-structures depending on the EM transmittance performance, which is difficult to fabricate by the conventional processes. Three-dimensional (3D) printing provides a new solution for the delicate artificial EM medium. This paper aims to first review the applications of 3D printing in the fabrication of EM medium briefly, mainly focusing on photonic crystals, metamaterials and gradient index (GRIN) devices. Then, a new design and fabrication strategy is proposed for the EM medium based on the 3D printing process, which was verified by the implementation of a 3D 90o Eaton lens based on GRIN metamaterials.

A new design and manufacturing strategy driven by the physical (EM transmittance) performance is proposed to illustrate the realization procedures of EM medium based device with controllable micro- and macro-structures. Stereolithography-based 3D printing process is used to obtain the designed EM device, an GRIN Eaton lens. The EM transmittance of the Eaton lens was validated experimentally and by simulation.

A 3D 90o Eaton lens was realized based on GRIN metamaterials structure according to the proposed design and manufacturing strategy, which had the broadband (12-18 GHz) and low loss characteristic. The feasibility of 3D printing for the artificial EM medium and GRIN devices has been verified for the further real applications in the industries.

The applications of 3D printing in artificial EM medium and devices were systematically reviewed. A new design strategy driven by physical performance for the EM device was proposed and validated by the firstly 3D printed 3D Eaton lens.

The purpose of this paper is to bring up the concept of multi‐material electromagnetic band‐gap structure (EBGs) and develop a method for its fabrication. Meanwhile, its microwave properties were studied and compared with the traditional EBGs consisting of two kinds of material.

Stereolithography (SL) and gel casting were used to fabricate 3D multi‐material EBGs. Resin mold was designed and fabricated based on SL process, slurries loaded with 55vol per cent Al₂O₃ and 55vol per cent TiO₂, respectively, were prepared, and using gel casting, multilayer EBGs with diamond structure were fabricated. T/R method was used to obtain the characteristic parameter S₂₁ of the EBGs; meanwhile, characters of their band structure were studied based on plane wave expansion method.

The fabricated EBGs with a TiO₂‐resin‐air structure showed a band gap from 11.7 GHz to 16.0 GHz along <1, 1, 0> direction; the EBGs with a TiO₂‐resin‐Al₂O₃ structure showed a band gap from 11.4 GHz to 11.9 GHz along <1, 1, 0> direction. Both of them agreed well with the simulation result. Also, through the study of multi‐material EBGs' microwave properties, it could be seen that this structure was a good approach to adjust the band gap.

With the concept of multi‐material EBG structure brought up, multilayer 3D EBGs were designed and fabricated based on SL combined with gel casting. It could be seen that multi‐material EBGs was a good approach to adjust the band gap. Also, the fact that the testing result matched the simulation validates the feasibility of the process.

The aim of this paper is to provide an easy method of extrusion freeforming to fabricate microwave electromagnetic bandgap (EBG) crystals. EBG crystals are periodic dielectric structures that can block wave propagation and generate a bandgap. These crystals can be used in high capability antennae, electromagnetic wave semiconductors, microresonators, high‐reflectivity mirrors and polarizing beam splitters.

The effects of extrusion process parameters and paste characteristics were investigated. Finally, one‐period and two‐period woodpile EBG crystals with bandgaps in the frequency region of 90‐110 GHz were fabricated and the bandgap was measured.

The filament diameter is influenced by whether extrusion is carried out with or without a substrate and by the free fall‐distance from the nozzle. The quality of lattice structures is dependent on paste flow and properties. A ceramic paste with 60 vol. % (the fraction of ceramic powder based on solvent‐free polymer) was well suited to fabrication. The solvent content also influenced the fabrication. The experimental results show that under ∼12 per cent solvent mass fraction in the paste and relatively high extrusion ram velocity (more than 0.014 mm/s) at a pressure of 14 MPa, samples with high quality were fabricated.

This paper demonstrates that the rapid prototyping method of extrusion freeforming can be applied for the fabrication of EBG crystals from ceramic powders and the important factors which influence the product quality are identified.

The purpose of this paper is to describe recent research involving the application of biomimetic design concepts to nanosensor developments.

Following a short introduction to nanobiomimetic concepts, this paper discusses a range of recent nanosensor developments whose designs mimic or use naturally‐occurring nanostructures or nanomaterials.

This shows that biomimetic design concepts are being applied to a range of nanosensors which have been shown to respond to a range of physical and chemical variables, often with very high sensitivities. Potential applications include homeland security and military uses, healthcare and robotics.

This paper provides details of recent nanobiomimetic sensor research which has potential in a range of critical applications.

The purpose of this study is to modify the FDM 3D printer to print with polystyrene (PS) microspheres as the printing material, thus enabling bottom-up structural color printing and evaluating structural color printing.

This study chose a range of different heated bed temperatures to determine a suitable temperature for accelerating the self-assembly of photonic crystals and printing structural colors on various substrates. In addition, this study enhanced the structural color by doping PS microspheres with different contents of Acid Black 210 dye and evaluated the color-enhanced structural color by eye and spectrophotometer under different light sources.

The results show that the modified 3D printer can be used for structural color printing, and 50°C is determined as the heated bed temperature. There are significant differences in structural colors when printing under different color backgrounds and material substrates, and corresponding suitable substrates should be selected according to the application. The doping of PS microspheres with varying contents of dye results in different color levels of structural color. As with pigment colors, the visual perception of structural color varies when viewed under different light sources.

This paper proposes to print structural colors low-costly, analyze structural colors under substrate and light source conditions, and expand the structural color gamut by enhancing structural colors, which has positive implications for further research on structural colors as printing colors.

We present 3D simulation of low loss splitters made on Lithium Niobate used in Mach-Zehnder interferometers. The interferometer consists of the splitters designed with photonic crystal structures at splitting point and bend positions for reduced size and loss, and straight sections as channel waveguides with high electro-optical coefficient r₃₃ of Lithium Niobate for reduced interactive length and modulating voltage π. The simulation shows a reduced coupling loss to 1.37 dB with the channel waveguides made suspended and V_π?is only 0.42V for interactive length of 200 um.

The purpose of this paper is to extend the generalized finite‐difference calculus of flexible local approximation methods (FLAME) to problems where local analytical solutions are unavailable.

FLAME uses accurate local approximations of the solution to generate difference schemes with small consistency errors. When local analytical approximations are too complicated, semi‐analytical or numerical ones can be used instead. In the paper, this strategy is applied to electrostatic multi‐particle simulations and to electromagnetic wave propagation and scattering. The FLAME basis is constructed by solving small local finite‐element problems or, alternatively, by a local multipole‐multicenter expansion. As yet another alternative, adaptive FLAME is applied to problems of wave propagation in electromagnetic (photonic) crystals.

Numerical examples demonstrate the high rate of convergence of new five‐ and nine‐point schemes in 2D and seven‐ and 19‐point schemes in 3D. The accuracy of FLAME is much higher than that of the standard FD scheme. This paves the way for solving problems with a large number of particles on relatively coarse grids. FLAME with numerical bases has particular advantages for the multi‐particle model of a random or quasi‐random medium.

Irregular stencils produced by local refinement may adversely affect the accuracy. This drawback could be rectified by least squares FLAME, where the number of stencil nodes can be much greater than the number of basis functions, making the method more robust and less sensitive to the irregularities of the stencils.

Previous applications of FLAME were limited to purely analytical basis functions. The present paper shows that numerical bases can be successfully used in FLAME when analytical ones are not available.

Virtual voxels (3D pixels) have traditionally been used as a graphical data structure for representing 3D geometry. The purpose of this paper is to study the use of pre‐existing physical voxels as a material building‐block for layered manufacturing and present the theoretical underpinnings for a fundamentally new massively parallel additive fabrication process in which 3D matter is digital. The paper also seeks to explore the unique possibilities enabled by this paradigm.

Digital RP is a process whereby a physical 3D object is made of many digital units (voxels) arranged selectively in a 3D lattice, as opposed to analog (continuous) material commonly used in conventional rapid prototyping. The paper draws from fundamentals of 3D space‐filling shapes, large‐scale numerical simulation, and a survey of modern technology to reach conclusions on the feasibility of a fabricator for digital matter.

Design criteria and appropriate 3D voxel geometries are presented that self‐align and are suitable for rapid parallel assembly and economical manufacturing. Theory and numerical simulation predict dimensional accuracy to scale favorably as the number of voxels increases. Current technology will enable rapid parallel assembly of billions of microscale voxels.

Many novel voxel functions could be realized in the electromechanical and microfluidic domains, enabling inexpensive prototyping of complex 3D integrated systems. The paper demonstrates the feasibility of a 3D digital fabricator, but an instantiation is out of scope and left to future work.

Digital manufacturing offers the possibility of desktop fabrication of perfectly repeatable, precise, multi‐material objects with microscale accuracy.

The paper constitutes a comprehensive review of physical voxel‐based manufacturing and presents the groundwork for an emerging new field of additive manufacturing.