Fabrication Of Three-dimensional Structures Research Articles

Multilevel design and construction in nanomembrane rolling for three-dimensional angle-sensitive photodetection

Releasing pre-strained two-dimensional nanomembranes to assemble on-chip three-dimensional devices is crucial for upcoming advanced electronic and optoelectronic applications. However, the release process is affected by many unclear factors, hindering the transition from laboratory to industrial applications. Here, we propose a quasistatic multilevel finite element modeling to assemble three-dimensional structures from two-dimensional nanomembranes and offer verification results by various bilayer nanomembranes. Take Si/Cr nanomembrane as an example, we confirm that the three-dimensional structural formation is governed by both the minimum energy state and the geometric constraints imposed by the edges of the sacrificial layer. Large-scale, high-yield fabrication of three-dimensional structures is achieved, and two distinct three-dimensional structures are assembled from the same precursor. Six types of three-dimensional Si/Cr photodetectors are then prepared to resolve the incident angle of light with a deep neural network model, opening up possibilities for the design and manufacturing methods of More-than-Moore-era devices.

Unlocking the out-of-plane dimension for photonic bound states in the continuum to achieve maximum optical chirality

The realization of lossless metasurfaces with true chirality crucially requires the fabrication of three-dimensional structures, constraining experimental feasibility and hampering practical implementations. Even though the three-dimensional assembly of metallic nanostructures has been demonstrated previously, the resulting plasmonic resonances suffer from high intrinsic and radiative losses. The concept of photonic bound states in the continuum (BICs) is instrumental for tailoring radiative losses in diverse geometries, especially when implemented using lossless dielectrics, but applications have so far been limited to planar structures. Here, we introduce a novel nanofabrication approach to unlock the height of individual resonators within all-dielectric metasurfaces as an accessible parameter for the efficient control of resonance features and nanophotonic functionalities. In particular, we realize out-of-plane symmetry breaking in quasi-BIC metasurfaces and leverage this design degree of freedom to demonstrate an optical all-dielectric quasi-BIC metasurface with maximum intrinsic chirality that responds selectively to light of a particular circular polarization depending on the structural handedness. Our experimental results not only open a new paradigm for all-dielectric BICs and chiral nanophotonics, but also promise advances in the realization of efficient generation of optical angular momentum, holographic metasurfaces, and parity-time symmetry-broken optical systems.

Understanding the yielding behavior of graphene oxide colloids via experimental strain decomposition

Graphene oxide (GO) has attracted attention in materials science and engineering due to its large aspect ratio and dispersibility in polar solvent including water. It has recently been applied to direct-ink-writing (DIW) printing to realize the fabrication of three-dimensional structures, suggesting a wide variety of potential applications. Without post-processing, DIW printing requires yield stress fluids to fully build three-dimensional objects. The key properties of these inks are the yield stress and the viscoelastic properties during yielding. DIW ink rheology has therefore received significant interest in materials science, as well as mechanical and chemical engineering. Despite this interest, the yielding process has not been clearly elucidated and understanding yielding remains an outstanding problem. In this study, we discuss the yielding behavior of GO colloids via oscillatory rheology by decomposing the total strain into the recoverable and unrecoverable parts through iterative experimental techniques. The recoverable and unrecoverable responses represent viscoelastic solid and plastic properties, respectively, and they are used to determine the averaged storage and dissipation of energies. By mapping these contributions, we more clearly elucidate the yielding behavior of the GO colloids and suggest guidelines for energy efficiency. Beyond the specific lessons learned regarding the DIW-relevant rheology of GO colloids, our study contributes to an evolving development of material-centric and energy-focused methods for understanding the out-of-equilibrium rheological physics associated with the yielding of soft materials.

Super-hydrophobic/hydrophilic patterning on three-dimensional objects

As superhydrophobic/superhydrophilic (SHPo/SHPi) patterned surfaces can be applied in various fields such as boiling heat transfer and water harvesting, many techniques for their fabrication have been developed. A patterned surface in nature generally has three-dimensionally curved surfaces, such as those observed in the banana leaf and Namib desert beetle. However, existing patterned surface fabrication technologies have a limitation in that they can be applied only to flat surfaces because they are based on laser and ultraviolet techniques. In this study, we proposed a SHPo/SHPi patterning method that can be applied to the fabrication of three-dimensional objects using aluminum. The novelty of the method is the fact that the surface coated to achieve SHPo properties does not cause a chemical reaction with the surface treatment solution. A patterned surface with a contact angle of < 10° for the SHPi surface and > 160° for the SHPo surface was successfully realized. Furthermore, this method enabled desired patterning even in areas that laser light cannot reach, such as the inner walls of a tube. This study allows the expansion of the application scope of the SHPo/SHPi surface patterning technique toward the fabrication of three-dimensional structures, thereby overcoming the limitation of previous patterned surface fabrication technologies.

Chiral Plasmonic Nanowaves by Tilted Assembly of Unidirectionally Aligned Block Copolymers with Buckling-Induced Microwrinkles.

Chiral-structured nanoscale materials exhibit chiroptical properties with preferential absorptions of circularly polarized light. The distinctive optical responses of chiral materials have great potential for advanced optical and biomedical applications. However, the fabrication of three-dimensional structures with mirrored nanoscale geometry is still challenging. This study introduces chiral plasmonic nanopatterns in wavy shapes based on the unidirectional alignment of block copolymer thin films and their tilted transfer, combined with buckling processes. The cylindrical nanodomains of polystyrene-block-poly(2-vinylpyridine) thin films were unidirectionally aligned over a large area by the shear-rolling process. The aligned block copolymer thin films were transferred onto uniaxially prestrained polydimethylsiloxane films at certain angles relative to the stretching directions. The strain was then released to induce buckling. The aligned nanopatterns across the axis of the formed microwrinkles were selectively infiltrated with gold ions. After reduction by plasma treatment, chiral plasmonic nanowave patterns were fabricated with the presence of mirror-reflected circular dichroism spectra. This fabrication method does not require any lithography processing or innately chiral biomaterials, which can be advantageous over other conventional fabrication methods for artificial nanoscale chiral materials.

Estimation of the compression strength and surface roughness of the as-built SLS components using weibull distribution

Selective laser sintering (SLS) is a process of fabrication of three-dimensional structures by fus- ing powder particles using a guided laser source. The uncertainty in the mechanical properties of the SLS parts fabricated at the same time and with the same process parameters can affect the repeatability of the SLS process. A vast difference in the mechanical properties of the concurrently processed parts can lower the production quality of the batch. Therefore, the param- eters are required to be design based on the most probable outcome of the desired properties. Weibull distribution is one such statistical-based probability distribution method to measure the likelihood of the occurrence of a value of any random variable falling within a particular range of values. Here, the Weibull distribution was used to measure the relative likelihood (90% probability) of the surface roughness and the compressive strength values of the SLS-built polyamide PA2200 components in the given sample space that was obtained from 20 random samples. The results show that the variance in the surface roughness (scan and built plane) and the compressive strength values were in the range of 6–7 μm and around 10 MPa, respectively. Moreover, the surface roughness of the two orthogonal planes with 90% reliability was measured at 14.81 μm (scan plane) and 12.15 μm (built plane). Similarly, the yield strength and the compressive strength with 90% reliability were found 25.87 MPa and 62.64 MPa, respectively.

Additive manufacturing of polymer-based structures by extrusion technologies

Abstract Extrusion-based additive manufacturing (AM) enables the fabrication of three-dimensional structures with intricate cellular architectures where the material is selectively dispensed through a nozzle or orifice in a layer-by-layer fashion at the macro-, meso-, and micro-scale. Polymers and their composites are one of the most widely used materials and are of great interest in the field of AM due to their vast potential for various applications, especially for the medical, military, aerospace, and automotive industries. Because architected polymer-based structures impart remarkably improved material properties such as low density and high mechanical performance compared to their bulk counterparts, this review focuses particularly on the development of such objects by extrusion-based AM intended for structural applications. This review introduces the extrusion-based AM techniques followed by a discussion on the wide variety of materials used for extrusion printing, various architected structures, and their mechanical properties. Notable advances in newly developed polymer and composite materials and their potential applications are summarized. Finally, perspectives and insights into future research of extrusion-based AM on developing high-performance ultra-light materials using polymers and their composite materials are discussed.

Improved development procedure to enhance the stability of microstructures created by two-photon polymerization

Natural functional surfaces often rely on unique nano- and micropatterns. To mimic such surfaces successfully, patterning techniques are required that enable the fabrication of three-dimensional structures at the nanoscale. It has been reported that two-photon polymerization (TPP) is a suitable method for this. However, polymer structures fabricated by TPP often tend to shrink and to collapse during the fabrication process. In particular, delicate structures suffer from their insufficient mechanical stability against capillary forces which mainly arise in the fabrication process during the evaporation of the developer and rinsing liquids. Here, we report a modified development approach, which enables an additional UV-treatment to post cross-link created structures before they are dried. We tested our approach on nanopillar arrays and microscopic pillar structures mimicking the moth-eye and the gecko adhesives, respectively. Our results indicate a significant improvement of the mechanical stability of the polymer structures, resulting in fewer defects and reduced shrinkage of the structures.

Rapid fabrication of three-dimensional structures for dielectrophoretic sorting of lipid-containing organisms

In this work, we demonstrate a microfluidic particle sorter consisting of three-dimensional, conducting microposts. Our sorter uses dielectrophoresis (DEP) to sort high- and low-lipid phenotypes of the yeast Yarrowia lipolytica. Y. lipolytica is one of the many microorganisms being explored as a hydrocarbon source for biodiesel, Omega-3 additives, and other products derived from fatty acids. A rapid, non-destructive, lipid-based sorting tool would accelerate the commercialization of these products. Our device consists of an array of 105, 25 μm wide gold microposts that span the height of a 15 μm channel. This array generates an electric field in a microfluidic device that is uniform through the channel height, but has a custom-shaped non-uniformity in the horizontal directions. This is crucial in order to achieve continuous sorting using DEP, as it ensures all cells are exposed to the same conditions throughout the channel height. By using very low currents (100 μA), we are able to electroplate these post arrays in fewer than 15 min. This is an order of magnitude improvement over previous reports of electroplated microstructures. With an applied signal of 250 MHz, 2.6 Vpp in our device, we separate a heterogeneous population with a purity of 97.8% in the low-lipid stream and 71.4% in the high-lipid stream. The high-lipid stream purity can be improved by adjusting the spacing of the array. This unique protocol for the rapid fabrication of 3D microstructures has enabled the creation of a non-invasive sorting tool for genetically engineered, lipid-producing organisms. The ability to screen organisms based on lipid content will alleviate one of the major bottlenecks in commercialization of microbial biofuels.

Two-photon polymerization of a branched hollow fiber structure with predefined circular pores

Porous fiber structures are of great concern to many fields of life-science engineering, but require a complex assembly processes that have geometric constraints. For this reason, tremendous efforts were expended in recent years to develop micro-/nano fabrication techniques. We report on the 3D structuring of a 3.5 mm long branched hollow fiber with 150 μm outer diameter and predefined circular pores (diameter: 30 μm). The investigated process is based on two-photon polymerization (2PP) of the UV curing resin OrmoComp®. The incident light of a femtosecond pulsed laser at 790 nm wavelength is used to generate the structure. Utilizing the non-linear behavior of two-photon absorption due to a tightly focused, high-intensity laser beam allows the local fabrication of three-dimensional structures in the photoresist. Voxels fabricated by 2PP are studied by controlling average laser power and exposure time. The appropriate average pulse energy and writing speed are determined to apply the optimal exposure parameters concerning the geometric accuracy and overall quality of the structure. The 2PP direct laser writing process is employed to generate the hollow fiber at an average laser power of 105 mW, and a writing speed of 5.0 mm/s. Water flowing through the fiber provides evidence that the core is hollow.

Direct-Write, Self-Aligned Electrospinning on Paper for Controllable Fabrication of Three-Dimensional Structures.

Electrospinning, a process that converts a solution or melt droplet into an ejected jet under a high electric field, is a well-established technique to produce one-dimensional (1D) fibers or two-dimensional (2D) randomly arranged fibrous meshes. Nevertheless, the direct electrospinning of fibers into controllable three-dimensional (3D) architectures is still a nascent technology. Here, we apply near-field electrospinning (NFES) to directly write arbitrarily shaped 3D structures through consistent and spatially controlled fiber-by-fiber stacking of polyvinylidene fluoride (PVDF) fibers. An element central to the success of this 3D electrospinning is the use of a printing paper placed on the grounded conductive plate and acting as a fiber collector. Once deposited on the paper, residual solvents from near-field electrospun fibers can infiltrate the paper substrate, enhancing the charge transfer between the deposited fibers and the ground plate via the fibrous network within the paper. Such charge transfer grounds the deposited fibers and turns them into locally fabricated electrical poles, which attract subsequent in-flight fibers to deposit in a self-aligned manner on top of each other. This process enables the design and controlled fabrication of electrospun 3D structures such as grids, walls, hollow cylinders, and other 3D logos. As such, this technique has the potential to advance the existing electrospinning technologies in constructing 3D structures for biomedical, microelectronics, and MEMS/NMES applications.

Optimal design of a 3D-printed scaffold using intelligent evolutionary algorithms

Fabrication of three-dimensional structures has gained increasing importance in the bone tissue engineering (BTE) field. Mechanical properties and permeability are two important requirement for BTE scaffolds. The mechanical properties of the scaffolds are highly dependent on the processing parameters. Layer thickness, delay time between spreading each powder layer, and printing orientation are the major factors that determine the porosity and compression strength of the 3D printed scaffold.In this study, the aggregated artificial neural network (AANN) was used to investigate the simultaneous effects of layer thickness, delay time between spreading each layer, and print orientation of porous structures on the compressive strength and porosity of scaffolds. Two optimization methods were applied to obtain the optimal 3D parameter settings for printing tiny porous structures as a real BTE problem. First, particle swarm optimization algorithm was implemented to obtain the optimum topology of the AANN. Then, Pareto front optimization was used to determine the optimal setting parameters for the fabrication of the scaffolds with required compressive strength and porosity. The results indicate the acceptable potential of the evolutionary strategies for the controlling and optimization of the 3DP process as a complicated engineering problem.

Biomimetic materials design for cardiac tissue regeneration

Cardiovascular disease is the leading cause of death worldwide. In the absence of sufficient numbers of organs for heart transplant, alternate approaches for healing or replacing diseased heart tissue are under investigation. Designing biomimetic materials to support these approaches will be essential to their overall success. Strategies for cardiac tissue engineering include injection of cells, implantation of three-dimensional tissue constructs or patches, injection of acellular materials, and replacement of valves. To replicate physiological function and facilitate engraftment into native tissue, materials used in these approaches should have properties that mimic those of the natural cardiac environment. Multiple aspects of the cardiac microenvironment have been emulated using biomimetic materials including delivery of bioactive factors, presentation of cell-specific adhesion sites, design of surface topography to guide tissue alignment and dictate cell shape, modulation of mechanical stiffness and electrical conductivity, and fabrication of three-dimensional structures to guide tissue formation and function. Biomaterials can be engineered to assist in stem cell expansion and differentiation, to protect cells during injection and facilitate their retention and survival in vivo, and to provide mechanical support and guidance for engineered tissue formation. Numerous studies have investigated the use of biomimetic materials for cardiac regeneration. Biomimetic material design will continue to exploit advances in nanotechnology to better recreate the cellular environment and advance cardiac regeneration. Overall, biomimetic materials are moving the field of cardiac regenerative medicine forward and promise to deliver new therapies in combating heart disease.

Electrodeless dielectrophoretic concentrator for analyte pre-concentration on poly-silicon nanowire field effect transistor

The sensitivity of biosensors can be affected by mass transport limitations as a result of miniaturization. To enhance signal sensitivity, pre-concentration of deoxyribonucleic acid (DNA), in the vicinity of the sensing elements of n-type polycrystalline silicon nanowire field effect transistor (Poly-Si NWFET) is demonstrated using a microfluidic device based on insulator or gradient dielectrophoresis (iDEP) to overcome mass transport limitations. In insulator-based dielectrophoresis (iDEP), insulating microstructures produce non-uniform electric fields to drive dielectrophoresis (DEP) in microsystems. Fabrication of accurately controlled three-dimensional (3D) microstructure of poly (ethylene glycol) diacrylate (PEG-DA) with a narrow microchannel using maskless gray-scale lithography is described. The fabrication of three-dimensional structures at low cost with saving time is accomplished by the use of maskless exposure system. PEG-DA has been used due to its excellent biocompatibility and ease of fabrication. To enhance the stability of PEG-DA, we added another polymer pentaerythritol tetraacrylate (PETA). Electrical property of the Poly-Si NWFET is ensured by plotting I–VG curve after the integration of iDEP micro device.

10213 溶解性モールドを用いたインプリントによる3次元表面複合材料の創製(OS3-3【高分子系複合材料の成形と力学特性(3)】)

10213 溶解性モールドを用いたインプリントによる3次元表面複合材料の創製(OS3-3【高分子系複合材料の成形と力学特性(3)】)

Development of a micro cell compression stimulator for evaluating real-time cellular responses

This paper presents a micro cell compression stimulator for evaluating real-time cellular responses to compression stimuli. The device was produced by a micro three-dimensional structure fabrication process using multiple exposures to the photoresist. The device consists of a pressure inlet port, cell inlet ports, a gasket, microchannels, cell culture chambers, and a diaphragm on the culture chamber for applying compressive pressure to cells. Compression stimuli applied to the cells can be controlled by regulating the expansion of the diaphragm via a pressure control. The device permits the observation of cellular responses to compressive pressure in real time because it is made of transparent materials and stimulates the cells without deforming the cell culture surface, when observed by optical microscopy. We demonstrated the validity of the fabrication process, evaluated the performance of the fabricated device, and compared the experimental results with the FEM structural analysis results. We found through operational testing that the diaphragm was deformed quickly by applying negative/positive pressure and that the diaphragm displacement became larger with increasing applied pressure. These results indicate that this device can be used to control the intensity and the cell stimulus profile by regulating the applied pressure. In all cases, the cellular deformation during compression stimulus was successfully observed in real time using an optical microscope. The device is expected to facilitate the control of stem cell differentiation and the clarification of cellular mechanoreceptor mechanisms and signal transduction pathways.

Residual-layer-free direct printing by selective filling of a mould

We have developed a residual-layer-free patterning method by selectively filling the concavity of a mould with liquid solution. The method has potential for large-area roll-to-roll fabrication of micro-devices on the flexible substrates. By choosing an appropriate solution or liquid, such as polymethylmethacrylate (PMMA) solution or epoxy precursor, with suitable dynamic contact angle on the SAM-treated mould, the liquid can be coated on the concavity of the mould only. By using this method, residual-layer-free epoxy pattern could be achieved without the need of an extra step. Without forming a residual layer, the technology could simplify the fabrication of three-dimensional structures with low distortion and smooth edges. Conductive PPy/PMMA patterns can also be fabricated by selective deposition of PMMA/FeCl3 and then exposing to pyrrole/chlorobenzene vapours to induce chemical oxidative polymerization of PPy. The electrical resistivity of PPy/PMMA obtained was 0.17 Ω cm.

Fabrication of three-dimensional structures for the assessment of cell mechanical interactions within cell monolayers

The measurement of the forces at play in cell/cell adhesion uses a cell monolayer plated onto two-dimensional substrate like arrays of elastomeric microfabricated pillars. Unfortunately, the few attempts that have been done in this direction do not mimic the extracellular environment and lack knowledge on the correlation between the various types of cellular adhesions. Here, the authors suggest using a new experimental setup that more accurately simulates the three-dimensional (3D) environment of cells in tissues, using stretchable hexagonal monocellular 3D structures. The present article shows a way of fabricating these hexagonal biosensors, which are open structures made of biocompatible elastomeric polydimethylsiloxane (PDMS). The novelty of the whole fabrication process of these 3D PDMS structures consists in the use of a sacrificial silicon mold. An original mechanical PDMS planarization process is proposed. This article also describes a strategy for a selective functionalization of the 3D structure sidewalls where the cells must adhere.

Two-photon polymerization of titanium-containing sol–gel composites for three-dimensional structure fabrication

In this work, we have synthesized and characterized a novel, titanium-containing hybrid material that can be structured three-dimensionally using two-photon polymerization. We investigate the effect on the structurability of the increase of titanium isopropoxide and methacrylic acid in this photosensitive composite. We show that while it is possible to make transparent thin films with a titanium isopropoxide molar content as high as 90%, three-dimensional structures can be made only when the titanium isopropoxide molar content is less than 50%. We measure the refractive index of films with different titanium isopropoxide: methacrylic acid concentrations and we show that while the refractive index increases linearly with the titanium isopropoxide, the increase of the methacrylic acid content does not affect the refractive index of the material.

Nanoimprint Lithography for Functional Three‐Dimensional Patterns

Nanoimprint lithography (NIL) is viewed as an alternative nanopatterning technique to traditional photolithography, allowing micrometer-scale and sub-hundred-nanometer resolution as well as three-dimensional structure fabrication. In this Research News article we highlight current activities towards the use of NIL in patterning active or functional materials, and the application of NIL in patterning materials that present both chemistry and structure/topography in the patterned structures, which provide scaffolds for subsequent manipulation. We discuss and give examples of the various materials and chemistries that have been used to create functional patterns and their implication in various fields as electronic and magnetic devices, optically relevant structures, biologically important surfaces, and 3D particles.