Microstereolithography Technique Research Articles

Electrically conductive scaffolds mimicking the hierarchical structure of cardiac myofibers

Electrically conductive scaffolds, mimicking the unique directional alignment of muscle fibers in the myocardium, are fabricated using the 3D printing micro-stereolithography technique. Polyethylene glycol diacrylate (photo-sensitive polymer), Irgacure 819 (photo-initiator), curcumin (dye) and polyaniline (conductive polymer) are blended to make the conductive ink that is crosslinked using free radical photo-polymerization reaction. Curcumin acts as a liquid filter and prevents light from penetrating deep into the photo-sensitive solution and plays a central role in the 3D printing process. The obtained scaffolds demonstrate well defined morphology with an average pore size of 300 ± 15 μm and semi-conducting properties with a conductivity of ~ 10–6 S/m. Cyclic voltammetry analyses detect the electroactivity and highlight how the electron transfer also involve an ionic diffusion between the polymer and the electrolyte solution. Scaffolds reach their maximum swelling extent 30 min after immersing in the PBS at 37 °C and after 4 weeks they demonstrate a slow hydrolytic degradation rate typical of polyethylene glycol network. Conductive scaffolds display tunable conductivity and provide an optimal environment to the cultured mouse cardiac progenitor cells.

Mechanical performance and defect analysis of the imperfect micro smooth gyroid cylinder shell structure

Projection micro-stereolithography (PμSL) technique has been demonstrated effective in fabricating the micro lattices. However, the complex fabrication process would inevitably yield stochastic geometric defects within the target structure. In this paper, compressive mechanical properties and deformation modes of the micro gyroid cylinder shell structure with defects originated from the PμSL process were examined through experimental test and numerical simulation. Both the synchrotron X-ray tomography (SR-μCT) investigation and interrupted in-situ compression experiment were conducted to study the role of process-induced defects on the mechanical behavior. Testing results indicated that the fabricated thickness value was much larger than the design value, which had a non-negligible effect on the mechanical properties of the gyroid cylinder shell structure. Then, the reconstructed 3D true model was proposed based on the 2D tomography images. Simulation results indicated that the true model predicted results were more consistent with the experimental results when compared with the ideal model.

Fabrication of dimensionally accurate 3D micro components by projection micro-stereolithography technique

Fabrication of dimensionally accurate 3D micro components by projection micro-stereolithography technique

Piezoelectric inkjet coating of injection moulded, reservoir-tipped microneedle arrays for transdermal delivery

Coated microneedles have significant potential for use in transdermal delivery applications. In this paper, we describe the fabrication of microneedle master templates using microstereolithography techniques and subsequently use a commercial injection moulding process to replicate these microneedles in biocompatible cyclic olefin polymer (COP) materials. Notably, the 475 μm-tall needle designs feature a shallow pit or reservoir at the tip, thereby providing both a target and holder for incoming droplets that are deposited using a piezoelectric inkjet printer. Using this design, no tilting or rotation of the needle array is required during the filling process. In the preliminary tests reported here, the reservoir is filled with a FITC-labelled dye that acts as a model drug, and ex vivo skin tests are used to verify skin penetration, the transfer of this model drug to the skin and to measure the reliability of the needles themselves. To our knowledge, this is the first time that such an inkjet-filled, reservoir-tipped microneedle has been demonstrated.

Formation of Neural Networks in 3D Scaffolds Fabricated by Means of Laser Microstereolithography.

We developed and tested new 3D scaffolds for neurotransplantation. Scaffolds of predetermined architectonic were prepared using microstereolithography technique. Scaffolds were highly biocompatible with the nervous tissue cells. In vitro studies showed that the material of fabricated scaffolds is not toxic for dissociated brain cells and promotes the formation of functional neural networks in the matrix. These results demonstrate the possibility of fabrication of tissue-engineering constructs for neurotransplantation based on created scaffolds.

Additive Manufacturing of a 3D Terahertz Gradient‐Refractive Index Lens

A 3D terahertz gradient-refractive index lens designed by transformation optics is achieved by fabricating “woodpile” structures with varying dimensions of subwavelength dielectric unit cells using the projection microstereolithography technique. Both simulation and experimental investigations confirm that the lens delivers an imaging resolution very close to the diffraction limit over a frequency range from 0.4 to 0.6 THz.

Three-dimensional printing of freeform helical microstructures: a review.

Three-dimensional (3D) printing is a fabrication method that enables creation of structures from digital models. Among the different structures fabricated by 3D printing methods, helical microstructures attracted the attention of the researchers due to their potential in different fields such as MEMS, lab-on-a-chip systems, microelectronics and telecommunications. Here we review different types of 3D printing methods capable of fabricating 3D freeform helical microstructures. The techniques including two more common microfabrication methods (i.e., focused ion beam chemical vapour deposition and microstereolithography) and also five methods based on computer-controlled robotic direct deposition of ink filament (i.e., fused deposition modeling, meniscus-confined electrodeposition, conformal printing on a rotating mandrel, UV-assisted and solvent-cast 3D printings) and their advantages and disadvantages regarding their utilization for the fabrication of helical microstructures are discussed. Focused ion beam chemical vapour deposition and microstereolithography techniques enable the fabrication of very precise shapes with a resolution down to ∼100 nm. However, these techniques may have material constraints (e.g., low viscosity) and/or may need special process conditions (e.g., vacuum chamber) and expensive equipment. The five other techniques based on robotic extrusion of materials through a nozzle are relatively cost-effective, however show lower resolution and less precise features. The popular fused deposition modeling method offers a wide variety of printable materials but the helical microstructures manufactured featured a less precise geometry compared to the other printing methods discussed in this review. The UV-assisted and the solvent-cast 3D printing methods both demonstrated high performance for the printing of 3D freeform structures such as the helix shape. However, the compatible materials used in these methods were limited to UV-curable polymers and polylactic acid (PLA), respectively. Meniscus-confined electrodeposition is a flexible, low cost technique that is capable of fabricating 3D structures both in nano- and microscales including freeform helical microstructures (down to few microns) under room conditions using metals. However, the metals suitable for this technique are limited to those that can be electrochemically deposited with the use of an electrolyte solution. The highest precision on the helix geometry was achieved using the conformal printing on a rotating mandrel. This method offers the lowest shape deformation after printing but requires more tools (e.g., mandrel, motor) and the printed structure must be separated from the mandrel. Helical microstructures made of multifunctional materials (e.g., carbon nanotube nanocomposites, metallic coated polymer template) were used in different technological applications such as strain/load sensors, cell separators and micro-antennas. These innovative 3D microsystems exploiting the unique helix shape demonstrated their potential for better performance and more compact microsystems.

Terahertz plasmonic high pass filter

Metamaterials, which contain engineered subwavelength microstructures, can be designed to have positive or negative ε and μ at desired frequencies. In this letter, we demonstrate a metamaterial which has a “plasmonic” response to electromagnetic waves in the terahertz (THz) range. The sharp change of reflection and transmission at this plasma frequency makes the structure a high pass filter. The reflection response is characterized by Fourier transform infrared spectroscopy, and a plasma frequency at 0.7 THz is observed, which agrees with the theoretical calculation. The metamaterial is a two-dimensional cubic lattice consisting of thin metal wires, having wire diameter of 30 μm, lattice constant of 120 μm, and wire length of 1 mm. The microstereolithography technique is employed to fabricate the high-aspect-ratio lattice.

Three‐Dimensional Ceramic Microcomponents Made Using Microstereolithography

The combination of a microstereolithography process and a high‐load ceramic suspension is used to produce complex three‐dimensional alumina microparts. The object (see Figure) produced is designed for microfluidic applications, but the versatility of the microstereolithography technique is generally applicable to the preparation of microcomponents for numerous applications.

Recent Progress in Three-Dimensional Microstereolithography.

In recent years, microstereolithography techniques have been used to fabricate various types of three-dimensional micro/nano devices such as microelectromechanical systems, micro total analysis systems and photonic crystals. Two-photon microstereolithography is one of the most promising methods in microstereolithography. This paper describes the fabrication principle, a fabrication system and the latest experimental results of two-photon microstereolithography. In addition, several applications of two-photon microstereolithography, including optically driven micromachines and photonic crystals, are introduced. Two-photon microstereolithography is useful for not only micro/nano technologies but also biotechnologies.

Microstereolithography: a Review

ABSTRACTMicrostereolithography is a technology at the interface of the microengineering and rapid prototyping domains. It has evolved from the stereolithography technique, and is also based on a light-induced layer-stacking manufacturing. As the resolution of the microstereolithography technique is far better than the one of rapid prototyping technologies, this technique is of particular interest in the microengineering domain where its 3D capability allows the production of components no other microfabrication technique can create.The first developments of the microstereolithography technique have started in 1993 and different research teams have developed machines since, using different approaches. This paper reviews the major microstereolithography processes developed until now.Microstereolithography is starting to be a commercially available manufacturing process. As the market for miniaturized products grows rapidly, there is an increasing need for highresolution small size prototype parts. If the production of small mechanical components is the first commercial application of microstereolithography, this technology can also produce useful components for the microrobotic, microfluidic, microsystems and biomedical fields. Current research in the microstereolithography field is focused on using ceramic composites as material to manufacture complex three-dimensional parts that can be sintered to produce pure alumina microcomponents.

Distributed MEMS phase shifters bymicrostereolithography on silicon substrates for microwave andmillimeter wave applications

A distributed microelectromechanical system (MEMS)phase shifter has been fabricated on a high-resistivity siliconsubstrate using a microstereolithography technique. Thistechnique enables us to decrease the early development cost byremoving the need for photomasks used for defining the MEMSbridges. The distributed MEMS phase shifter fabricated consistsof a high-impedance coplanar waveguide transmission lineand ten MEMS bridges of 4.5 µm height, which givesa phase shift of 6° at 18 GHz with a bias voltage of30 V. This MEMS bridge design can be improved further using themicrostereolithography technique to give a phase shift of nearly90° at 18 GHz with a bias voltage of 20 V. Thefabrication procedure described here shows significant promisefor the use of microstereolithography techniques for RF MEMSdevices for ground and space telecommunication applications.

Rapid prototyping of small size objects

The commercialization of new products integrating many functions in a small volume requires more and more often the rapid prototyping of small high‐resolution objects, having intricate details, small openings and smooth surfaces. To give an answer to this demand, the stereolithography process has started to evolve towards a better resolution: the “small spot” stereolithography technology allows to reach a sufficient resolution for the manufacturing of a large range of small and precise prototype parts. Microstereolithography, a technique with resolution about an order of magnitude better than conventional stereolithography, is studied by different academic research groups. The integral microstereolithography machine developed at the Swiss Federal Institute of Technology in Lausanne is described in this paper, and potential applications are presented. The resolutions of conventional, small spot and microstereolithography technologies are compared and the potential of the microstereolithography technique is shown for the manufacturing of small and complex objects.