Table 1 - uploaded by Adriano J. G. Otuka
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Glass transition temperature (T g ), cutoff wavelength (λ cutof ), threshold pulse energy (E th ) threshold intensity (I th ) to damage the sample surface.
Source publication
Novel materials have been developed to meet the increasing mechanical, electrical and optical properties required for technological applications in different fields of sciences. Among the methods available for modifying and improving materials properties, femtosecond laser processing is a potential approach. Owing to its precise ablation and modifi...
Contexts in source publication
Context 1
... glass transition temperatures obtained from the DSC curves are shown in Table 1. Figure 3 shows the absorption spectra of the copper doped borate (solid line) and borosilicate (dashed line) glasses. ...
Context 2
... absorption band around 800 nm is attributed to the superposition of 2 B 1g → 2 A 1g and 2 B 1g → 2 B 2g electronic transitions 10. The spectra shown in Figure 3 are quite similar, in which small differences are observed for the absorption band intensity at visible region and in the cutoff wavelength, presented in Table 1. Such differences are related to the distinct compositions of the glass matrix. ...
Citations
... In the literature, TPP is also described as two-photon-absorbed photopolymerization [16,21], two-photon induced polymerization Fig. 1. Schematic of different lithography approaches to generate microstructures in 2, 2.5, 3 and 4 dimensions, a) conventional 2D photolithography, producing 2D structures of identical heights; b) gray-tone photolithography for creating non-freestanding 2.5D structures with different heights; c) two-photon polymerization approach with two different possible writing methods (Direct Laser Writing DLW, and Dip-in Laser Lithography DiLL) to fabricate 3D tiny structures; and d) 4D lithography 3D structures made of materials responding to an external stimulus. ...
In the last decades, additive manufacturing (AM), also called three-dimensional (3D) printing, has advanced micro/nano-fabrication technologies, especially in applications like lightweight engineering, optics, energy, and biomedicine. Among these 3D printing technologies, two-photon polymerization (TPP) is the technique which offers the highest resolution (even at the nanometric scale), reproducibility and the possibility to create monolithically 3D complex structures with a variety of materials (e.g. organic and inorganic, passive and active). Such active materials change their shape upon an applied stimulus or degrade over time at certain conditions making them dynamic and reconfigurable (also called 4D printing). This is particularly interesting in the field of medical microrobotics as complex functions such as gentle interactions with biological samples, adaptability when moving in small capillaries, controlled cargo-release profiles, and protection of the encapsulated cargoes are required. Here we review the physics, chemistry and engineering principles of TPP, with some innovations that include the use of micromolding and microfluidics, and explain how this fabrication scheme provides the microrobots with additional features and application opportunities. The possibility to create microrobots out of multiple smart materials and to incorporate nano- and biomaterials for in situ chemical reactions, biofunctionalization, or imaging is put into perspective. We categorize the microrobots based on their motility mechanisms, function, and architecture, and finally discuss the future directions in this field.
... They may decrease the microlens surface quality. 14 One of the disadvantages in micromachining microlens is that it often requires expensive high precision machine tools. Furthermore, the machined microlens surfaces usually need to be extensively polished to remove the residual tool marks left by the machine tools. ...
We present an efficient fabrication technique for a glass microdome structure (GMDS) based on the microthermal expansion principle, by inflating the microcavities confined between two thin glass slides. This technique allows controlling the height, diameter, and shape of the GMDS with a uniformity under 5%. The GMDS has a high potential for the application of the microlens and lens array. This inflated hollow, thin glass structure is stable at extreme environments such as in strong acid and high temperature conditions. More importantly, the hollow microdome can be filled with liquid substances to further extend its applications. To verify our method, various GMDSs were fabricated under different process conditions, at different temperatures (540 °C–600 °C), microcavity diameters (300 μm–600 μm), glass thicknesses (120 μm–240 μm), and microcavity etching depths (25 μm–70 μm). The optical features of “empty” and “filled” microcavities were investigated. An empty microcavity functioned as a reducing lens (0.61×–0.9×) (meniscus lens), while a filled microcavity functioned as a magnifying lens (1.31×–1.65×) (biconvex lens). In addition, both lenses worked in strong acid (sulfuric acid) and high temperature (over 300 °C) conditions in which other materials of lenses cannot be used.
... In 2013, B. K. Nayak et al. reported a method that superhydrophobic surfaces were fabricated by replicating micro/nano structures on to poly(dimethylsiloxane) (PDMS) from a replication master made by ultrafast-laser machining [161]. No additional coating was required on the PDMS to realise a contact angle greater than 154 • . ...
Micro/nano structures have unique optical, electrical, magnetic, and thermal properties. Studies on the preparation of micro/nano structures are of considerable research value and broad development prospects. Several micro/nano structure preparation techniques have already been developed, such as photolithography, electron beam lithography, focused ion beam techniques, nanoimprint techniques. However, the available geometries directly implemented by those means are limited to the 2D mode. Laser machining, a new technology for micro/nano structural preparation, has received great attention in recent years for its wide application to almost all types of materials through a scalable, one-step method, and its unique 3D processing capabilities, high manufacturing resolution and high designability. In addition, micro/nano structures prepared by laser machining have a wide range of applications in photonics, Surface plasma resonance, optoelectronics, biochemical sensing, micro/nanofluidics, photofluidics, biomedical, and associated fields. In this paper, updated achievements of laser-assisted fabrication of micro/nano structures are reviewed and summarized. It focuses on the researchers’ findings, and analyzes materials, morphology, possible applications and laser machining of micro/nano structures in detail. Seven kinds of materials are generalized, including metal, organics or polymers, semiconductors, glass, oxides, carbon materials, and piezoelectric materials. In the end, further prospects to the future of laser machining are proposed.
... In the field of optics and photonics, silk fibroin-based films have prompted as interesting optical materials because of their transparency from the visible to the near infrared, which favors the development of several devices, such as 3D photonic crystals [19,20], diffraction gratings [21,22], plasmonic structures [23] and optical waveguides [24][25][26][27]. At the same time, femtosecond direct laser writing (fs-DLW) has proven to be an important method for material´s processing, enabling the fabrication of optical devices in a wide variety of materials, being useful for the obtainment of optical waveguides, microfluidic channels, and 3D flexible electronic circuits [28][29][30][31][32]. In this method, the high intensity of the laser beam deposits enough energy on the material, causing a permanent change in the micrometer scale, while reducing thermal effects. ...
Silk fibroin is an abundant natural polymer, which in the last years has been proposed as an attractive material for high-technological applications, offering also new opportunities for photonics and optoelectronics. In this context, the design of optical waveguides based on silk fibroin is of great interest because of their ability to direct light in a controlled manner. In this work, we demonstrate the use of femtosecond direct laser writing (fs-DLW) to fabricate silk fibroin waveguides. Such waveguides were characterized by coupling 632.8 nm light from a He–Ne laser. Our findings demonstrate the potential of fs-DLW as a novel approach for the fabrication of silk fibroin waveguides, which provides a versatile platform for optical and biomedical applications.
... The femtosecond plasma is applied for highly localized material processing, including precision microfabrication [11,12], laser writing [13] and other emerging applications [14], nanoparticles fabrication [15][16][17] and laser induced breakdown spectroscopy [18]. Moreover, femtosecond lasers have been widely used in retinal microsurgery (LASIK) and numerous medical applications, where accurate cutting or tissue ablation is required [19,20]. ...
Development of alternative methods for hydrogen production from liquid water requires novel research approaches. In the present study, we investigated the yet unexplored method of water splitting by femtosecond laser pulses (100 fs, λ = 800 nm) focused into a quartz cell containing ultra-purified water. As a result of plasma-induced radical reactions, the formation of stable products including molecular H2 and H2O2 was identified and quantified as a function of irradiation time, repetition rate and pulse energies up to 1 mJ. The observed dependencies provided new insight into the basic chemical processes taking place in the plasma generated in water by focused laser pulses. It was found that the energy efficiency of hydrogen production increased with the decrease of pulse energy and repetition rate. Under appropriate irradiation conditions, an advantageous stoichiometry of water decomposition only into pure H2 and H2O2 (without O2 ) was achieved. An original way of process intensification (a series of separate laser beams of adequately low energy generating plasma at different places, a sufficiently fast water flow through the irradiation zones) was proposed in order to improve the energy yield of hydrogen generation and to ensure the evolution of pure hydrogen as the only gaseous product of the water splitting. Taking into account the suggested solution, the predicted energy efficiency of hydrogen production of 0.4 g H2/kWh was found to be comparable to other plasma methods for H2 generation. Our results show that direct production of pure H2 using femtosecond laser pulses is a fully reasonable process that carries considerable potential for both research and application.
... Markings must satisfy certain technological criteria, such as visibility, legibility, durability or laser markability [42][43][44][45], but marking speed (cycle time) is also a basic criterion in industrial applications. During laser marking of thermoplastics, various interactions take place in the polymer, some of which are hardly known as the pulse time of the laser can be measured in µs, ns, ps or fs [46][47][48][49][50][51], but the temperature during marking can reach up to 800°C [8]. Thermoplastics without fillers or pigments can be divided into three main groups according to their suitability for laser marking: 379 Laser markability of PVC coated automotive electric cables E. Bitay * Sapientia Hungarian University of Transylvania, Faculty of Technical and Human Sciences, 540485 Târgu-Mureş, Op. 9., Cp. 4., Romania - Members of group 1 absorb laser rays well, therefore they are carbonized and the marking will be dark. ...
This article describes the test results for laser markability of automotive electrical cables. The insulation is PVC, but the colour and construction of the insulations are different. Two types of laser workstations were used, one with a wavelength of 1064 nm and another with 532 nm. The penetration depth of the laser beam was determined by optical microscopy on cross sections. The 1064 nm laser beam can mark all investigated materials with good contrast, except the yellow insulation. The 532 nm laser beam with fast speed can hardly produce contrast with any of the materials. The laser markability of the yellow insulation was found to be the most problematic. On the two-layer insulation, despite the whitening of the inner material, dark marking is produced because the heat developing on the interface of the two layers will heat up and carbonize the transparent layer.
... They may decrease the microlens surface quality. 14 One of the disadvantages in micromachining microlens is that it often requires expensive high precision machine tools. Furthermore, the machined microlens surfaces usually need to be extensively polished to remove the residual tool marks left by the machine tools. ...
4-step micro glass blowing method for all glass lens array fabrication.
... Femtosecond laser has also been applied to produce active microstructures via two-photon absorption polymerization (2PP). This technique enables the fabrication of neat and doped polymeric microstructures with high definition and virtually no shape constraints, finding application in optical, electrical and biological devices [59][60][61][62][63][64]. For instance, [65] the fabrication of three-dimensional microstructures based on triacrylate monomers and ZnO nanowires using a fs-laser experimental setup delivering pulse energies of 0.5 nJ has been reported. ...
... The inset of Figure 6 shows the fluorescence (top view) image of such a ZnO nanowires/polymer composite microstructure containing 5 wt % of ZnO nanowires, which was excited using a cw laser at 350 nm. Two-photon polymerization was also employed by Otuka et al. [59] to fabricate concentric cylindrical polymeric shells using a multi-step fabrication process. The outer cylindrical shell was composed by undoped acrylic resin, while the inner one was composed of the same acrylic resin doped with Rhodamine B. Figure 7a displays a scanning electron microscopy image of such structure (top view), while (b) and (c) display optical and fluorescence microscopy images respectively. ...
... In (b) it is possible to observe parts of the cylindrical structure; the center with air, the inner cylindrical shell doped with Rhodamine B and the outermost with net polymer. This Two-photon polymerization was also employed by Otuka et al. [59] to fabricate concentric cylindrical polymeric shells using a multi-step fabrication process. The outer cylindrical shell was composed by undoped acrylic resin, while the inner one was composed of the same acrylic resin doped with Rhodamine B. (top view), while (b) and (c) display optical and fluorescence microscopy images respectively. ...
The current demand for fabricating optical and photonic devices displaying high performance, using low-cost and time-saving methods, prompts femtosecond (fs)-laser processing as a promising methodology. High and low repetition femtosecond lasers enable surface and/or bulk modification of distinct materials, which can be used for applications ranging from optical waveguides to superhydrophobic surfaces. Herein, some fundamental aspects of fs-laser processing of materials, as well as the basics of their most common experimental apparatuses, are introduced. A survey of results on polymer fs-laser processing, resulting in 3D waveguides, electroluminescent structures and active hybrid-microstructures for luminescence or biological microenvironments is presented. Similarly, results of fs-laser processing on glasses, gold and silicon to produce waveguides containing metallic nanoparticles, analytical chemical sensors and surface with modified features, respectively, are also described. The complexity of fs-laser micromachining involves precise control of material properties, pushing ultrafast laser processing as an advanced technique for micro/nano devices.
... An illumination source and a CCD camera allow for real time monitoring of the polymerization. This experimental apparatus is described in details elsewhere [22,23]. After polymerization, the sample is immersed in ethanol to wash away the uncured resin, leaving on the substrate only the fabricated microstructures. ...
Studies of cell development in artificial microenvironments can contribute to understanding a series of physiological mechanisms that might be influenced by geometrical features of the microenvironment itself. In this work we applied two-photon polymerization to fabricate three-dimensional microenvironments composed of a matrix arrangement of microstructures (circular and square cross-sections pillars) with distinct spacing. Such microenvironments were used to evaluate the growth of Michigan Cancer Foundation-7 (MCF-7) cells that are commonly used as a model system to investigate fundamental aspects of the tumor biology. Our results reveal that the cell density decreases as the distance between structures in the environment is increased. Additionally, cell growth shows slightly better results for the microenvironments composed of circular cross-section structures.
Additive micro/nano‐manufacturing of polymeric precursors combining with a subsequent pyrolysis step enables the design‐controlled fabrication of micro/nano‐architected 3D pyrolytic carbon structures with complex architectural details. Pyrolysis results in a significant geometrical shrinkage of the pyrolytic carbon structure, leading to a structural dimension significantly smaller than the resolution limit of the involved additive manufacturing technology. Combining with the material properties of carbon and 3D architectures, architected 3D pyrolytic carbon exhibits exceptional properties, which are significantly superior to that of bulk carbon materials. This article presents a comprehensive review of the manufacturing processes of micro/nano‐architected pyrolytic carbon materials, their properties, and corresponding demonstrated applications. Acknowledging the “young” age of the field of micro/nano‐architected carbon, this article also addresses the current challenges and paints the future research directions of this field.
