Fabrication Of Periodic Microstructures Research Articles

Scanner‐Based Direct Laser Interference Patterning on Stainless Steel

Direct laser interference patterning (DLIP) so far has been used almost exclusively in combination with mechanical translation stages reaching impressive throughputs for very specific configurations. As an alternative, DLIP modules can be combined with laser scanners, however presenting some limitations in comparison with standard static optical setups due to the limited possible spatial separation between the interfering beams. Herein, the fabrication of periodic microstructures on stainless steel using a galvanometer‐scanner DLIP approach is addressed. Line‐like patterns with spatial periods ranging from 2.9 to 12.8 μm are produced using a nanosecond pulsed laser source operating at a wavelength of 527 nm. The scan fields generated are evaluated with respect to the structure quality and scan field size, with dependence on the spatial period. Furthermore, the correlation between the spatial period, laser fluence, total number of pulses, and resulting structure depth of the line‐like patterns is discussed. In addition, the optimization of process parameters leads to surface patterns with aspect ratios greater than 1. The achievable structuring speeds are determined under consideration of the used number of pulses. Finally, throughputs up to 7.69 cm2 min−1 with less than 0.5 W laser power at a repetition rate of 3.5 kHz are realized.

Influence of roughness achieved by periodic structures on the wettability of aluminum using direct laser writing and direct laser interference patterning technology

The fabrication of periodic microstructures on pure aluminum is studied in this work. Triangular and pillar-like structures are manufactured using nanosecond pulsed direct laser writing (DLW) and picosecond pulsed direct laser interference patterning (DLIP), respectively. By varying the process parameters (laser fluence, pulse to pulse overlap, pattern size and geometry) structures with different depths and corresponding roughness parameters are produced. Finally, the influence of the various resultant morphological parameters on the wettability properties of the fabricated structures is investigated by means of static contact angle measurements. Two different behaviors are observed with respect to the long term wetting properties depending on the used laser method. The topography of the treated surfaces is characterized using confocal microscopy and scanning electron microscopy, while contact angle measurements are performed with a drop shape analyzer. Surface chemistry is analysed by X-Ray photoelectron spectroscopy.

Minimizing Burrs and Defects on Microstructures with Laser Assisted Micromachining Technology

Molding technology is widely used to manufacture optical components because of its high efficiency. Along with the quick development of miniaturization in industry, the detrimental effects of previously negligible burrs and defects on mold surfaces have become significant to the performance of components, so these problems should be minimized. In this study, a laser assisted micromachining method was developed to solve this problem during the fabrication of periodic microstructures on a molding material of electroless nickel-phosphorus (NiP) plating. The transient temperature distributions of the workpiece under laser irradiation and the change in the maximum shear stress during the laser assisted micromachining process were simulated to set appropriate experimental conditions. Then, periodic micropyramid structures were fabricated by both conventional cutting and the laser assisted cutting processes. Results show that defects largely decreased on machined structures with the assistance of laser irradiation. The decrease in specific cutting force and the change of chips’ morphology were also utilized to analyze the reasons for this improvement.

Fabrication of Periodic Microstructures on Nickel Template by Multi-Beam Laser Interference

Complex microstructures can be fabricated on nickel template directly by femtosecond laser. But the efficiency is low and much time is inevitable when large scale microstructures are fabricated. The multi-beam interference provides an effective method for fabrication of large scale microstructures. This paper mainly focuses on direct ablation of nickel template by four-beam interference and fabricating periodic microstructures by laser interference lithography. Experimental results show that submicron periodic stripes and column structures can be produced on the nickel template by laser interference, laying the foundation of making nickel molds for microfluidic chips.

Fabrication of periodic micro-structures by holographic lithography

Fabrication of periodic micro-structures by holographic lithography

Fabrication of periodic micro-structures by holographic lithography

The principles of the holographic lithography technique are reviewed, and the ability in the formation of structures with different periods by the holographic lithography technique in SZ2080 is demonstrated. The influence of laser exposure, phase shift between interfering laser beams, and the used laser wavelength on the structures fabricated by the four-beam interference technique has been studied. It is shown that by using the − interfering beams with a different phase is it possible to reduce the period of the structure √2 times compared to the four interfering beams of the same phase. Fabrication of micro-structures by the holographic lithography technique can be realized via multi-photon and single-photon polymerization processes. The structures created by these two techniques are compared. Finally, in the experiments with the five-beam interference, the doubleperiod effect was observed by adding the zero-order beam with a low intensity. The fabricated periodic microstructures have the potential to be used as a scaffold for cell growth and micro-optics.

Supramolecular Chiral Structures: Smart Polymer Organization Guided by 2D Polarization Light Patterns

AbstractChiral periodic structures and photonic crystals have attracted a great deal of interest due to their applications in advanced photonics. As a consequence, the design and the fabrication of periodic microstructures in photosensitive materials have been widely investigated. Many achievements in the fabrication of such devices have been made over the last decade, but most of the established methods are still restricted to light intensity distribution with different structural shapes and minor attention has been devoted to exploit the vectorial nature of the light coupled with the response of polarization sensitive materials. Here, supramolecular chiral structuring in an amorphous azo‐polymer is demonstrated, coupling the strong and diversified photoresponse of the material with the holographic recording of 2D polarization patterns. The smart polymer organization guided by the complex light field induces periodic chiral microstructures, with spiral‐ or ribbon‐like shape and identical or opposite helicity, characterized by high stability and complete reconfigurability. The holographic structures are theoretically described by means of the Jones matrix method and experimentally investigated, confirming the simultaneous presence of both linear and circular photoinduced anisotropies. These results prove an alternative approach to design a new class of materials with periodic chiral arrangement.

Fabrication of Periodic Micro-Structures by Multi-Photon Polymerization Using the Femtosecond Laser and Four-Beam Interference

Multi-photon polymerization by interference is a promising technique for mass fabrication of 3D periodic micro-structures over large areas, which can be used in various fields such as biomedicine (cell growing), photonics (photonics crystals), etc. As direct laser writing approach is a relatively slow process, fabrication of periodic structures by interference field of a few laser beams can be a significantly faster alternative route of parallel processing. The periodic structures are produced by the single laser exposure over the whole irradiated area. In this paper we present examples how periodic micro-structures can be fabricated over a large area by multi-photon polymerization in a negative photopolymer SZ2080 (ORMOSIL) using four-beam interference of a femtosecond laser.http://dx.doi.org/10.5755/j01.ms.17.3.587

Fabrication of periodic microstructures by holographic photopolymerization with a low-power continuous-wave laser of 532 nm

A ternary photopolymer system consisting of a new photoinitiator, an oligomer and a binder has been developed. Experiments show that one-, two- and three-dimensional periodic microstructures can be successfully holographically fabricated by single-photon photopolymerization with this material and a low-power (tens of mW) continuous-wave laser at 532 nm. The preparation of this material is explained and its absorption spectra are tested. The optical setup and the experimental results including the diffraction patterns verifying the formation of periodic structures are given. Compared to other methods with the use of high-power lasers, this approach is much more accessible to most laboratories and researchers and therefore may promote the use of holographic fabrication techniques for photonic crystals.