Microlens arrays (MLAs) with special functions such as superhydrophobicity and self-cleaning ability are highly desired in the micro-optical system which is often used in easily polluted environment. In this paper, a new method is demonstrated to fabricate the MLAs with a high fill factor and superhydrophobicity. The method combines femtosecond laser wet etching, polydimethylsiloxane (PDMS) replication and subsequently femtosecond laser direct writing process. The fabricated MLAs decorated with micro/nanoscale hierarchical structures compared with the normal MLAs. Water droplets on the as-prepared surfaces exhibit superhydrophobicity and ultralow adhesion which endows the fabricated samples possess self-cleaning property. The as-fabricated MLAs could find their applications in bioscience research, ocean exploration, endoscopic surgery, microfluidic system, etc.
Glioma accounts for the majority of brain cancer and is the most common and aggressive human cerebral disease with low survival rates, which have received much attention on how the cancer cells can be controlled. The aim of this report is to investigate the controlling of C6 glioma cells on 3D micro/nano silicon structures with different surface energy. The silicon surface topography was formed by femtosecond laser and adjusted through changing the processing parameter. The transformation of surface energy was realized by covering a layer of organosilane with low surface tention--1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFDTS). The results showed that the fewest C6 cells adhered onto hierarchical micro-mountain structures with organosilane, which exhibited the anti-cell property, while the most C6 cells adhered onto nano-grain particle structures without any modification. For the same 3D structure, the adhesion force between cells and silicon surface with various structure was weaker while lowering the surface energy. Based on the analysis of fluorescence and scanning electron microscopy images, we proposed an underlining mechanism on how C6 cell morphology and adhesion is controlled by silicon 3D structure and surface energy. In addition, the formation of arbitrary cell patterns was achieved successfully. The findings may provide a conception for the preparation of cell detector and implantable biological scaffold.
This paper demonstrates a novel electro-thermal micro actuator’s design, fabrication and device tests which combine microfluidic technology and microsolidics process. A three-dimensional solenoid microchannel with high aspect ratio is fabricated inside the silica glass by an improved femtosecond laser wet etch (FLWE) technology, and the diameter of the spiral coil is only 200 μm. Molten alloy (Bi/In/Sn/Pb) with high melting point is injected into the three-dimensional solenoid microchannel inside the silica glass , then it solidifys and forms an electro-thermal micro actuator. The device is capable of achieving precise temperature control and quick response, and can also be easily integrated into MEMS, sensors and ‘lab on a chip’ (LOC) platform inside the fused silica substrate.
Microlens arrays with specially required micropatterns are highly desirable for digital optical processors, microimaging systems, optical photolithography as well as various biomedical imaging and detecting applications. However, realization of such devices efficiently remains technically challenging. Here, a facile and efficient route for large-area microlens arrays (MLAs) with programmable micropatterns is demonstrated. The fabrication process involves a femtosecond laser wet etch process combined with the replication process of hot embossing. Special arranged microlens arrays, including a doublet microlens array, a three-microlens group array, a four-microlens group array, and a six-petallike microlens array as examples, were fabricated by this method. The fabricated MLAs exhibit excellent surface morphology quality and optical imaging properties. This presented technique provides an efficient way to flexibly design the size, shape and the arrangement of the MLAs by adjusting the process parameters such as the pulse energy, the number of shots etching time and the distribution of ablation-induced craters and Programming arrangement.
In the last decades, fabrication of microlens array in materials with high-damage threshold has attracted increasing interest, especially in the application of high-power laser. In this paper, we propose an advanced strategy to efficiently fabricate microlens array on the surface of glass using a single-pulsed femtosecond laser wet etch process, which is a combination of high-speed laser scanning and the subsequent chemical etch with HF solution. Based on this method, double-sided microlens array, non-regular arrays consisting of close-packed concave microlens array on one side and regular concave MLA on the other side, were fabricated on the 1cm*1cm glass. Especially over one million microlenses could be acquired within an hour, exhibiting great superiority in practical application. Moreover, the optical properties of the asymmetric double-sided MLA were experimentally characterized, and the experimental results reveal the good light homogenization performance.
This paper reports a flexible fabrication method for 3D solenoid microcoils in silica glass. The method consists of femtosecond laser wet etching (FLWE) and microsolidics process. The 3D microchannel with high aspect ratio is fabricated by an improved FLWE method. In the microsolidics process, an alloy was chosen as the conductive metal. The microwires are achieved by injecting liquid alloy into the microchannel, and allowing the alloy to cool and solidify. The alloy microwires with high melting point can overcome the limitation of working temperature and improve the electrical property. The geometry, the height and diameter of microcoils were flexibly fabricated by the pre-designed laser writing path, the laser power and etching time. The 3D microcoils can provide uniform magnetic field and be widely integrated in many magnetic microsystems.
Femtosecond laser interference is a promising tool for micro-fabrication and micromachining of periodical structures on
the surface of samples or inside transparent materials, but femtosecond laser pulses are very hard to interfere due to their
spectrum widths may reach to several tens of nanometers, and their spectrum widths will be stretched by shorting the
duration according to the Fourier transform. We realized two 25 fs pulses interference and encoded micro-gratings on
Au-Cr thin films using this interference pattern. The interference patterns of two laser pulses with different pulse
durations in sub-hundred femtosecond time domain were calculated to explore the influence of pulse durations on
processing qualities of encoded micro-gratings. The results show that, the shorter pulses are preferable to fabricate
micro-gratings with fine resolution on intractable materials, and longer pulses are helpful to improve encoding efficiency
and contrast ratio of bright & dark interfered fringes. The differences between encoded micro-gratings on Au-Cr thin film
using these interference patterns validated our analysis, which are hardly observed when pulse duration is longer than
100 fs mainly because the size of interfered area is larger than the focal spots. Moreover, the distance between two focal
spots also has been chosen to identify our calculations, and the experimental results are agreement with the calculations.
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