Fabrication of large-area cylindrical microlens array based on electric-field-driven jet printing

Hot embossing has been widely used in fabricating microlens arrays because of its low cost, high efficiency, and high quality. The process parameters such as molding temperature, molding pressure, and holding temperature affect the microlens array’s replication quality. This work selected the stainless steel S136H tool steel as the mold material to process an aspheric microlens array structure through ultra-precision milling. Polymethyl methacrylate (PMMA) microlens arrays with different surface replication were prepared by controlling the molding temperature, molding pressure, and holding temperature. By analyzing the surface quality, contour replication, and optical imaging of hot-embossed samples, the optimal molding temperature of PMMA for optimal replication of aspheric lens arrays was determined as 130 °C. Besides, the internal elastic recovery of PMMA affected the dimensional accuracy and optical performance of the lens. The results showed that, at the molding pressure of 400 N and the holding temperature of 60 °C, the surface defects were eliminated, and the aspheric lens array had perfect replication with a profile deviation of only 4 μm. The aspheric microlens array with good quality was eventually achieved by these optimal process parameters, which provides a foundation for producing aspheric microlens arrays in a low-cost and high-efficiency way.

We demonstrate an efficient method for fabricating high-quality cylindrical microlens arrays (CMLAs) on the surface of fused silica, fully based on spatially shaping of a femtosecond laser beam from Gaussian to Bessel distribution. As the envelope of shaped spatial intensity distribution matches the profile of cylindrical microlens perfectly, a CMLA with more than 50 uniform microlenses is fabricated by simple line scanning. The radius and height of these microlens units can be finely controlled by adjusting the power of laser pulses. Excellent optical imaging and high-speed fabrication performances are also demonstrated by our fabricated CLMA.

Microfluidic paper-based sensors as a new type of microsample detection technology are widely used in medical diagnosis, environmental monitoring, and food safety testing. Inkjet printing has the advantages of simplicity, speed, flexibility, high resolution, low cost, and efficient mass production and has become one of the most cutting-edge technologies in the manufacture of paper-based sensors. In this work, a fully inkjet printing preparation method was proposed for paper-based sensors, which can achieve high-precision, multichannel, and visual fluorescence detection. Three kinds of fluorescent carbon dots (CDs; r-CDs, b-CDs, and y-CDs) were fabricated into inkjet ink by adding a suitable ratio of solvent, PEG, and surfactant FS3100 to control its viscosity, surface tension, and other influencing factors, obtaining the best-visualized fluorescence response on paper. To optimize the full inkjet printing process of the paper-based sensor, we studied the influence of factors such as the hydrophobic material AKD formula, postprocessing conditions, and the structure of the hydrophilic and hydrophobic channels on the paper-based detection accuracy, and it was found that proper AKD concentration, curing time, and temperature can make AKD fully react with paper-based surface groups and produce more hydrophobic groups on the surface and inside of the filter paper, which can form paper-based microfluidic sensors with clear boundaries and fast transmission speed at low cost and high efficiency. The fabricated sensor is used for the fluorometric determination of vitamin C (AA), NO2-, and sunset yellow (SY) at the same time, and the limits of visual detection by eyes are 6 mmol/L (NO2-), 60 μmol/L (SY), and 40 mmol/L (AA). The mechanism of inkjet printing is investigated in detail, which is simple, reliable, and easy to realize mass production and can realize highly sensitive, on-site, and visual detection for food additives.

Double‐vacuum‐bag (DVB) process, as an effective out‐of‐autoclave (OoA) technology, can manufacture composite materials with low void content and high mechanical properties. Therefore, this paper aimed to achieve low void content, the effects of pressure difference between inner and outer bags, dwelling temperature, and dwelling time on the void of composite laminates were studied based on orthogonal experimental method. The void content and morphology of laminates were statistically analyzed, by observing the microscopic images of the samples on cross‐section. The results show that the pressure difference between the inner and outer bags has a significant impact on the void content and morphology, while the dwelling temperature and dwelling time have little effect. In addition, with the variance analysis and extreme difference analysis, the optimal process parameters were determined as follows: pressure difference between inner and outer bags was 0 MPa, dwelling temperature was 110°C, and dwelling time was 15 min. The void content of composite laminates manufactured under these parameters is 0.07%, less than 1% requirement for aerospace components, and interlaminar shear strength (ILSS) is 110 MPa, which is 54.93% higher than the single‐vacuum‐bag (SVB) process. Generally, the void content and ILSS reached the level of hot press process with 0.6 MPa. Highlights Influence of different DVB process parameters on void were studied. Void content manufactured with the optimal DVB process parameters was less than 1%. ILSS of laminate with the optimal DVB process parameters was equal as hot press process.

We characterized the optical properties of a photoresist-based micro-lens using a stressed liquid crystal matrix for high-speed variation of the focal distance. We also determined the operational parameters for the adaptive optical spherical and cylindrical micro-lens arrays. The resulting optical elements feature fast response times, around 1 ms, with a focal length range of 2600-970 μm.

Gradient index micro lenses for laser diode applicationsR. Goering, T. Possner, B. MesserschmidtFraunhofer Institution for Applied Optics and Precision EngineeringSchillerstrasse 1 , 07745 Jena, GermanyABSTRACTCollimating and diverging cylindrical micro lenses with N.A. up to 0.60 fabricated by thermal silver ion exchangein a special designed glass type are reported. Cylindrical microlens arrays are fabricated by field assistet ion-exchange. Applications to fiber coupling as well as to diode bar collimation are discussed.Keywords: ion-exchange, GRIN-components, laser diode beam shaping, laser bar collimation, fiber coupling1. INTRODUCTIONMicrooptical GRIN-lenses with high N.A. are very useful for the transformation of the strongly divergent andasymmetric beam emitted from semiconductor laser diodes and laser diode bars to a well-collimated beam orto a focused spot. Preferred applications are the coupling between laser diodes and optical fibres, the pumpingof solid state lasers as well as optical scanning. High N.A., a nearly diffraction limited pertormance and lensdimensions of a few hundred microns are required. In a previous paper we presented the formation of one-dimensional cylindrical microlenses by a two step silver ion-exchange process1. Here we would like to discussthe optimization of these components and a number of new elements fabricated by similar ion-exchangeprocesses and applications which could not be realized by standard SELFOC-lenses.Figures 1 and 2 show flat GRIN-components and ion-exchange techniques for their realization. The formationof diverging lenses is possible in a single ion-exchange step. For the generation of cylindrical collimating lenseswe use a two step process, proposed by Ohmi2. Cylindrical microlens-arrays are produced by a field-assistedexchange using a masked substrate.Fig. 1: Thermal ion-exchanged GRIN components

We developed the technology of microslice integral field units some years ago as the next step in SAURON type microlens IFU design with typically 5 times more spatial elements (spaxels) for the same spectrograph and spectral length aiming at 1,000,000 spaxels IFUs. A full instrument for laboratory demonstration composed of the fore-optics, the IFU, the spectrograph and the detector has now been built and tested. It has about 10,000 spatial elements and spectra 150 pixel long. Our IFU has 5 cylindrical microlens arrays along the optical axis as opposed to one hexagonal array in the previous design. Instead of imaging pupils on the spectrograph input focal plane, our IFU images short slitlets 17 pixel long that keep the spatial information along the spatial direction then giving 17 spaxels per slitlet instead of one in pupil imaging. This removes most of the lost space between spectra leaving place for more and keeps the spatial information over the element size while pupil images lose it. The fore-optics re-images the field on the input of the IFU. They are made of cylindrical optics to get the desired different magnifications in both directions. All the optics and detector fit in a cylinder 35 mm in diameter and 280 mm long. With a different set of fore-optics on a 4-m telescope, a field of 43 x 6.7 with spatial elements of 0.14 x 0.22 could be observed so 12 of these mini-spectrographs would cover a field surface area of about 1 arcmin 2 and 120,000 spaxels.

In order to optimize the preparation process of microlens arrays, improve preparation efficiency, and reduce preparation costs, 248 nm KrF excimer laser direct writing is combined with a motion mask to prepare microlens arrays on PMMA substrates. Firstly, a specific exposure mask based on the contour characteristics of the microlens unit was designed, and the preparation principle was analyzed. Using COMSOL Multiphysics 6.3 simulation software, a microlens preparation model was built to intuitively describe the process of preparing microlenses by the motion mask method. Secondly, a preparation system was built, and the laser processing technology was optimized. Finally, microlens arrays were prepared based on the optimized process, and an optical microscope and white-light interferometer were used to observe their morphology. The experimental results show that this method can effectively prepare cylindrical and circular microlens arrays. The width of the cylindrical microlens array unit exceeded 90 μm, the height was 7.08 μm, and the roughness was 0.09 μm. The diameter of the circular microlens array unit was φ100 μm, the height was 4 μm, and the curvature radius was 230 μm. The geometric dimensions of the mask can be adjusted to obtain microlens units of the desired size, achieving personalized preparation of microlens arrays. The excimer laser motion mask method can prepare various types of microlens arrays, and the array units have a high consistency and high surface quality, which helps to improve the efficiency, flexibility, stability, and specificity of microlens array preparation.

Highly efficient and stable perovskite solar cell with sodium glycinate additive

Tannic acid (TA)-based coating modified membrane enhanced by successive inkjet printing of Fe3+ and sodium periodate (SP) for efficient oil-water separation

In rotary friction welding experiments of wood, the influence of different process parameters on the welding temperature was investigated, followed by an analysis of how temperature affects the content of lignin, hemicellulose, and other components in the welded zone. Mass spectrometry was conducted under the optimal process parameters to accurately analyze the chemical composition within the welding zone. This study conducted rotary friction welding experiments using thermally modified Scots pine (a physically modified wood material treated at high temperatures to improve its properties) and untreated Scots pine. Experimental groups were designed based on tenon-to-hole diameter ratio, rotational speed, and feed rate. A series of single-factor experiments was carried out to investigate how each process parameter affects the temperature variation in both untreated and thermally modified wood. The results showed that the tenon-to-hole diameter ratio primarily influenced the peak temperature at the welding interface, while the feed rate mainly affected the rate at which this peak temperature was reached. In contrast, the rotational speed had a relatively minor effect on the welding interface temperature. Furthermore, mass spectrometry analysis under optimal welding conditions revealed the generation of various compounds, predominantly furfural, pinene, camphene, and borneol, in differing concentrations. Notably, differences were observed in the welded interfaces between treated and untreated Scots pine. Compared to the untreated wood, the welded zones of the thermally modified material were denser and more robust.

Inkjet printers are the most commonly owned printers because of their low cost, high printing quality, and ease of use. The four major inkjet printer manufacturers are Canon, Epson, Hewlett-Packard, and Lexmark. The inkjet printer business has adopted the “bait and hook” business strategy, offering the basic printer product at a low (possibly below cost) price while charging a higher price for their proprietary ink cartridges. Table 1 shows the pricing of different ink jet printers and ink cartridges from the four major manufacturers. With technology advancement, inkjet printers have improved in quality and reduced in price. As seen in Table 1, the printer (being more technologically complex to make than the ink cartridge) is relatively inexpensive. This is a business tactic used to attract more people to buy the printer. The manufacturers are trying to improve their overall profit margin by charging higher prices than they would have normally done for their proprietary ink cartridges. The setting of printer and cartridge prices must therefore be closely linked and studied, as they affect the overall profitability and survival of the printer company. According to LYRA research (http://www.lyra. com/), the total revenue from inkjet printers and ink cartridges exceeded $45 billion in 2006. I.T. Strategies (http://www.it-strategies.com/) expects the inkjet printer market to grow to $58 billion by 2009. It expects the largest segment of the revenue to come from ink cartridges, with the revenue rising from $20 billion in 2004 to $33 billion in 2009. The printer business is very lucrative, and it is crucial for the survival of a company that produces printers to use a “good and flexible” business decision tool to price the printer and ink cartridges. Allan Table 1 Sample Inkjet Printer and Cartridge Prices

Fabrication of solar cells has attracted more and more attention in recent years due to the high demand of energy of modem society. However, one of the major challenges of solar cell manufacturing is associated with the high cost. The development of new materials and fabrication techniques are highly demanded. Various printing techniques, such as spin coating, screen printing, doctor blading, pad printing and inkjet printing, have been adopted in the fabrication of solar cells. In view of their uniqueness and advantages such as noncontact process, high material utilization rate, low cost, flexible and digital patterning, the inkjet printing is believed to be the next generation solar cell manufacturing technology. In this paper, the applications of inkjet printing in both inorganic solar cell and organic solar cell are reviewed, from lab scale to industry production. The related challenges on the technical issues and optimization of the process in the applications are also addressed.

The HyS process, driven by solar power, has great potential to reach high-efficiency and low-cost hydrogen production without greenhouse gas emissions. The high-temperature section of the HyS cycle, which operates the catalytic decomposition of sulfuric acid into sulfur dioxide, oxygen, and water, is a fundamental part of the cycle affecting the overall plant efficiency and cost. Therefore, a high-performance catalyst (i.e., low cost, high catalytic activity, and low degradation catalyst) is of critical importance to achieve high efficiency and low hydrogen cost. Research and development has highlighted that a Pt-based monometallic catalyst had unacceptable catalytic activity and performance degradation for a high-efficiency and low-cost hydrogen production process. A high-efficiency solar receiver-reactor system, which incorporates the new catalyst, also needs to be developed to achieve the required plant efficiency and cost. Greenway Energy (GWE) and the University of South Carolina (USC), partnering with HydroGEN node laboratories Idaho National Laboratory (INL), Savannah River National Laboratory (SRNL), and National Renewable Energy Laboratory (NREL), propose the development of a new catalyst formulation, included in a novel solar receiver-reactor concept, to be tested experimentally in the last part of the project.

CRISPR/Cas9 Genome-Editing System in Human Stem Cells: Current Status and Future Prospects