Durable Soft Mold for Imprinting of High-Adhesive Resin

A variety of polymer resins have been used to fabricate micro/nano structures via imprint lithography. In addition, with an interest in productivity, there is an increasing demand for the study of the process of easily demolding a cured resin from a mold for continuous fabrication of micro/nanostructures applying imprint lithography to the roll-type equipment. Among these polymer resins, Norland optical adhesive (NOA) in particular is widely used to fabricate micro/nano structure-based functional surfaces because of its shape memory characteristics, biocompatibility, and great optical characteristics. However, the cured NOA is originally used as an epoxy-based adhesive with its high adhesion. NOA has many advantages as a UV-curable adhesive, but as a resin in the imprint process, such adhesion brings a limitation. This high adhesion of cured NOA causes defects in the mold during the demolding process, so it is difficult to apply it to the continuous fabrication process. Here, we present a durable polyurethane acrylate (PUA) soft mold capable of clean demolding of an epoxy-based polymer resin having high adhesion by depositing metal on a surface. Au and Ni were deposited to a thickness of 100 Å by using an E-beam evaporator. To verify the surface characteristics, each metal-deposited soft mold was compared with the previously used soft mold by measuring the contact angle and calculating surface energy. To test a performance of our soft mold, we imprinted nanoline pattern with NOA as a resin using metal-deposited soft mold in roll to roll (R2R) process for more than 240 replications for 90 min of operation time. It is expected that this study can be used for mass production of pattern with epoxy-based patterns required in many fields

Students' Satisfaction and Performance in Flipped Physics Classrooms Having Different Proportions of Face-to-face Lecturing

Flipped learning is an instructional design implementing peer instruction by reducing traditional face-to-face lecturing. However, students tend to be afraid of replacing face-to-face lecturing with peer instruction. We applied the flipped learning method to two sections of General Physics 2 for electromagnetism and modern physics. We controlled the ratio of face-to-face lectures to the entire class meeting hours to be 1/2 for one section (N=288) and 1/3 for the other section (N=296). Students' achievements were not statistically distinguished between the two sections. Students' satisfaction with lecturing was indistinguishable. However, while students in the 1/3 section prefered peer instruction, those in the 1/2 section were satisfied with instructional design. According to a correlation analysis, students' satisfaction correlated with achievements only in the 1/2 section. Therefore, we conclude that flipped learning is systematically worked in the 1/2 section rather than in the 1/3 section

Physiological and Behavioral Effects of SiO2 Nanoparticle Ingestion on Daphnia magna

The increasingly widespread use of engineered nanoparticles in medical, industrial, and food applications has raised concerns regarding their potential toxicity to humans and the environment. Silicon dioxide nanoparticles (SiO2 NPs), which have relatively low direct toxicity, have been increasingly applied in both consumer products and biomedical applications, leading to significantly higher exposure for humans and the environment. We carried out a toxicity assessment of SiO2 NPs using the common water flea D. magna by focusing on physiological and behavioral indicators such as heart rate, swimming performance, and growth. Exposure to SiO2 NPs did not produce acute or chronic toxicity at limited concentrations (<100 μg/mL), but did have statistically significant negative effects on heart rate, swimming distance, and body size. The use of fluorescein isothiocyanate in a silica matrix allowed the tracing and visualization of clear SiO2 NP accumulation in D. magna, which was confirmed by ICP-MS. Although exposure to SiO2 NPs seemed to affect cardiac and swimming performance, such end-point experiments may be insufficient to fully understand the toxicity of these nanoparticles. However, the physiological and behavioral changes shown here suggest potential adverse effects on the aquatic environment by substances previously considered nontoxic

Scalable Fabrication of Flexible Microstencils by Using Sequentially Induced Dewetting Phenomenon

We present the physics of sequential dewetting phenomenon and continuous fabrication of a polymeric microstencil using dewetting phenomenon with roll-to-roll imprinting equipment. To realize dewetting-assisted residual-free imprinting, mold material, polymer resin, and substrate were selected via interfacial surface energy analysis. In addition, optimal parameters of the continuous process were also studied by experimentally comparing the resultant shape of the microstencil depending on the process speed, aspect ratio of the mold, and applied pressure. As a result, the polymeric microstencil was produced continuously in very high yields, and its maximum resolution reached 20 μm in diameter. For an easy, continuous demolding during the roll-to-roll process, the material chosen for the substrate film was paraffin-coated film, which has the surface energy low enough for dewetting while having a higher adhesion value than polydimethylsiloxane mold. This versatile, high-throughput microstencil fabrication process can be used in many applications requiring flexibility, scalability, and specific material, and high productivity

High-Performance Organic Semiconductors for Thin-Film Transistors Based on 2,7-Divinyl[1]benzothieno[3,2-b]benzothiophene

We have synthesized two novel organic semiconductors, which have a symmetrically substituted 2,7-divinyl[1]benzothieno[3,2-b]benzothiophene backbone. They show good electrical performances on a SiO2/Si substrate, with high field-effect mobilities of up to 0.4 cm2 V-1 s-1, and can easily be synthesized in large quantities. In addition, there is no significant change in the mobility of DPV-BTBT even after the device is exposed to air for at least 60 days (further monitoring is in progress), showing that it is a promising air-stable p-channel organic semiconductor that can be applied to all-organic flexible electronic devices

High-throughput in vivo genotoxicity testing: an automated readout system for the somatic mutation and recombination test (SMART).

Genotoxicity testing is an important component of toxicity assessment. As illustrated by the European registration, evaluation, authorization, and restriction of chemicals (REACH) directive, it concerns all the chemicals used in industry. The commonly used in vivo mammalian tests appear to be ill adapted to tackle the large compound sets involved, due to throughput, cost, and ethical issues. The somatic mutation and recombination test (SMART) represents a more scalable alternative, since it uses Drosophila, which develops faster and requires less infrastructure. Despite these advantages, the manual scoring of the hairs on Drosophila wings required for the SMART limits its usage. To overcome this limitation, we have developed an automated SMART readout. It consists of automated imaging, followed by an image analysis pipeline that measures individual wing genotoxicity scores. Finally, we have developed a wing score-based dose-dependency approach that can provide genotoxicity profiles. We have validated our method using 6 compounds, obtaining profiles almost identical to those obtained from manual measures, even for low-genotoxicity compounds such as urethane. The automated SMART, with its faster and more reliable readout, fulfills the need for a high-throughput in vivo test. The flexible imaging strategy we describe and the analysis tools we provide should facilitate the optimization and dissemination of our methods

Automated SMART process.

<p>The methods used to automate the SMART are depicted with a flow diagram. The general flow of the method is described in (A). Each step in the process is depicted by a rectangle, with data inputs and outputs depicted using elliptical shapes. (B) Steps in automated acquisition. (C) Steps in focus stack analysis and the extraction of data on <i>mwh</i> hairs, cells, and spots. Discard error (1–3) refers to detection of (1) abnormal hair shape, (2) abnormal hair orientation, and/or (3) abnormal position relative to the wing surface. (D) Steps in the construction of the genotoxicity wing score dose-response curve and the characterization of compound genotoxicity.</p

SMART automated image and data acquisition.

<p>To test chemical-induced genotoxicity, fly larvae (A) were exposed to increasing doses (B; c0, ci, for instance) of a test compound and their wings (C), along with those of other flies from their treatment group, were collected on a slide. A single wing is shown in the red rectangle. (D) Wing position and orientation (orange arrow) were detected automatically, and acquisition regions were defined (green rectangles, each corresponding to a microscope field of view). All acquisition positions defined were compiled in a single file used by the microscope to perform multipoint acquisitions. (E) At each point, a focus stack showing wing hairs and their spatial organization was acquired. (F) A close-up of a focus stack maxima projection along the focus axis, showing hair organization. Hairs from the upper and lower sides of the wing overlap in this view. (G) For illustrative purposes, lower wing hairs have been separated by manually selecting a set of z-slices before projection. Focusing on a single wing side, one can distinguish the regular position and orientation of the hairs. Hairs with an <i>mwh</i> phenotype are visible (white dashed circle).</p