Injection Compression Molding of Replica Molds for Nanoimprint Lithography

Abstract: As a breakthrough in the cost and durability of molds for nanoimprint lithography (NIL), replica molds are fabricated by injection compression molding (ICM). ICM is commonly used for optical disks such as DVDs or Blu-ray disks and is also a practical fabrication method for nanostructures. In this paper, I successfully demonstrated the fabrication of cycloolefin polymer replica molds with structures smaller than 60 nm by ICM. Furthermore, ultraviolet (UV)-NIL using these replica molds was demonstrated. UV-cured resist was replicated over an area of 60 mm diameter. The degree of replication by UV-NIL in the first usage of each replica mold had good repeatability. Because ICM is a high-throughput, low-cost process, the replica mold can be disposed of after a certain time for UV-NIL. This method leads to a high-integrity UV-NIL process of patterned media because multiple large-area replica molds can be fabricated simultaneously

Laser-Assisted Thermal Imprinting of Microlens Arrays—Effects of Pressing Pressure and Pattern Size

Polymer films with nano- or microstructured surfaces have been widely applied to optical devices, bioplates, and printed electronics. Laser-assisted thermal imprinting (LATI), in which a laser directly heats the surfaces of a mold and a thermoplastic polymer, is one of the high-throughput methods of replicating nano- or microstructures on polymer films. Only the surfaces of the mold and polymer film are heated and cooled rapidly, therefore it is possible to replicate nano- or microstructures on polymer films more rapidly than by using conventional thermal nanoimprinting. In this study, microlens arrays (MLAs) were replicated on polymethylmethacrylate (PMMA) films using LATI, and the effects of the pressing pressure (10−50 MPa) and the pattern size (33- and 5-μm pitch) of the MLA on the filling ratio were investigated by analyzing a microlens replicated using different laser-irradiation times (0.1−2 ms). The filling ratio increased with increasing pressing pressure and laser-irradiation time in the replication of MLAs with varying sizes, while the flow of the PMMA varied with the pressing pressure and laser-irradiation time. It was found that during filling, the shape of the polymer cross-sectional surface demonstrated a double and single peak in the 33- and 5-μm-pitch patterns, respectively. This was because the depth of the heated area in the 33-μm-pitch pattern was smaller than the pattern size, whereas that of the 5-μm-pitch pattern was comparable to (or larger) than the pattern size

Impact of the tumor microenvironment in predicting postoperative hepatic recurrence of pancreatic neuroendocrine tumors

The disease frequency of pancreatic neuroendocrine tumors (PNETs) has been growing, and postoperative hepatic recurrence (PHR) is one of the factors affecting patient prognosis. The present study aimed to investigate biomarkers of PNETs in the primary disease site to predict PHR using immunohistochemical analysis for tumor-infiltrating lymphocytes (TILs: CD3, CD8 and CD45RO), human leukocyte antigen (HLA) class I, alpha-thalassemia/mental retardation X-linked (ATRX), death domain-associated protein (DAXX), mammalian target of rapamycin (mTOR) and phospho-mTOR (p-mTOR). Correlations were analyzed between TILs and the biomarkers, clinicopathological features and prognosis. Sixteen patients with PNETs who underwent radical surgery at our hospital were reviewed. We analyzed the correlation between PHR and immunohistochemical characteristics, and also between disease-free survival (DFS) or overall survival (OS) and the immunohistochemical characteristics. We found that PHR was associated with the expression patterns of DAXX and p-mTOR. No association was found between PHR and patient background, TILs or other biomarkers. DFS was found to be associated with ATRX, DAXX and p-mTOR. OS was associated only with p-mTOR. In conclusion, ATRX, DAXX and p-mTOR are useful molecular biomarkers for predicting PHR in patients who undergo radical surgery for PNETs. Use of these biomarkers will enable earlier decisions on which patients may benefit from adjuvant therapy

Stretchable Kirigami Components for Composite Meso-Scale Robots

Layer-by-layer manufacturing of composite mechanisms allows fast and cost-effective fabrication of customized robots in millimeter and centimeter scales which is promising for research fields that rely on frequent and numerous physical iterations. Due to the limited number of components that can be directly integrated in composite structures, however, often an assembly step is necessary which diminishes the benefits of this manufacturing method. Inspired by the Japanese craft of cutting (kiri-) paper (-gami), Kirigami, we introduce quasi-2D and highly stretchable functional Kirigami layers for direct integration into the composite mechanisms. Depending on the material and geometrical design; functional Kirigami layers can perform as flat springs, stretchable electronics, sensors or actuators. These components will facilitate the design and manufacturing of composite robots for different applications. To illustrate the effectiveness of these components, we designed and realized a foldable composite inchworm robot with three Kirigami layers serving as actuator, sensor and contact pad with directional friction. We elaborate on the working principle of each layer and report on their combined performance in the robot

Investigation of Insertion Phenomena with Needles Treated by Plasma Etching

AbstractPain during injection of a medical needle is greatly influenced by the surface roughness and geometry of its cutting edges. An ion- plasma sputtering treatment is a promising candidate as a clean and precise polishing method for the painless needles. In this paper, the mechanism of the reduction of inserting force of the plasma-treated needles is investigated by microscopically observing artificial skins and needles during insertion. It was found that the time distribution of insertion force was influenced by the roughness at the cutting edges. Plasma-treated needles resulted in force reduction by approximate half in comparison of untreated ones. Furthermore, the microscopic observation found that the sharp dropping of force was occurring at the corners between cutting faces. Using the plasma-treated needle, the sharp dropping was significantly decreased. The plasma-etching treatment will lead to a clean finishing process for painless medical needles