Optimal fabrication of a thin-film thermocouple (TFTC) using Alumel/chromel junctions.

Thin-film thermocouple (TFTC) technology is a novel measurement method that produces a thermocouple sensor during the deposition process, even though it is a complex surface, to obtain the surface temperature. TFTC is a thin film sensor for measuring temperature by contact methods, consisting of two different metals which can generate thermoelectric forces named "Seebeck effects". In the past decade there have been many attempts to measure the cutting temperature during machining processes using TFTF sensors. However, research has not yet progressed to optimize the sensor performance or fabrication process. This paper studies a preliminary technique for the fabrication of a TFTC sensor on a cutting tool surface and optimizes the deposition conditions, TFTC design, and sensor performance. Chromel and Alumel, which are materials commonly used in K-type thermocouples, were used for the thermal evaporation process. When the Chromel has a nickel to chrome ratio of 9:1, low resistivity and minimal variation with increasing temperature were observed. When the contact area of the deposited electrode (+) and (-) poles increased, the resistivity decreased and the TFTC sensitivity improved. Data acquisition tests using a DAQ system connected to the TFTC sensor show the lowest resistivity in TFTC B and C types are able to measure temperature data. It is expected that the heat generated during the cutting process can be detected using the TFTC sensor with B-type shape and Chromel with a 9:1 nickel to chrome ratio.

Measurement of inkjet droplet size based on Fraunhofer diffraction.

Inkjet printers have started to manufacture OLED/QLED pixel arrays for the display industry, and the precise measurement and control of ink droplet volume during the printing process has become important. We investigated the feasibility of Fraunhofer diffraction analysis as a volume measurement tool for fast-moving inkjet droplets. To confirm the basic idea, two Fraunhofer diffraction-based methods were used to calculate the wire diameters of well-known sized and steady-positioned metal wires. The first method was to curve-fit the whole measured diffraction intensity curve with the extensive Fraunhofer diffraction equation. The second one was to use the simple approximate diameter calculation equation with the measured position data of minimum diffraction intensity. The metal wire diameters calculated by the two methods showed less than 1.17% error. For the size measurement of fast-moving inkjet droplets, the first method showed 24.5 µm diameter and 7.7 pL volume, while the second method showed 25.4 µm diameter and 8.58 pL volume. We found that the second method was more suitable for real-time inkjet monitoring because its average computer calculation time was 33 ms, and the first method took an average of 34 ms, about 1000 times more CPU time. Hence, Fraunhofer diffraction analysis as an inkjet droplet volume measurement tool was feasible with a good balance of measurement time and measurement accuracy.

The Effect of Pre-Stretched Substrate on the Electrical Resistance of Printed Ag Nanowires.

One-dimensional nanomaterials have drawn attention as an alternative electrode material for stretchable electronics. In particular, silver nanowires (Ag NWs) have been studied as stretchable electrodes for strain sensors, 3D electronics, and freeform-shaped electronic circuits. In this study, Ag NWs ink was printed on the pre-stretched silicone rubber film up to 40% in length using a drop-on-demand dispenser. After printing, silicone rubber film was released and stretched up to 20% as a cyclic test with 10-time repetition, and the ratios of the resistance of the stretched state to that of the released state (Rstretched/Rreleased) were measured at each cycle. For Ag NWs electrode printed on the pre-stretched silicone rubber at 30%, Rstretched/Rreleased at 10% and 20% strain was 1.05, and 1.57, respectively, which is significantly less than about 7 for Ag NWs at the 10% strain without pre-stretched substrate. In the case of 10% strain on the 30% pre-stretched substrate, the substrate is stretched and the contact points with Ag NWs were not changed much as the silicone rubber film stretched, which meant that Ag NWs may slide between other Ag NWs. Ag NWs electrode on the 40% pre-stretched substrate was stretched, strain was concentrated on the Ag NWs electrode and failure of electrode occurred, because cracks occurred at the surface of silicone rubber film when it was pre-stretched to 40%. We confirmed that printed Ag NWs on the pre-stretched film showed more contact points and less electric resistance compared to printed Ag NWs on the film without pre-stretching.

Effect of Optical and Morphological Control of Single-Structured LEC Device.

We investigated the performance of single-structured light-emitting electrochemical cell (LEC) devices with Ru(bpy)3(PF6)2 polymer composite as an emission layer by controlling thickness and heat treatment. When the thickness was smaller than 120-150 nm, the device performance decreased because of the low optical properties and non-dense surface properties. On the other hand, when the thickness was over than 150 nm, the device had too high surface roughness, resulting in high-efficiency roll-off and poor device stability. With 150 nm thickness, the absorbance increased, and the surface roughness was low and dense, resulting in increased device characteristics and better stability. The heat treatment effect further improved the surface properties, thus improving the device characteristics. In particular, the external quantum efficiency (EQE) reduction rate was shallow at 100 °C, which indicates that the LEC device has stable operating characteristics. The LEC device exhibited a maximum luminance of 3532 cd/m2 and an EQE of 1.14% under 150 nm thickness and 100 °C heat treatment.

Compatibility of endoclips in the gastrointestinal tract with magnetic resonance imaging.

There are no clear guidelines on the compatibility between endoclips that remain in the gastrointestinal (GI) tract and magnetic resonance imaging (MRI). The purpose of this study was to investigate the effect of 3T (T) MRI on endoclips placed in excised pig tissues. Two types of endoclips were assessed: Olympus EZ (HX-610-135L) and QuickClip Pro (HZ-202LR). We assessed tissue damage or perforation and detachment of endoclips under 3T MRI magnetic field. We also evaluated the magnitude of force required to detach the endoclips from the porcine tissue. We measured the magnetic force acting on the Olympus EZ clips. QuickClip Pro clips were used as a control in this study. There was no tissue damage and no detachment of the endoclips (Olympus EZ and QuickClip Pro) during 3T MRI. The force required to detach the Olympus EZ clips ranged from 0.9 to 3.0 N. The translational magnetic force acting on the endoclips was 3.18 × 10-3 N. Ex vivo experiments showed that the magnetic field generated by 3 MRI did not cause tissue damage or perforation and did not detach the endoclips. Olympus EZ clips and QuickClip Pro clips in the GI tract appear to be safe during 3T MRI.

Unexpected Delayed Colon Perforation after the Endoscopic Submucosal Dissection with Snaring of a Laterally Spreading Tumor.

Colonic perforation may occur as a complication of diagnostic and therapeutic colonoscopy. The risk factors for perforation after colorectal endoscopic submucosal dissection (ESD) include an inexperienced endoscopist, a large tumor size, and submucosal fibrosis. The mechanisms of perforation include unintended endoscopic resection/dissection and severe thermal injury. Here, we report a case of colon perforation that occurred after ESD with snaring of a laterally spreading tumor. The perforation was completely unexpected because there were no colorectal ESD-associated risk factors for perforation, deep dissection, or severe coagulation injury in our patient.

Anomalous behaviors of visible luminescence from graphene quantum dots: interplay between size and shape.

For the application of graphene quantum dots (GQDs) to optoelectronic nanodevices, it is of critical importance to understand the mechanisms which result in novel phenomena of their light absorption/emission. Here, we present size-dependent shape/edge-state variations of GQDs and visible photoluminescence (PL) showing anomalous size dependences. With varying the average size (d(a)) of GQDs from 5 to 35 nm, the peak energy of the absorption spectra monotonically decreases, while that of the visible PL spectra unusually shows nonmonotonic behaviors having a minimum at d(a) = ~17 nm. The PL behaviors can be attributed to the novel feature of GQDs, that is, the circular-to-polygonal-shape and corresponding edge-state variations of GQDs at d(a) = ~17 nm as the GQD size increases, as demonstrated by high-resolution transmission electron microscopy.

Size- and doping-dependent time-resolved photoluminescence of doped Si nanocrystals.

Time-resolved photoluminescence (PL) has been studied for B- and Sb-doped Si nanocrystals (NCs) fabricated by ion beam sputtering and annealing. For B-doped Si NCs, the PL intensity as well as the PL lifetime (τPL) increases as NC size (d) varies from 1.5 to 2.6 nm, similar to the case for undoped Si NCs, but with further increase of d, they decrease, possibly resulting from the increase of optically less active NCs with the increase of NCs containing more dopants. The PL intensity and τPL monotonically decrease with increasing doping concentration (nD), irrespective of doping element. Si NCs show smaller τPL in B doping than in Sb doping over the full range of nD. The sharp decrease in PL intensity, accompanied by the gradual decrease in τPL for the higher nD of Sb, may be attributed to Auger recombination due to the presence of Sb inside Si NCs. The higher PL quench rate by Sb compared to B could be attributed to better ionization of Sb dopants in Si NCs.