To address the issues associated with the suturing of skin, products that can seal wounds without suturing are being released globally. This study developed a wound suture patch that incorporates a microneedle that can promote wound recovery. Through strength analyses, a design capable of penetrating the skin without the breakage of the microneedle was selected, and Centella asiatica and PVP were combined to coat the microneedle composed of PEGDA. Penetration experiments using Agarose gels confirmed that the microneedle could deliver the coated drug. The structure for sealing the wound and the final product combined with the tape and microneedle were investigated on artificial skin, where the torn wound was simulated. The results indicated that the tension of the artificial skin was sufficiently tolerated, confirming the binding stability of the structure.

In this study, a polydimethylsiloxane (PDMS) membrane electrolysis micropump activated by a miniaturized wireless power transfer (WPT) system is introduced. The micropump system has total dimensions of 20 × 14 × 8.2 mm3. Combined with a compact WPT system, the micropump enables the delivery of drugs to the treatment area on demand. The WPT system consists of an impedance matching network and a two-stage voltage multiplier. Voltages ranging from 0.8 V to 1.3 V can be generated at different operating distance of 8 cm to 20 cm away from the RF source. The micropump is capable of delivering liquid continuously over a flow ranging from 0.11 µL/min to 4.84 µL/min. This micropump demonstrates a maximum cumulative released drug volume of up to 100.8 µL and was able to produce a pressure that is higher than the intraocular pressure. The results can be used for the study of age-related macular degeneration, diabetic retinopathy, and other ophthalmic diseases.

Recently, as the concentration of fine dust in the atmosphere has increased due to an increase in the use of fossil fuel power plants, automobiles, and factories, it has been increasingly important to measure fine dust in the atmosphere. This is because exposure to fine dust is closely related to the incidence of respiratory and cardiovascular diseases and eventually affects mortality. In this paper, we introduce a MEMS particle sensor based on the resonance frequency shift according to added particle mass. The actuation is driven by Aluminum nitride (AlN), and the total thickness is 2.8 μm. A laser doppler vibrometer (LDV), an optical measuring instrument, was used to measure the resonance frequency of the sensor. Airborne particles naturally were deposited on the sensor. To show the frequency shift according to the particle mass, the frequency shift was measured by dividing the case where the deposited particle mass was small and large. In each case, the frequency shift according to the deposited particle mass was predicted and compared with the frequency shift measured by LDV. It was shown that the deposited particle mass and frequency shift are proportional. The deposition of particulate mass was estimated by image analysis. The frequency shift caused by the particle mass deposited on the sensor was defined as the sensitivity of the sensor. The estimated sensitivity of the sensor is 0.219 to 0.354 kHz/pg.

The circular cross-section of the microchannel plays an important role in recapitulating the physiological relevance of an in-vitro model of blood vessels. In this study, we demonstrate a simple process for turning the single depth of a rectangular microchannel of the mold into a multi-depth circular polydimethylsiloxane (PDMS) microchannel of the replica. The method uses inflated air pressure to deform a partially cured PDMS with simple bench-top equipment. We can produce a wide range of circular microchannels with diameters from 100 mu m to 500 mu m. Based on the self-aligning and bonding principles of partially cured PDMS, this technique can eliminate oxygen plasma bonding and tedious alignment processes. The bonding strength based on the partially cured PDMS can obtain 375 kPa, which is comparable with oxygen plasma bonding. The fabrication parameters, such as the partial curing time of PDMS and the applied pressure, are controlled well to obtain various channel geometries from elliptical to circular cross-sections. We applied the fabrication scheme to reconstruct the geometry of the thrombosis blood vessel in a microfluidic device. Four different geometries of stenosis vessels were successfully produced for investigating the influence of the occlusion shape on thrombus formation. The platelet deposition along the post-stenosis channels was quantitatively observed under time-lapse fluorescence microscopy. Our results indicate that the accumulation of platelets for downstream stenosis is slower and more stable for a concentric stenosis lesion than for an eccentric stenosis lesion. This thrombosis device can be used in real-time clotting analysis models and for antithrombotic drug testing.

In an effort to make microfluidic research more attractive and cost-effective, micromilled polymethyl methacrylate (PMMA) has gained interests as an alternative method to the conventional cleanroom-based micromolds fabrication technologies. The most enabling aspects of micromilling are flexibility on the design changes and the ability to fabricate three-dimensional structures. However, the major drawback of micromilling based micromold fabrication is the presence of burrs and tool marks on the surface after machining. High surface roughness on replicated polymer results in poor bonding strength and optical clarity. The roughness of micromilled surface strongly depends on the machining parameters such as tool size, spindle speed, feed rate, width of cut, and depth of cut. Thus, it is crucial to optimize the machining parameters to obtain a good surface finish. Although the optimal fabrication parameters are used to machine the micromold, the surface roughness of micromilled mold is still relative high compared to the surface of unprocessed PMMA. In this paper, we first optimize the micromilling parameters of Computer Numerical Control (CNC) milling machine to achieve the best possible of surface roughness. We have optimized the machining parameters for a flat endmill with 100 μm, 200 μm, and 400 μm in diameter of spindle speed, feed rate, width of cut, and the depth of cut respectively at 18000 rpm, 20 mm/min, 30 μm, and 20 μm. Then, a method to polish the structured surface of the micromilled mold was developed using the rotary magnetic field. By modifying the CNC program language G-code, we were able to control the polishing path, polishing force and time precisely. Consequently, the burrs and tool marks are completely removed, such that the roughness of the surface is decreased from 350 nm Ra to 30 nm Ra, and 1200 nm Rz to 300 nm Rz while the profile of microstructures is not deteriorated. Finally, we demonstrate our mold fabrication scheme by building a microfluidic immunoassay device with four Quake’s valves and showed the sequential assay process successfully.

The effects of laser energy on the sintering of zirconia (ZrO2) on a magnesium (Mg) alloy were studied. The sintered surface was resistant to corrosion by Na2SO4 solution. The surface micro-nano structure and cross-sectional micro-nano structure of the sintered layer were observed by optical microscopy and scanning electron microscopy (SEM). Incomplete sintering was observed at low volumetric laser energy levels (0.38-0.51 MJ/cm(3)). Defects in the sintered and diffusion layers, and a thinner diffusion layer, were observed at a high volumetric laser energy levels (1.27-1.70 MJ/cm(3)). At an intermediate volumetric laser energy level (0.64-0.76 MJ/cm(3)), the sintered layer quality was high and the ZrO2 sintered layer and diffusion layer were balanced. Elemental analysis of the sintered ZrO2 layer and the diffusion layer was performed using laser-induced breakdown spectroscopy (LIBS). The thickness of the diffusion layer in the sintered region was measured and the diffusion of elemental Zr was analyzed. The diffusion coefficient of ZrO2 (0.94-41.67 mu m(2)/s) was also determined by analyzing the concentration of Zr in the diffusion layer.

In this study, we analyzed the diffusion characteristics of metal composites using laser-induced breakdown spectroscopy (LIBS). We confirmed and quantified the diffusion at the interface between the two metals, which we prepared by soldering followed by heat treatment. The advantage of measuring the spatial distribution of the elements in the specimen using LIBS is that the laser material removal allows us to measure the elements at the interface. We compared the distributions obtained using the LIBS technique to those acquired using other elemental analysis methods, such as energy dispersive spectroscopy (EDS), and analyzed the characteristics of the elemental distributions. We analyzed the metal distributions obtained using the LIBS technique up to nanoscale and compared them to those obtained using the EDS method. In addition, we found defects at the interface, which we also analyzed using LIBS. We investigated the relationship between bonding and diffusion by evaluating the morphologies of fractures in the two metal diffusion layers.

Engineers require scalable processes for patterning nanoscale features on sensitive substrates to enable widespread manufacturability of advanced nanoelectronics. Nanostencils have shown promise, but prior work has relied on electron-beam (e-beam) and focused ion beam (FIB) processes. Nanostencils also frequently exhibit significant edge roughness. Here, we present a fabrication process for nanostencils using double exposure optical lithography and a novel capillary-driven lamination technique to reduce edge blurring, demonstrating sub-diffraction limit features of ~200nm on poly(methyl methacrylate) films. We demonstrate the utility of these stencils by generating metal patterns for use with the 3ω thermal conductivity measurement technique. We find a thermal conductivity of 0.24 Wm-1K-1 and an anisotropy ratio of 9.7. This work demonstrates that nanostencils can be used for scalable, resistfree patterning of nanoscale features on sensitive substrates. INTRODUCTION Traditional photolithography and patterning often requires exposure to caustic chemicals, high temperatures, and/or plasmas, which can damage non-traditional materials for heterogeneous integration applications, such as gate dielectrics [1], organic materials [2] (e.g. BEOL processes [3]), and 2D materials [4]. In particular, organic materials are commonly used in electronics packaging but are often thermally limiting, leading the research community to seek polymers with increased thermal conductivity. The 3ω method, a common thermal characterization technique, is well suited for studying polymers because it can be used on thin films and can distinguish between thermal conduction in multiple directions [5-6]. Although useful, the 3ω method has been difficult to implement with polymers due to the requirement of metal patterning and the incompatibility of many polymers with standard microfabrication techniques. Nanostencils have shown promise as a method of decoupling damaging fabrication processes from sensitive materials by evaporating metals and other materials through nanoscale apertures in contact with the surface [7-8]. Stencils with sub-micron features are generally fabricated using FIB or e-beam lithography, which are slow and costly, so it is valuable to improve manufacturability. Another key issue for nanostencils is that the gap between the substrate and membrane causes edge blurring. Ingle used a magnetic shadow mask and a magnet to pull the mask closer to the substrate to reduce the size of the penumbra [9]. Sidler et al. reported that compliant membranes showed reduced penumbra due to the ability of the membrane to follow the surface topography, including non-ideal roughness [10]. Here, we describe a scalable fabrication platform for nanostencil devices using double exposure optical lithography. We employ a novel capillary-driven lamination technique to bring the membranes into intimate contact with the substrates. We have used these stencils to fabricate platinum features as small as 200 nm on poly(methyl methacrylate) (PMMA) films without e-beam or FIB patterning, offering the first demonstration of manufacturing sub-diffraction limit stencils with double exposure optical lithography. We have also used the stencils to fabricate test structures for 3ω thermal conductivity measurements. Our measurements of a 170nm thin spin-cast PMMA sample show a through-plane thermal conductivity of 0.24 Wm-1K-1, and nearly an order of magnitude anisotropy. The strong anisotropy, favoring inplane thermal conduction, is due to the alignment of polymer chains during viscous shearing while spin coating. Kurabayashi et al. observed this phenomenon in spin-cast polyimide films [11]. This work extends prior work by Kurabayashi et al. by reporting a higher anisotropy ratio in a thinner film. Due to the high anisotropy ratio, heaters nearly an order of magnitude wider than the film thickness demonstrate significant sensitivity to anisotropy.

This paper reports a simple fabrication process for microfluidic channels with circular cross-sectional shapes using a polydimethylsiloxane (PDMS) master and thermal air expansion. This technique can be easily used to generate circular microchannels with a wide range of diameters from 25 to 150μm through a simple bench-top fabrication process. By controlling the gelation time of the PDMS, we can obtain circular microchannels in a variety of diameters. This technique does not require plasma-activated bonding or any alignment processes. We can apply this technique to fabricate networks of circular microchannels to simulate the vascular system, micro-concave platforms for culturing microspheroids, micronozzles for droplet-generation devices, and micro-sized patch clamps for cell immobilization.

While the conventional personal protective equipments (PPEs) covers a variety of devices and garments such as respirators, turnout gear, gloves, blankets and gas masks, several electronic devices such as personal alert safety system (PASS) and heads-up displays in the facepiece have become a part of firefighters personal protective equipments through past several years. Furthermore, more advanced electronic sensors including location traking sensor, thermal imaging caerma, toxic gas detectors, and even physiological monitoring sensors are being integrated into ensemble elements for better protection of firefighters from fire sites. Despite any electronic equipment placed on the firefighter must withstand environmental extremes and continue to properly function under any thermal conditions that firefighters routinely face, there are no specific criteria for these electronics to define functionability of these devices under given thermal conditions. Although manufacturers provide the specifications and performance guidelines for their products, their operation guidelines hardly match the real thermal conditions. Present study overviews firefighter's fatalities and thermal conditions that firefighters and their equipments face. Lastly, thermal packaging methods that we have developed and tested are introduced.

This paper reports, for the first time, a single-chip ovenization of a fully-encapsulated MEMS gyroscope to improve the stability of the scale factor and bias. We use the frequency output of the gyroscope as a thermometer, and, in turn heat the device through an on-chip silicon heater defined in the encapsulation layer. During temperature-controlled operation, the scale factor holds constant and the bias remains less than 1°/s, even as external temperature changed from 0-80°C.

매년마다 신장질환으로 고통 받는 사람들이 증가하는 추세이다. 가장 흔한 치료법 중 하나는 혈액 투석인데, 이 방법은 많은 시간이 걸리고, 비용이 많이 드는 방법이다. 이러한 이유 때문에, 인공신장연구의 중요성이 대두되고 있다. 혈액에서 크레아티닌을 여과하는 것은 신장의 주요 기능 중 하나이다. 우리는 이 기능에 초점을 맞춘 새로운 2 채널 마이크로 플루이딕 칩을 고안하였다. 두 개의 PDMS 층을 결합하기 위하여, 아크릴을 가공한 하우징 시스템이 개발하였으며, 이 방법은 여과막을 쉽게 바꿀 수 있다는 이점이 있다. 우리는 알루미늄 양극 산화물(AAO)을 여과막으로 사용하였다. 여과된 용액은 자페반응(Jaffe reation)을 이용하여, 크레아티닌 농도별 흡광도 차이를 분석하였다. 크레아티닌의 양에 대한 표준식을 만들어, 측정한 데이터를 보간하여 여과된 용액의 농도를 확인하였다. 실험을 통하여 유량 및 크레아티닌 농도에 따른 여과율을 얻을 수 있었다.

In order to evaluate the degradation rate of porous Si in artificial cerebrospinal fluid and obtain more accurate results, the effect of solution aging time on the stability of the ammonium molybdate colorimetric assay was investigated. Following the protocol of the colorimetric assay, the blue colored solutions with various silicic acid concentrations were prepared and then aged for different time periods up to 7 h. On the basis of linear regression analyses, the absorbance value of the blue colored solution was directly proportional to the silicic acid concentration. Moreover, the optimal aging time span of the solution maintained until 7 h, depending on the stability of the solution.

반도체센서의 응력에 따른 전기적 특성을 프로브 스테이션 위에서 측정하기 위해 소형 4점 굽힘 장치를 개발하였다. 4점 굽힘 장치는 $60{\times}83mm^2$의 면적을 갖는 소형 장치로 마이크로미터를 통해 정확한 변위를 인가함으로서 가해진 응력을 구할 수 있다. 유한요소해석법을 사용하여 기기의 오차를 예측하고 정밀도를 향상하였다. 실험적으로는 4점 굽힘 장치로 인가된 응력을 검증하기 위해 스트레인 게이지로 검증하였다. A four point bending apparatus has been developed to measure semiconductor sensor piezoresistance inside a four inch probe station. The apparatus has a footprint of $60{\times}83mm^2$ and can apply $10{\mu}m$ displacements using a vertical micrometer stage. We used finite element analysis to predict and improve the accuracy of the instrument. Finally strain gauge attached on a silicon test piece was used to experimentally verify the setup.

SiO2 and Si3N4 layers to be used in the microfabrication of a neural probe were formed on Si substrate through plasma enhanced chemical vapor deposition (PECVD). To ensure their cytoconnpatibility, the surface properties and cytocompatibility of the PECVD-formed SiO2 and Si3N4 were investigated and compared. SEM images showed the SiO2 and Si3N4 layers consisted of nano-sized particles. In accordance with water contact angle measurement, the surface of both PECVD-formed SiO2 and Si3N4 layers were hydrophilic and there was no significant difference in wettability between them. A breast cancer cell line (MCF-7) was seeded on their surface to evaluate the cytocompatibility. After 3 days of cell culture, the adherent cells on PECVD-formed Si3N4 surface did not spread as well as those on Si or PECVD-formed SiO2, and the cells on the surface of PECVD-formed SiO2 and Si3N4 were significantly less than on Si. At day 7, however, there was no significant difference between them, in terms of cell morphology and number. Therefore, the PECVD-formed SiO2 and Si3N4 layers did not exhibit acute cytotoxicity and were as cytocompatible as tissue culture polystyrene.

외팔보의 형상적인 해석과 압전효과에 의거하여, 최대 전력량 산출을 위한 에너지 수확기를 설계하였다. 두가지의 외팔보 형상으로 에너지 수확기의 구조가 설계되었다. 에너지 수확기의 성능을 좌우하는 주요 변수는 외팔보 형상과 끝단에 부착된 질량이다. 수확되는 전하량은 압전재료의 압전상수와 외팔보의 기계적인 변형량에 비례한다. Based on the structural analysis of cantilever and the piezoelectric effect, we propose a new design of piezoelectric cantilever to harvest maximum vibration energy. Geometric parameters of piezoelectric cantilever are optimized according to two different types of cantilever structure. The main factors that affect the harvesting performance of the cantilever was the shape of the cantilever and the load at the free end. The amount of charge is affected by piezoelectric constant and mechanical strain of the cantilever.

MEMS devices are particularly promising as neuronal recording tools due to their small dimensions, suitability for multielectrode recording, integration with on-chip electronics, and potential for implantability. This chapter gives a recent overview of the state of the art in neural MEMS. Starting with a brief background on neuronal communication, the chapter reviews the development and latest advances in the well-known Michigan and the UTAH probes. The neural probe design from the EU-funded project is contrasted with these established Si-based probes for extracellular recording. The chapter touches on drug delivery and optical stimulation mechanisms that have been built into MEMS-based neural probes. It addresses the need for and issues of flexible neural probes that attempt to reduce the mechanical mismatch at the probe tissue interface, leading to a lower degree of host response and inflammation. Several different fabrication approaches for neural probes from single-sided assembly to flexible probes to growth of neural probes using vapor-liquid-solid mechanism have been discussed. Neural recording with MEMS devices are largely for extracellular neuronal recording. The chapter looks at intracellular neuronal recording with MEMS and the challenges in micromachining these devices. The chapter ends by discussing the biological response of tissue to implanted probes and the integrated circuit (IC) challenges for wireless recording with implantable devices.