Wet anisotropic etching is extensively employed in silicon bulk micromachining to fabricate microstructures for various applications in the field of microelectromechanical systems (MEMS). In ...addition, it is most widely used for surface texturing to minimize the reflectance of light to improve the efficiency of crystalline silicon solar cells. In wet bulk micromachining, the etch rate is a major factor that affects the throughput. Slower etch rate increases the fabrication time and therefore is of great concern in MEMS industry where wet anisotropic etching is employed to perform the silicon bulk micromachining, especially to fabricate deep cavities and freestanding microstructures by removal of underneath material through undercutting process. Several methods have been proposed to increase the etch rate of silicon in wet anisotropic etchants either by physical means (e.g. agitation, microwave irradiation) or chemically by incorporation of additives. The ultrasonic agitation during etching and microwave irradiation on the etchants increase the etch rate. However, ultrasonic method may rupture the fragile structures and microwave irradiation causes irradiation damage to the structures. Another method is to increase the etching temperature towards the boiling point of the etchant. The etching characteristics of pure potassium hydroxide solution (KOH) is studied near the boiling point of KOH, while surfactant added tetramethylammonium hydroxide (TMAH) is investigated at higher temperature to increase the etch rate. Both these studies have shown a potential way of increasing the etch rate by elevating the temperature of the etchants to its boiling point, which is a function of concentration of etch solution. The effect of various kinds of additives on the etch rate of silicon is investigated in TMAH and KOH. In this paper, the additives which improve the etch rate have been discussed. Recently the effect of hydroxylamine (NH
2
OH) on the etching characteristics of TMAH and KOH is investigated in detail. The concentration of NH
2
OH in TMAH/KOH is varied to optimize the etchant composition to obtain improved etching characteristics especially the etch rate and undercutting which are important parameters for increasing throughput. In this article, different methods explored to improve the etch rate of silicon have been discussed so that the researchers/scientists/engineers can get the details of these methods in a single reference.
This title was first published in 1980: This volume analyzes Japan's industrial organization both from a historical perspective and by looking in details at specific industries such as iron, steel ...and the automotive industry. Big business, business groups and industrial policy are also discussed. The volume also provides a survey of the literature in Japanese which will help the reader in search of original sources.
Monitoring exhaled breath is a very attractive, noninvasive screening technique for early diagnosis of diseases, especially lung cancer. However, the technique provides insufficient accuracy because ...the exhaled air has many crucial volatile organic compounds (VOCs) at very low concentrations (ppb level). We analyzed the breath exhaled by lung cancer patients and healthy subjects (controls) using gas chromatography/mass spectrometry (GC/MS), and performed a subsequent statistical analysis to diagnose lung cancer based on the combination of multiple lung cancer-related VOCs. We detected 68 VOCs as marker species using GC/MS analysis. We reduced the number of VOCs and used support vector machine (SVM) algorithm to classify the samples. We observed that a combination of five VOCs (CHN, methanol, CH₃CN, isoprene, 1-propanol) is sufficient for 89.0% screening accuracy, and hence, it can be used for the design and development of a desktop GC-sensor analysis system for lung cancer.
•Catalyst on the micro-TGS lowers the temperature and induces a biased voltage.•Additive process of alumina dots changed the heat balance to controls the voltage.•Heat transfer analysis by FEM ...modeling is performed to control the heat balance.
A micro-thermoelectric gas sensor (micro-TGS) uses thermoelectric voltage induced by the catalytic combustion of hydrogen or methane for selective gas detection in breath. This is accomplished under an elevated temperature using a micro-heater built on the same membrane as a hotplate, which enables selective combustion of the target gas. A temperature differential built by the catalyst on the membrane induces the offset voltage (Voff) of the micro-TGS, which limits the amplifier circuit application. In this study, we strived to suppress Voff by an additive integration process of heat dissipation dots prepared using α-Al2O3 paste. In this paper, we discuss the effects of these α-Al2O3 dots on the thermal balance over the micro-TGS membrane by finite element method (FEM) modeling. When the dots were deposited in a symmetrical position to the combustion catalyst, Voff was compensated depending on the size, numbers, and locations of the dots. The micro-TGS heat transfer control by the dots was additionally verified by 3-D FEM modeling. The changes in Voff by the α-Al2O3 dots in FEM modeling were greater than those of the experiments, suggesting the high thermal conductivity of the micro-TGS membrane. The deviation of the membrane thermal conductivity due to the process non-uniformity significantly influenced the Voff; however, it was effectively reduced by the additive integration of dots.
Fix and flap surgery is the standard treatment for severe open-limb fractures. In cases of complex injuries, secondary surgeries such as additional osteosynthesis, implant removal, bone grafting, and ...debulking surgery may be required after the soft tissue condition has stabilized. During secondary surgery, if the nutrient vessels of the flap are resected haphazardly and an additional procedure is performed, flap necrosis may occur owing to insufficient blood flow. Creating a hemodynamic system that can withstand secondary surgery through increasing blood flow surrounding the flap is necessary in preventing necrosis. We report a case in which “provisional resection” of the nutrient artery was performed prior to the debulking surgery of a free anterolateral thigh flap.
A 45-year-old man sustained an extensive degloving injury on the dorsum of the hand during a car accident. On the fifth day after injury, soft tissue reconstruction with a free anterolateral thigh flap was performed. Although the soft tissue condition was stable, debulking surgery was planned 4 months after the injury because of the thickness of the flap. Flap necrosis may occur if the nutrient artery was resected and debulking surgery was performed simultaneously. Therefore, staged surgery using “provisional resection” of the nutrient artery was selected. First, the nutrient artery was resected. After waiting for 1 week, skin graft removal and flap thinning were performed as the second step. No flap necrosis was observed.
“Provisional resection” changes the hemodynamics of the flap to a random pattern due to the delay phenomenon and can prevent flap necrosis caused by secondary surgeries, such as debulking surgery.
Wet anisotropic etching based silicon micromachining is an important technique to fabricate freestanding (e.g. cantilever) and fixed (e.g. cavity) structures on different orientation silicon wafers ...for various applications in microelectromechanical systems (MEMS). {111} planes are the slowest etch rate plane in all kinds of anisotropic etchants and therefore, a prolonged etching always leads to the appearance of {111} facets at the sidewalls of the fabricated structures. In wet anisotropic etching, undercutting occurs at the extruded corners and the curved edges of the mask patterns on the wafer surface. The rate of undercutting depends upon the type of etchant and the shape of mask edges and corners. Furthermore, the undercutting takes place at the straight edges if they do not contain {111} planes. {100} and {110} silicon wafers are most widely used in MEMS as well as microelectronics fabrication.
This paper reviews the fabrication techniques of convex corner on {100} and {110} silicon wafers using anisotropic wet chemical etching. Fabrication methods are classified mainly into two major categories:
corner compensation method
and
two-steps etching technique
. In corner compensation method, extra mask pattern is added at the corner. Due to extra geometry, etching is delayed at the convex corner and hence the technique relies on time delayed etching. The shape and size of the compensating design strongly depends on the type of etchant, etching depth and the orientation of wafer surface. In this paper, various kinds of compensating designs published so far are discussed.
Two-step etching method
is employed for the fabrication of perfect convex corners. Since the perfectly sharp convex corner is formed by the intersection of {111} planes, each step of etching defines one of the facets of convex corners. In this method, two different ways are employed to perform the etching process and therefore can be subdivided into two parts. In one case, lithography step is performed after the first step of etching, while in the second case, all lithography steps are carried out before the etching process, but local oxidation of silicon (LOCOS) process is done after the first step of etching. The pros and cons of all techniques are discussed.
There are few reports of traumatic arterial spasm in large-sized vessels in the extremities, and many surgeons are skeptical of its existence. We report a case of traumatic popliteal artery injury ...(PAI), which was later diagnosed as traumatic popliteal artery spasm on intraoperative angiography.
A male patient, aged 54 years, was injured when a heavy object weighing approximately 100 kg fell on his right knee. Three hours after the injury, the patient was transported to our trauma center. The dorsalis pedis and posterior tibial arteries were not palpable, and his right lower leg was cold. However, he could move his ankle and toes completely and had no numbness or paresthesia in his right lower limb. Computed tomography angiography showed an interruption of the popliteal artery at the knee joint level and an enhancement on the distal side of the injury site. We diagnosed lower limb ischemia resulting from PAI and operated for revascularization.
Under general anesthesia, the popliteal artery was explored via a posterior S-shaped incision in the prone position. No arterial abnormalities were observed macroscopically, and the injured area remained unidentified. Therefore, a contrast medium was injected into the popliteal artery using a 20-gauge intravascular needle, and angiography was performed, which revealed that the popliteal artery was patent; however, there was circumferential arterial stenosis at the level of the knee joint. At this point, the right lower limb's coldness had disappeared. Arterial spasm was speculated to cause the transient popliteal occlusion and lower leg ischemia.
Immediate revascularization should be attempted when PAI is suspected. If no gross vascular abnormalities are confirmed, intraoperative angiography is useful for diagnosing arterial spasm.
•Traumatic arterial spasm in large-sized vessels in the extremities is rare.•Popliteal artery spasm associated with blunt trauma caused transient ischemia.•Computed tomography angiography showed the popliteal artery injury (PAI).•Immediate revascularization should be attempted when PAI is suspected.•Intraoperative angiography is useful to diagnose popliteal artery spasm.
We prepared 0.1 wt%-30 wt% Pd-loaded Co3O4 by a colloidal mixing method and investigated the sensing properties of a Pd-loaded Co3O4 sensor element, such as the sensor response, 90% response time, ...90% recovery time, and signal-to-noise (S/N) ratio, toward low nitric oxide (NO) gas levels in the range from 50 to 200 parts per billion. The structural properties of the Pd-loaded Co3O4 powder were investigated using X-ray diffraction analysis and transmission electron microscopy. Pd in the powder existed as PdO. The sensor elements with 0.1 wt%-10 wt% Pd content have higher sensor properties than those without any Pd content. The response of the sensor element with a 30 wt% Pd content decreased markedly because of the aggregation and poor dispersibility of the PdO particles. High sensor response and S/N ratio toward the NO gas were achieved when a sensor element with 10 wt% Pd content was used.
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