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Micromachined ZnO Piezoelectric Pressure Sensor and Pyroelectric Infrared Detector in GaAs
Jun Rim Choi,Pyung Choi 한국정보과학회 1998 Journal of Electrical Engineering and Information Vol.3 No.2
Piezoelectric pressure sensors and pyroelectric infrared detectors based on ZnO thin film have been integrated with GaAs metal-semiconductor field effect transistor (MESFET) amplifiers. Surface micromachining techniques have been applied in a GaAs MESFET process to form both microsensors and electronic circuits. The on-chip integration of microsensors such as pressure sensors and infrared detectors with GaAs integrated circuits is attractive because of the higher operating temperature up to 200 oC for GaAs devices compared to 125 oC for silicon devices and radiation hardness for infrared imaging applications. The micorsensors incorporate a 1 μm-thick sputtered ZnO capacitor supported by a 2 μ m-thick aluminum membrane formed on a semi-insulating GaAs substrate. The piezoelectric pressure sensor of an area 80 × 80 μ m2 designed for use as a miniature microphone exhibits 2.99 μ V/ μ bar sensitivity at 400 Hz. The voltage responsivity and the detectivity of a single infrared detector of an area 80 × 80 μ m2 is 700 V/W and 6 × 108 cmㆍ√Hz/W at 10 Hz respectively, and the time constant of the sensor with the amplifying circuit is 53 ms. Circuits using 4μm-gate GaAs MESFETs are fabricated in planar, direct ion-implanted process. The measured transconductance of a 4 μm - gate GaAs MESFET is 25.6 mS/mm and 12.4 mS/mm at 27 oC and 200 oC, respectively. A differential amplifier whose voltage gain is 33.7 dB using 4 μm gate GaAs MESFETs is fabricated for high selectivity to the physical variable being sensed.
Mutations of <i>ADAMTS9</i> Cause Nephronophthisis-Related Ciliopathy
Choi, Yo Jun,Halbritter, Jan,Braun, Daniela A.,Schueler, Markus,Schapiro, David,Rim, John Hoon,Nandadasa, Sumeda,Choi, Won-il,Widmeier, Eugen,Shril, Shirlee,Kö,rber, Friederike,Sethi, Sidharth K. Elsevier 2019 American journal of human genetics Vol.104 No.1
<P>Nephronophthisis-related ciliopathies (NPHP-RCs) are a group of inherited diseases that are associated with defects in primary cilium structure and function. To identify genes mutated in NPHP-RC, we performed homozygosity mapping and whole-exome sequencing for >100 individuals, some of whom were single affected individuals born to consanguineous parents and some of whom were siblings of indexes who were also affected by NPHP-RC. We then performed high-throughput exon sequencing in a worldwide cohort of 800 additional families affected by NPHP-RC. We identified two <I>ADAMTS9</I> mutations (c.4575_4576del [p.Gln1525Hisfs<SUP>∗</SUP>60] and c.194C>G [p.Thr65Arg]) that appear to cause NPHP-RC. Although ADAMTS9 is known to be a secreted extracellular metalloproteinase, we found that ADAMTS9 localized near the basal bodies of primary cilia in the cytoplasm. Heterologously expressed wild-type ADAMTS9, in contrast to mutant proteins detected in individuals with NPHP-RC, localized to the vicinity of the basal body. Loss of ADAMTS9 resulted in shortened cilia and defective sonic hedgehog signaling. Knockout of <I>Adamts9</I> in IMCD3 cells, followed by spheroid induction, resulted in defective lumen formation, which was rescued by an overexpression of wild-type, but not of mutant, ADAMTS9. Knockdown of <I>adamts9</I> in zebrafish recapitulated NPHP-RC phenotypes, including renal cysts and hydrocephalus. These findings suggest that the identified mutations in <I>ADAMTS9</I> cause NPHP-RC and that ADAMTS9 is required for the formation and function of primary cilia.</P>
최준림 ( Jun Rim Choi ) 한국센서학회 1998 센서학회지 Vol.7 No.2
Pyroelectric infrared detectors based on La-modified PbTiO₃ (PLT) thin films have been fabricated by RF magnetron sputtering and micromachining technology. The detectors form Pbi_(1-x)La_xTi_(1-x/4)O₃ (x=0.05) thin film ferroelectric capacitors epitaxially grown by RF magnetron sputtering on Pt/MgO (100) substrate. The sputtered PLT thin film exhibits highly c-axis oriented crystal structure that no poling treatment for sensing applications is required. This is an essential factor to increase the yield for realization of an infrared image sensor. Micromachining technology is used to lower the thermal mass of the detector by giving maximum sensor efficiency. Polyimide is coated on top of the sensing elements to support the fragile structure and the backside of the Mg0 substrate is selectively etched to reduce the heat loss. The sensing element exhibited a very high detectivity D* of 8.5x10^8 cm·√ Hz/W at room temperature and it is about 100 times higher than the case of micromachining technology is not used. A sensing system that detects the position as well as the existence of a human body is realized using the array sensor.