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Designing a nanocrystal-based temperature and strain multi-sensor with one-step inkjet printing
( Junsung Bang ),( Junhyuk Ahn ),( Soong Ju Oh ) 한국센서학회 2021 센서학회지 Vol.30 No.4
Wearable multi-sensors based on nanocrystals have attracted significant attention, and studies on patterning technology to implement such multi-sensors are underway. Conventional patterning processes may affect material properties based on high temperatures and harsh chemical conditions. In this study, we developed an inkjet printing technique that can overcome these drawbacks through the application of patterning processes at room temperature and atmospheric pressure. Nanocrystal-based ink is used to adjust properties efficiently. Additionally, the viscosity and surface tension of the solvents are investigated and optimized to increase patterning performance. In the patterning process, the electrical, electrothermal, and electromechanical properties of the nanocrystal pattern are controlled by the ligand exchange process. Experimental results demonstrate that a multi-sensor with a temperature coefficient of resistance of 3.82 × 10<sup>-3</sup> K<sup>-1</sup> and gauge factor of 30.6 can be successfully fabricated using one-step inkjet printing.
Self-calibrated Mueller-Matrix Spectroscopic Ellipsometry
kyoung-yoon Bang,ilsin an,Junsung An,robert collins 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.1
The Mueller matrix spectroscopic ellipsometer was developed in a dual-rotating-compensator conguration. Instead of continuous rotation and integration for waveform analysis, a step-and-scan method was adopted for both compensators and Fourier analysis was used for waveform analysis. With this method, complicated control of the rotational speed and the phase between the two compensators could be avoided. For the preliminary diagnosis of the system, self-calibration was performed in the transmission mode. For vanishing Fourier coecients, almost null values were obtained, with a standard deviation of 0.001. From non-vanishing terms, reasonable results were obtained for the retardance and angular oset for each optical element.
안준혁,Choi Hyung Jin,Bang Junsung,손가연,오승주 나노기술연구협의회 2022 Nano Convergence Vol.9 No.46
Human voice recognition techniques have remarkable potential for clinical applications because information from acoustic signals can reflect human body conditions. This paper reports the fabrication of Ag nanocrystal (NC)-based multiaxial wearable strain gauge sensors by ink-lithography for voice recognition systems. Benefiting from the onestep-device-fabrication strategy of ink-lithography, which can yield Ag NC patterns with specific dimensions and endow physical properties, the Ag NC-based multiaxial strain sensors can be fabricated on an ultrathin substrate (~ 6 μm). Additionally, the coffee-ring effect can be induced onto the Ag NC patterns to realize high sensitivity and angle dependence (gauge factors G 0 ◦ = 11.7 ± 1.2 and G 90 ◦ = 105.5 ± 20.1); moreover, the voice onset time for voice recognition can be detected by the sensors. These features assist in distinguishing between voiced and voiceless plosive contrasts via measurements of contact-based voice onset time differences and can act as a cornerstone for further advancements in wearable sensors as well as voice recognition and analysis.
Woo, Ho Kun,Kim, Haneun,Jeon, Sanghyun,Lee, Woo Seok,Ahn, Junhyuk,Bang, Junsung,Kang, Min Su,Oh, Soong Ju The Royal Society of Chemistry 2019 Journal of Materials Chemistry C Vol.7 No.17
<P>Highly transparent and sensitive pressure sensors with a wide detection range were developed by a simple process using silver nanowires and ZnO nanocrystals (NCs) without lithography. The open mesh structured spacers were sucessfully designed by one-step chemical treatment involving a ligand exchange process on the ZnO NC thin films, leading to improved sensitivity, responsivity and transparency. The device performance analyses along with chemical, structural, and electronic characterization studies reveal that the chemically designed pressure sensor has a record-breaking sensitivity of 3.23 × 10<SUP>3</SUP> kPa<SUP>−1</SUP>, a large detection range of up to 75 kPa, excellent reliability, and high transparency of 85% in the visible-light region. The origin of improved sensitivity was explained with the contact area variation theory. We also demonstrate that the pressure sensor fabricated by the all-solution-based facile process can be employed in various applications such as wearable sensors for measurement of the human pulse and attachable electronics for an electronic skin with a wide sensing range of pressures.</P>