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Min, Sungjoon,Kim, Joonhyub,Park, Chanwon,Jin, Joon-Hyung,Min, Nam Ki Elsevier BV * North-Holland 2017 Applied Surface Science Vol.410 No.-
<P><B>Abstract</B></P> <P>Single-walled carbon nanotube (SWCNT) networks are subjected to a low-powered oxygen plasma for the surface modification. Changes in the surface chemical composition and the stability of the plasma-treated SWCNT (p-SWCNT) with aging in air for up to five weeks are studied using X-ray photoelectron spectroscopy (XPS) and contact angle analysis. The contact angle decreases from 120° of the untreated hydrophobic SWCNT to 0° for the superhydrophilic p-SWCNT. Similarly, the ratio of oxygen to carbon (O:C) based on the XPS spectra increases from 0.25 to 1.19, indicating an increase in surface energy of the p-SWCNT. The enhanced surface energy is gradually dissipated and the p-SWCNT network loses the superhydrophilic surface property. However, it never revert to the original hydrophobic surface state but to a metastable hydrophilic state. The aging effect on sensitivity of the p-SWCNT network-based ammonia sensor is investigated to show the importance of the aging process for the stabilization of the p-SWCNT. The best sensitivity for monitoring NH<SUB>3</SUB> gas is observed with the as-prepared p-SWCNT, and the sensitivity decreases as similar as the p-SWCNT loses its hydrophilicity with time goes by. After a large performance degradation during the aging time for about two weeks, the response characteristics including sensitivity and response time of the p-SWCNT to ammonia gas are stabilized and eventually saturated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Superhydrophilic single-walled carbon nanotube network can be obtained by O<SUB>2</SUB> plasma-based surface modification. </LI> <LI> The modified carbon nanotube surface invariably reverts to a metastable state in a non-reversible manner. </LI> <LI> Aerobic aging is essential to stabilize the modified carbon nanotube and the carbon nanotube-based sensing device due to minimized sensor-to-sensor variation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Superhydrophilic single-walled carbon nanotube obtained by O<SUB>2</SUB> plasma treatment voluntarily and non-reversibly reverts to a metastable state. This aerobic aging is an essential process to develop a stable carbon nanotube-based sensor.</P> <P>[DISPLAY OMISSION]</P>
Su Chak Ryu,JoonHyub Kim,Woo Sob Sim,김승현 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.4
This study aimed to develop prosthetic foot for the low-income class. Considering that the prosthetic foot was manufactured through 3D printing, we tested whether the material used can be used for such application. Through load-added simulation, a safety factor of at least 6 was measured. The results show that it can be introduced into the prosthetic foot. An ankle multi-axis rotation device, metatarsal head, and toe joint were introduced for comfortable walking of the patient. The muscle power required for walking was simulayed by conducting a load test of the corresponding motion. The prosthetic foot simulated a muscle power of 1263.56 N through the ankle device and 25.7 N·m through the toe joint. Therefore, the actual human body had a value exceeding the muscle power of 1058.90 N and 20.2 N·m, which would help the wearer’s walking.