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Effects of Hardness on the Sensitivity and Load Capacity of 3D Printed Sensors
Myoeum Kim,Daryl George Philip,Md. Omar Faruk Emon,Jae-Won Choi 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.3
One recent success of additive manufacturing (AM; also known as 3D printing) technologies is a 3D printed pressuresensitive sensor (i.e. tactile sensor) with a greater degree of design complexity and multi-material components. Although 3D printed pressure sensors have been realized, there still exists a topic of extensive ongoing research. This study aimed to investigate the effects of hardness of the 3D printed sensors on characteristics such as the sensitivity and load capacity of the sensors. The ultimate goal of this work is to provide guidelines for selecting hardness for 3D printed sensors used in different sensor applications (i.e., soft and highly sensitive humanoid hands vs. less soft and less sensitive industrial robotic hands). A multi-material direct-print photopolymerization (DPP) process was used to produce an entire sensor that consists of insulating layers, electrode layers, and a pressure-sensitive layer. Soft and rigid photopolymers were blended to achieve six different hardness levels such as Shore A of 50, 60, 70, 85, 95 and 98. A carbon nanotube/polymer composite was used to create the electrodes, and 1-ethyl-3-methylimidazolium tetrafluoroborate as an ionic liquid was used with a photopolymer for the pressure-sensitive layer. Sensors of different hardness were tested by applying varying loads using a force gauge, and sensor signals were collected. Soft sensors with Shore A hardness of 50, 60 and 70 showed reliable outputs, where the softer sensor provided better sensitivity and smaller errors but lower load capacity. Sensors with Shore A of 85, 95 and 98 did not show reliable outputs, where the harder insulating layer did not allow the force gauge to press into the sensor, instead causing the gauge to slip over the surface. These findings could be useful for designing customized sensors for applications with different load conditions.
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Kim, Myoeum,Eo, Kyoungbok,Lim, Hyun Jun,Kwon, Yong Ku Elsevier 2018 Composites science and technology Vol.165 No.-
<P><B>Abstract</B></P> <P>Low shrinkage, mechanically-strong polyimide hybrid aerogels were synthesized using a supercritical carbon dioxide (scCO<SUB>2</SUB>) drying process. Polyimide hybrid aerogels of biphenyl tetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) containing surface-modified hollow mesoporous silica (AHMS) nanoparticles were prepared by chemical imidization and scCO<SUB>2</SUB> drying. To avoid the high volume shrinkage of wet gels that occurs mainly during the drying process, AHMS nanoparticles were introduced to the network structure of the PI aerogels as a crosslinker. All aerogels exhibited a highly-interconnected, network-like structure of polyimide nanofibers with an average fiber diameter of approximately 27.6 nm and 92.8% porosity. These hybrid aerogels exhibited an excellent compression modulus, thermal stability, and high surface area, as well as low density, low shrinkage, and low thermal conductivity.</P>
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고분자/은 혼성 나노입자의 제조 및 표면 플라즈몬 공명 현상
어경복(Kyoungbok Eo),김묘음(Myoeum Kim),임현준(Hyunjoon Ihm),정소연(Soyeon Jeong),권용구(Yong Ku Kwon) 한국고분자학회 2018 폴리머 Vol.42 No.1
단분산성 스타이렌-염화비닐벤젠 공중합체(PSBC) 나노입자의 표면을 개질하고 AgNO3과의 반응을 통하여 Ag 나노입자가 고정화된 100-200 nm 평균 입자직경을 가지는 Ag-고분자 혼성 나노입자를 제조한다. 먼저 무유화 에멀젼 중합 방법을 이용하여 단분산성 PSBC 공중합체 나노입자를 합성한 뒤, 이들 나노입자 표면의 chlorine그룹을 thiourea 등을 이용하여 thiol기로 변화, 개질(PSBSH)한다. 이들 PSBSH 고분자 나노입자와 AgNO3와의 반응을 통하여 Ag입자가 표면에 고정화된 고분자-Ag 복합체(PSBAg) 나노입자를 제조하였다. Ag입자의 고정화 과정은 PSBSH 나노입자 표면에서 Ag+ 이온과 표면의 thiol기와의 반응을 통하여 강한 Ag-S- 결합을 형성하고 반데르발스 힘에 의해 Ag 이온들이 고분자 표면에서 환원되면서 Ag 입자가 고정화된 PSBAg 복합나노입자를 제조하였다. 고분자 표면에 은 나노 입자들이 고정된 형태의 나노 복합체의 합성과 표면구조는 SEM, TEM, XRD, FTIR, UV-Vis spectroscopy 등 다양한 분석 방법을 확인하였고, PSBAg 복합나노입자는 표면에 존재하는 Ag 입자로부터 비롯된 표면 플라즈몬 공명(SPR) 현상을 확인할 수 있었고 고분자 입자의 크기와 PSBSH 고분자에 고정된 Ag 나노입자의 함량의 변화에 따른 SPR 현상의 변화를 관찰하였다. Hybrid polymeric nanoparticles containing metal silver nanoparticles were successfully synthesized. Monodisperse poly(styrene-co-vinylbenzyl chloride) (PSBC) nanoparticles with an average diameter of 100-200 nm were synthesized by surfactant-free emulsion polymerization. The chlorine group on the surfaces of the PSBC nanoparticles was converted into thiol group by surface modification with thiourea. The thiol groups of the surface-modified nanoparticles with thiol group (PSBSH) were reacted with Ag+ ions to form Ag-S bonds and then produce the PSBAg hybrid nanoparticles containing Ag nanoparticles, intercalatedon to the surfaces through reduction. The successful immobilization of Ag onto the surface of the polymer nanoparticles was confirmed using various characterization tools. The surface plasmon resonance (SPR) was observed from the Ag nanoparticles of the PSBAg nanoparticles. By varying the size of the polymer nanoparticles and the amount of silver adhered onto them, the surface plasmon resonance of the nanocomposite materials was investigated.
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Yoon, Ji Yeon,Eo, Kyoungbok,Kim, Myoeum,Kwon, Yong Ku Elsevier 2018 Polymer Vol.138 No.-
<P><B>Abstract</B></P> <P>A series of novel conjugated copolymers of poly[(3-alkylthiophene-2,5-diyl)-<I>alt</I>- (3-cyanothiophene-2,5-diyl)]s, (PACTs), containing electron-releasing 3-alkylyl thiophene-2,5-diyl (AT) and electron-withdrawing dibromo 3-cyanothiophene- 2, 5-diyl (CT) were synthesized by the polycondensation of a direct heteroarylation reaction. The regular alteration of the electron donor and electron acceptor unit in a polymer backbone led to a decrease in the energy bandgap of conjugated poly(3-alkylylthiophene-2,5-diyl)s (P3HT). To accelerate the polycondensation reaction, microwave-assisted heating was used to reduce the reaction time and increase the molecular weight of the polymers. Owing to the strong intermolecular interactions between the neighboring 3-cyanothiophene-2,5-diyl units in the polymer backbone, the lamellar and edge-on structures of the polymer chains were induced on the substrate. The photovoltaic performance of these conjugated copolymers was also evaluated by preparing bulk heterojunction solar cell devices of ITO/PEDOT: PSS/PACT:PC<SUB>71</SUB>BM/Al.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A series of novel low bandgap conjugated polymers were synthesized <I>via</I> direct heteroarylation. </LI> <LI> The introduction of cyanothiophene in poly(3-alkylthiophene)s reduced the energy bandgap. </LI> <LI> The lamellar and edge-on structures of the polymer chains were induced on the substrate. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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