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Mohammad Shamim Reza,Kevin Ray Ayag,유미경,김갑진,김홍두 한국섬유공학회 2019 Fibers and polymers Vol.20 No.2
Electrospun Spandex nanofiber webs having very high amount of nano-sized open cell can be used as a piezocapacitive sensor for monitoring both static and dynamic pressures due to excellent electrospinnability and very good elastic properties. Compared to our previously reported SBS and TPU electrospun nanoweb, Spandex showed relatively linearincrease of capacitance with applied pressure and restored its initial thickness when the pressure was released due to the improved resilience and elasticity. Moreover, small amount of ionic liquid (IL) was added in Spandex dope solution to increase the sensitivity of sensor to pressure, which induced very large amount of capacitance change with pressure, as well as reducing the capacitance-pressure hysteresis. In this work, hysteresis of the sensor was assessed through measuring the capacitance values during 20 cyclic loading and unloading and was improved significantly from 7.5 % to 1.8 %. Creep andstress relaxation behaviors were also tested through measuring capacitance under the constant loading and loading under the constant capacitance as a function of time respectively, using a dynamic pressure tester and an LCR meter. The results are reported in detail.
Mohammad Shamim Reza,김갑진,김홍두 한국섬유공학회 2020 Fibers and polymers Vol.21 No.12
In this study, the mixture solution of Spandex and polyvinylidene fluoride (PVDF) was electrospun undercontrolled compositions to obtain Spandex-PVDF hybrid nanofiber webs. Their physico-mechanical and piezo-responsivebehaviors were investigated. When the dynamically changing force was applied to this hybrid sensor, dynamic pressure couldbe measured through the electric current generated by the orientational change of C-F dipoles in the PVDF part of thecomposite nanoweb as a function of time. When the static force was applied to this hybrid sensor, static pressure could bemeasured through the increasing capacitance value caused by the decreasing thickness of the composite nanoweb rather thanthe piezoelectric current. The piezoelectric and piezocapacitive properties of this hybrid sensor could be measuredsimultaneously using a piezoelectric amplifier and an LCR meter, respectively. Overall, 25-50 wt.% addition of PVDF inSpandex greatly enhanced the piezoelectric output signal as well as reduced pressure-capacitance hysteresis and highercapacitance change with the applied pressure due to the rubbery Spandex of this hybrid sensor. Moreover, AgNO3, which actsas a precursor of silver nano-particle (AgNP) formed in the electrospun PVDF nanoweb, was added into the PVDF/Spandexelectrospun solution to get enhanced piezoelectric performance of the hybrid sensor caused by the preferential formation of β-phase of PVDF. The results are reported in detail.
Polyurethane/Polyvinylidene Fluoride Blend Electrospun Nanofiber Web Based Hybrid Tactile Sensor
Reza Mohammad Shamim,Mir Muhammad Fahad,Gajula Prasad,Sellamuthu N. Jaisankar,김갑진,김홍두 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2
Electrospun polyurethane (PU) nanofiber webs (NFw) having very high amount of nano-sized open cell can be used as a piezo-capacitive sensor due to excellent electrospinnability and very good elastic properties that has been reported in our previous study. In contrast, electrospun PVDF exhibits high β-crystalline phase content and superior piezoelectricity. Consequently, in this study, PU/PVDF blends under controlled compositions were electrospun to obtain PU/PVDF hybrid NFw. These hybrid sensors are capable of measuring piezocapacitive properties as well as simultaneously piezoelectric properties. Moreover, AgNO₃ was added into PVDF e-spun solution which acts as Ag-NPs in PVDF NFw to get enhanced piezoelectric performance of the hybrid sensor. Around 25% addition of PVDF into PU solution in the presence of Ag-NPs greatly enhance the peak-to-peak piezoelectric output voltage (Vp-p) along with 4.2% hysteresis and pressure-capacitance change of over 55 pF.