Browsing by Author "Kim, Seon Jeong"
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Item Bio-Inspired, Moisture-Powered Hybrid Carbon Nanotube Yarn MusclesKim, Shi Hyeong; Kwon, Cheong Hoon; Park, Karam; Mun, Tae Jin; Lepro, Xavier; Baughman, Ray H.; Spinks, Geoffrey M.; Kim, Seon Jeong; 0000 0003 5232 4253 (Baughman, RH); 0000-0002-0166-3127 (Lepró, X); Lepró, Xavier; Baughman, Ray H.Hygromorph artificial muscles are attractive as self-powered actuators driven by moisture from the ambient environment. Previously reported hygromorph muscles have been largely limited to bending or torsional motions or as tensile actuators with low work and energy densities. Herein, we developed a hybrid yarn artificial muscle with a unique coiled and wrinkled structure, which can be actuated by either changing relative humidity or contact with water. The muscle provides a large tensile stroke (up to 78%) and a high maximum gravimetric work capacity during contraction (2.17 kJ kg⁻¹), which is over 50 times that of the same weight human muscle and 5.5 times higher than for the same weight spider silk, which is the previous record holder for a moisture driven muscle. We demonstrate an automatic ventilation system that is operated by the tensile actuation of the hybrid muscles caused by dew condensing on the hybrid yarn. This self-powered humidity-controlled ventilation system could be adapted to automatically control the desired relative humidity of an enclosed space.Item Biothermal Sensing of a Torsional Artificial Muscle(Royal Soc Chemistry, 2016-01-25) Lee, Sung-Ho; Kim, Tae Hyeob; Lima, M©rcio D.; Baughman, Ray H.; Kim, Seon Jeong; 0000 0003 5232 4253 (Baughman, RH); Lima, M©rcio D.; Baughman, Ray H.Biomolecule responsive materials have been studied intensively for use in biomedical applications as smart systems because of their unique property of responding to specific biomolecules under mild conditions. However, these materials have some challenging drawbacks that limit further practical application, including their speed of response and mechanical properties, because most are based on hydrogels. Here, we present a fast, mechanically robust biscrolled twist-spun carbon nanotube yarn as a torsional artificial muscle through entrapping an enzyme linked to a thermally sensitive hydrogel, poly(N-isopropylacrylamide), utilizing the exothermic catalytic reaction of the enzyme. The induced rotation reached an equilibrated angle in less than 2 min under mild temperature conditions (25-37 ⁰C) while maintaining the mechanical properties originating from the carbon nanotubes. This biothermal sensing of a torsional artificial muscle offers a versatile platform for the recognition of various types of biomolecules by replacing the enzyme, because an exothermic reaction is a general property accompanying a biochemical transformation.Item Enhancement of Electromagnetic Interference Shielding Effectiveness with Alignment of Spinnable Multiwalled Carbon Nanotubes(Pergamon-Elsevier Science Ltd, 2018-10-23) Lee, Duck Weon; Park, Jongwoo; Kim, Bum Joon; Kim, Hyunsoo; Choi, Changsoon; Baughman, Ray H.; Kim, Seon Jeong; Kim, Youn Tae; 0000-0001-5845-5137 (Baughman, RH); Baughman, Ray H.This research develops a unique material to attenuate electromagnetic interference (EMI) by using spinnable multiwalled carbon nanotubes (MWNTs) combined with bio-polydimethylsiloxane (PDMS) that contains BaTiO₃ (MBPBT). In particular, a plaid pattern, formed by the spinnable MWNTs, is very effective in attenuating the propagation of EM waves, which achieves over 20 dB at 8.2-12.4 GHz (X-band frequency range). This means that a filter type of the spinnable MWNTs is actively able to handle the directionality and movement of EMI propagation. In addition, the MBPBT is characterized by its strong mechanical advantage (bending radius 180 degrees).Item Harvesting Electrical Energy from Torsional Thermal Actuation Driven by Natural Convection(Nature Publishing Group) Kim, Shi Hyeong; Sim, Hyeon Jun; Hyeon, Jae Sang; Suh, Dongseok; Spinks, Geoffrey M.; Baughman, Ray H.; Kim, Seon Jeong; 0000-0001-5845-5137 (Baughman, RH); Baughman, Ray H.; Kim, Seon JeongThe development of practical, cost-effective systems for the conversion of low-grade waste heat to electrical energy is an important area of renewable energy research. We here demonstrate a thermal energy harvester that is driven by the small temperature fluctuations provided by natural convection. This harvester uses coiled yarn artificial muscles, comprising well-aligned shape memory polyurethane (SMPU) microfibers, to convert thermal energy to torsional mechanical energy, which is then electromagnetically converted to electrical energy. Temperature fluctuations in a yarn muscle, having a maximum hot-to- cold temperature difference of about 13 ⁰C, were used to spin a magnetic rotor to a peak torsional rotation speed of 3,000 rpm. The electromagnetic energy generator converted the torsional energy to electrical energy, thereby producing an oscillating output voltage of up to 0.81 V and peak power of 4 W/kg, based on SMPU mass.Item Harvesting Temperature Fluctuations as Electrical Energy Using Torsional and Tensile Polymer Muscles(Royal Soc Chemistry, 2015-09-28) Kim, Shi Hyeong; Lima, M©rcio D.; Kozlov, Mikhail E.; Haines, Carter S.; Spinks, Geoffrey M.; Aziz, Shazed; Choi, Changsoon; Sim, Hyeon Jun; Wang, Xuemin; Lu, Hongbing; Qian, Dong; Madden, John D. W.; Baughman, Ray H.; Kim, Seon Jeong; 0000 0003 5232 4253 (Baughman, RH); Lima, M©rcio D.; Kozlov, Mikhail E.; Wang, Xuemin; Lu, Hongbing; Qian, Dong; Baughman, Ray H.Diverse means have been deployed for harvesting electrical energy from mechanical actuation produced by low-grade waste heat, but cycle rate, energy-per-cycle, device size and weight, or cost have limited applications. We report the electromagnetic harvesting of thermal energy as electrical energy using thermally powered torsional and tensile artificial muscles made from inexpensive polymer fibers used for fishing line and sewing thread. We show that a coiled 27 μm-diameter nylon muscle fiber can be driven by 16.7 ⁰C air temperature fluctuations to spin a magnetic rotor to a peak torsional rotation speed of 70000 rpm for over 300000 heating-cooling cycles without performance degradation. By employing resonant fluctuations in air temperature of 19.6 ⁰C, an average output electrical power of 124 W per kg of muscle was realized. Using tensile actuation of polyethylene-based coiled muscles and alternating flows of hot and cold water, up to 1.4 J of electrical energy was produced per cycle. The corresponding per cycle electric energy and peak power output, per muscle weight, were 77 J kg⁻¹ and 28 W kg⁻¹, respectively.Item Highly Stretchable Hybrid Nanomembrane Supercapacitors(2016-03-04) Kim, Keon Jung; Lee, Jae Ah (UT Dallas); Lima, Márcio D. (UT Dallas); Baughman, Ray H.; Kim, Seon Jeong; 0000 0003 5232 4253 (Baughman, RH); Baughman, Ray H.Supercapacitors that are lightweight, mechanically deformable (stretchable, flexible) and electrochemically stable have potential for various applications like portable, wearable, and implantable electronics. Here we demonstrate a stretchable and high-performing hybrid nanomembrane supercapacitor. The hybrid nanomembrane is prepared by vapour phase polymerization (VPP) based nanoscopic PEDOT coating on carbon nanotube sheets (CNS) transferred onto an elastomeric substrate to form a wavy structure. The resulting wavy structured hybrid nanomembrane based supercapacitor exhibits high electrochemical performance and mechanical stretchability, simultaneously. The high specific capacitances and energy density (82 F g⁻¹, 11 mF cm⁻², and 7.28 W h kg⁻¹ at 0% strain) are retained under large mechanical deformation (77 F g⁻¹ and 6.87 W h kg⁻¹ at a biaxial strain of 600%). Moreover, there is only <1% degradation of capacitance ratio after 1000 cycles stretching/releasing and bending/unbending. This high mechanical cyclic stability is shown even during stretching/releasing and bending/unbending measured by dynamic cyclic voltammetry (CV). These results suggest that our supercapacitor is valuable in a wide range of applications that require it to be electrochemically stable under large mechanical deformation, such as strain sensors, wearable electronics and biomedical devices.Item Shape-Engineerable Composite Fibers and Their Supercapacitor Application(RSC Pub, 2016-01-12) Kim, Kang Min; Lee, Jae Ah ((UT Dallas); Sim, Hyeon Jun; Kim, Kyung-Ah; Jalili, Rouhollah; Spinks, Geoffrey M.; Kim, Seon JeongDue to excellent electrical and mechanical properties of carbon nano materials, it is of great interest to fabricate flexible, high conductive, and shape engineered carbon based fibers. As part of these approaches, hollow, twist, ribbon, and other various shapes of carbon based fibers have been researched for various functionality and application. In this paper, we suggest simple and effective method to control the fiber shape. We fabricate the three different shapes of hollow, twisted, and ribbon shaped fibers from wet spun giant graphene oxide (GGO)/single walled-nanotubes (SWNTs)/poly(vinyl alcohol) (PVA) gels. Each shaped fibers exhibit different mechanical properties. The average specific strengthes of the hollow, twist, and ribbon fibers presented here are 126.5, 106.9, and 38.0 MPa while strain are 9.3, 13.5, and 5%, respectively. Especially, the ribbon fiber shows high electrical conductivity (524 ± 64 S cm⁻¹) and areal capacitance (2.38 mF cm⁻²).