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Nanocomposite Hydrogel with High Toughness for Bioactuators
Shin, Min Kyoon,Spinks, Geoffrey M.,Shin, Su Ryon,Kim, Sun I.,Kim, Seon Jeong WILEY-VCH Verlag 2009 Advanced Materials Vol.21 No.17
<B>Graphic Abstract</B> <P>Ferritin-based nanofibrous hydrogels that demonstrate synergy between the ferritin protein and the synthetic polymer matrix are fabricated. The hybrid hydrogels showed enhanced mechanical properties and repeated expansion and contraction without showing severe creep during pH switching. The ferritin nanoparticles incorporated into the hydrogel nanofibers improved the actuation stability of a hydrogel actuator by acting as elastic nanosprings in a nanoscale polymer. <img src='wiley_img/09359648-2009-21-17-ADMA200802205-content.gif' alt='wiley_img/09359648-2009-21-17-ADMA200802205-content'> </P>
Kim, Hyunsoo,Jalili, Rouhollah,Spinks, Geoffrey M.,Wallace, Gordon G.,Kim, Seon Jeong Elsevier 2017 Composites science and technology Vol.149 No.-
<P><B>Abstract</B></P> <P>Carbon fibers are well-known reinforcing elements in advanced composites, but these materials remain expensive partly due to the complex processing methods used to form high strength and high modulus fibers. Graphene is seen as an alternative precursor for the formation of high strength carbon-based fibers. Here it is shown that the strength and modulus of graphene-based fibers are enhanced by incorporating a polyacrylonitrile (PAN) binder, surface coating with polydopamine (PDA) and through appropriate pyrolysis heat treatments. Fiber samples were prepared by a wet-spinning method such that the composition of liquid-crystalline graphene oxide (LCGO) and PAN could be varied over the full range. The maximum fiber mechanical strength (220 MPa) and modulus (19 GPa) occurred at a composition of LCGO (80 wt%) and PAN (20 wt%). The mechanical strength was further significantly increased to 526 MPa through pyrolysis of the LCGO/PAN fiber at 800 °C in a nitrogen atmosphere which caused carbonization of PAN. In addition, surface treatment of the LCGO/PAN fiber with PDA before carbonization improved the mechanical strength by an additional 40%.</P>
Incidence of exercise-associated hyponatremia during a high-altitude 161-km ultramarathon
( Morteza Khodaee ),( Anahita Saeedi ),( Christine Harris-Spinks ),( Tamara Hew-Butler ) 한국운동영양학회 2021 Physical Activity and Nutrition (Phys Act Nutr) Vol.25 No.3
[Purpose] Exercise-associated hyponatremia (EAH) is a well-known condition among endurance athletes at low altitudes. The incidence of EAH during ultramarathons at high altitudes warrants further investigation. This prospective observational study was conducted on the participants of the Leadville Trail 100 run, a 161- km race held at a high altitude (2,800 m-3,840 m). [Methods] Venous blood samples were collected before and immediately after the race. The participants completed an electronic survey after the race. Our main outcome measure was the post-race serum sodium ([Na<sup>+</sup>]) level. [Results] Of the 672 athletes who started the race, 351 (52%) successfully completed the event within the 30- hour cut-off. Post-race blood samples were collected from 84 runners (66 finishers). Both pre- and post-race blood samples were collected from 37 participants. Twenty percent of the post-race participants had EAH. Only one post-race participant had a [Na<sup>+</sup>] level of <130 mmol/L. All participants with EAH were asymptomatic. One participant had an abnormal pre-race [Na<sup>+</sup>] level (134 mmol/L). Female participants had a significantly higher rate of EAH than male participants (40% vs. 16%; p=0.039). Age, body mass index, weight changes, race completion status, nonsteroidal anti-inflammatory drug use, and urine specific gravity were not associated with the development of EAH. Lower postrace [Na<sup>+</sup>] levels were associated with higher serum creatine kinase values (R<sup>2</sup>=0.1, p<0.005). [Conclusion] High altitude (3,840 m peak) does not appear to enhance the incidence of EAH after an ultramarathon footrace. This suggests that ambient temperature (low temperatures reduce risk), sex (female predilection), endurance running, and overhydration are more prominent risk factors for EAH than high altitude.
All-Solid-State Carbon Nanotube Torsional and Tensile Artificial Muscles
Lee, Jae Ah,Kim, Youn Tae,Spinks, Geoffrey M.,Suh, Dongseok,Lepró,, Xavier,Lima, Má,cio D.,Baughman, Ray H.,Kim, Seon Jeong American Chemical Society 2014 NANO LETTERS Vol.14 No.5
<P>We report electrochemically powered, all-solid-state torsional and tensile artificial yarn muscles using a spinnable carbon nanotube (CNT) sheet that provides attractive performance. Large torsional muscle stroke (53°/mm) with minor hysteresis loop was obtained for a low applied voltage (5 V) without the use of a relatively complex three-electrode electromechanical setup, liquid electrolyte, or packaging. Useful tensile muscle strokes were obtained (1.3% at 2.5 V and 0.52% at 1 V) when lifting loads that are ∼25 times heavier than can be lifted by the same diameter human skeletal muscle. Also, the tensile actuator maintained its contraction following charging and subsequent disconnection from the power supply because of its own supercapacitor property at the same time. Possible eventual applications for the individual tensile and torsional muscles are in micromechanical devices, such as for controlling valves and stirring liquids in microfluidic circuits, and in medical catheters.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-5/nl500526r/production/images/medium/nl-2014-00526r_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl500526r'>ACS Electronic Supporting Info</A></P>
Lee, Jae Ah,Shin, Min Kyoon,Kim, Shi Hyeong,Kim, Seon Jeong,Spinks, Geoffrey M.,Wallace, Gordon G.,Ovalle-Robles, Raquel,Lima, Má,rcio D.,Kozlov, Mikhail E.,Baughman, Ray H. American Chemical Society 2012 ACS NANO Vol.6 No.1
<P>We report mechanically robust, electrically conductive, free-standing, and transparent hybrid nanomembranes made of densified carbon nanotube sheets that were coated with poly(3,4-ethylenedioxythiophene) using vapor phase polymerization and their performance as supercapacitors. The hybrid nanomembranes with thickness of ∼66 nm and low areal density of ∼15 μg/cm<SUP>2</SUP>exhibited high mechanical strength and modulus of 135 MPa and 12.6 GPa, respectively. They also had remarkable shape recovery ability in liquid and at the liquid/air interface unlike previous carbon nanotube sheets. The hybrid nanomembrane attached on a current collector had volumetric capacitance of ∼40 F/cm<SUP>3</SUP> at 100 V s<SUP>–1</SUP> (∼40 and ∼80 times larger than that of onion-like carbon measured at 100 V s<SUP>–1</SUP> and activated carbon measured at 20 V s<SUP>–1</SUP>, respectively), and it showed rectangular shapes of cyclic voltammograms up to ∼5 V s<SUP>–1</SUP>. High mechanical strength and flexibility of the hybrid nanomembrane enabled twisting it into microsupercapacitor yarns with diameters of ∼30 μm. The yarn supercapacitor showed stable cycling performance without a metal current collector, and its capacitance decrease was only ∼6% after 5000 cycles. Volumetric energy and power density of the hybrid nanomembrane was ∼70 mWh cm<SUP>–3</SUP> and ∼7910 W cm<SUP>–3</SUP>, and the yarn possessed the energy and power density of ∼47 mWh cm<SUP>–3</SUP> and ∼538 W cm<SUP>–3</SUP>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-1/nn203640a/production/images/medium/nn-2011-03640a_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn203640a'>ACS Electronic Supporting Info</A></P>
Artificial Muscles from Fishing Line and Sewing Thread
Haines, Carter S.,Lima, Má,rcio D.,Li, Na,Spinks, Geoffrey M.,Foroughi, Javad,Madden, John D. W.,Kim, Shi Hyeong,Fang, Shaoli,Jung de Andrade, Mô,nica,Gö,ktepe, Fatma,Gö,ktepe, &Oum American Association for the Advancement of Scienc 2014 Science Vol.343 No.6173
<P><B>Toward an Artificial Muscle</B></P><P>In designing materials for artificial muscles, the goals are to find those that will combine high strokes, high efficiency, long cycle life, low hysteresis, and low cost. Now, <B>Haines <I>et al.</I></B> (p. 868; see the Perspective by <B>Yuan and Poulin</B>) show that this is possible. Twisting high-strength, readily available polymer fibers, such as those used for fishing lines or sewing thread, to the point where they coil up, allowed construction of highly efficient actuators that could be triggered by a number of stimuli.</P>
Fullerene Attachment Enhances Performance of a DNA Nanomachine
Shin, Su Ryon,Jin, Kyeong Sik,Lee, Chang Kee,Kim, Sun I.,Spinks, Geoffrey M.,So, Insuk,Jeon, Ju-Hong,Kang, Tong Mook,Mun, Ji Young,Han, Sung-Sik,Ree, Moonhor,Kim, Seon Jeong WILEY-VCH Verlag 2009 ADVANCED MATERIALS Vol.21 No.19
<B>Graphic Abstract</B> <P>Fullerene moieties are attached to single-strand DNA and the pH-induced conformational changes are evaluated in detail. It is found that fullerene attachments significantly enhance the machine performance of the DNA strand by stabilization of internal structure through intramolecular hydrophobic interactions. <img src='wiley_img/09359648-2009-21-19-ADMA200803429-content.gif' alt='wiley_img/09359648-2009-21-19-ADMA200803429-content'> </P>
Controlled Array of Ferritin in Tubular Nanostructure
Kim, Min Sup,Shin, Kwang Min,Kim, Sun I.,Spinks, Geoffrey M.,Kim, Seon Jeong WILEY-VCH Verlag 2008 Macromolecular rapid communications Vol.29 No.7
<P>We have demonstrated that uniform and continuous poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (PAMPS) tubular core-shell nanostructures containing linear features of ferritin nanoparticles can be directly fabricated using two immiscible solutions employing coaxial electrospinning. By adjusting the concentration of PAMPS as the outer solution in the coaxial electrospinning process, the width of a one dimensional (1D) array of ferritin could be accurately controlled. We demonstrate the formation of a nearly linear chain of individual ferritin particles encapsulated in a PAMPS nanofiber of 40 nm diameter. The ability to accurately control the width of the ferritin 1D arrays encapsulated in tubular nanostructures is a key component in determining the efficiency and performance of nanodevices. The demonstrated method of forming tubular nanostructures containing inner 1D particle arrays can also be extended to other materials with potential applications in nanoelectronic devices, such as nanobiosensors and batteries.</P><P> <img src='wiley_img/10221336-2008-29-7-MARC200700849-gra001.gif' alt='wiley_img/10221336-2008-29-7-MARC200700849-gra001'> </P>
Switchable redox activity by proton fuelled DNA nano-machines
Shin, Su Ryon,Lee, Chang Kee,Lee, Sun Hee,Kim, Sun I.,Spinks, Geoffrey M.,Wallace, Gordon G.,So, Insuk,Jeong, Ju-Hong,Kang, Tong Mook,Kim, Seon Royal Society of Chemistry 2009 Chemical communications Vol.2009 No.10
<P>The switching electrochemical property of an SWNT/DNA hybrid can be produced through reversible conformational changes between the closed and open state originating from the pH-responding i-motif DNA which significantly improves its molecular switching and stability by hydrophobic interactions with SWNTs.</P> <P>Graphic Abstract</P><P>The switching electrochemical property of an SWNT/DNA hybrid can be produced through reversible conformational changes between the closed and open state originating from the pH-responding i-motif DNA which significantly improves its molecular switching and stability by hydrophobic interactions with SWNTs. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b820634a'> </P>