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Mahadeva, Suresha K,Kim, Jaehwan Elsevier 2011 Science and technology of advanced materials Vol.12 No.5
<P>A highly flexible nanocomposite was developed by coating a regenerated cellulose film with a thin layer of tin oxide (SnO<SUB>2</SUB>) by liquid-phase deposition. Tin oxide was crystallized in solution and formed nanocrystal coatings on regenerated cellulose. The nanocrystalline layers did not exfoliate from cellulose. Transmission electron microscopy and energy dispersive x-ray spectroscopy suggest that SnO<SUB>2</SUB> was not only deposited over the cellulose surface, but also nucleated and grew inside the cellulose film. Current–voltage characteristics of the nanocomposite revealed that its electrical resistivity decreases with deposition time, with the lowest value obtained for 24 h of deposition. The cellulose–SnO<SUB>2</SUB> hybrid nanocomposite can be used for biodegradable and disposable chemical, humidity and biosensors.</P>
Mahadeva, S. K.,Jaehwan Kim IEEE 2013 IEEE SENSORS JOURNAL Vol.13 No.6
<P>This paper investigates the possibility of utilizing tin-oxide (SnO<SUB>2</SUB>)-Coated regenerated cellulose as a disposable and low-cost alternative transducer for urea detection. A thin layer of SnO<SUB>2</SUB> is coated on regenerated cellulose films via liquid-phase deposition technique. Cellulose-SnO<SUB>2</SUB> hybrid nanocomposite urea biosensor is prepared by immobilizing urease on the SnO<SUB>2</SUB> layers by physical absorption method. The resulting biosensor shows a linear response up to 42 mM. Also it is found that the proposed sensor exhibits the same level of sensitivity for seven days; in other words, the sensitivity of the sensor did not degrade with time and remained same for 7 days. This urea sensor is inexpensive, flexible, and disposable.</P>
Mahadeva, Suresha K.,Yi, Chen,Kim, Jae-Hwan The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.2
The cellulose smart material called electro-active paper (EAPap) is made by regenerating cellulose. However, the actuator performance is degraded at low humidity levels. To solve this drawback, EAPap bending actuators were made by activating wet cellulose films in three different room-temperature ionic liquids: l-butyl-3-methylimidazolium hexaflurophosphate ($BMIPF_6$), 1-butyl-3-methylimidazolium chloride (BMICL) and 1-butyl-3-methylimidazolium tetrafluroborate ($BMIBF_4$). In the results, the actuator performance was dependent on the type of anions in the ionic liquids, in the order of $BF_4$>Cl>$PF_6$. The BMIBF 4-activated actuator showed the maximum displacement of 3.8 mm with low electrical power consumption at relatively low humidity. However, the BMICL-activated actuator showed a slight degradation of actuator performance. Further performance and durability improvement will be possible once various ionic liquids are blended with cellulose.
Mahadeva, Suresha K,Kim, Jaehwan Institute of Physics Publishing 2010 Smart materials & structures Vol.19 No.10
<P>This paper reports a cellulose–polypyrrole–ionic liquid (CPIL) nanocomposite that can produce large actuating displacement in a low humidity environment. The fabrication process and actuator performance of the CPIL nanocomposite actuator are illustrated. Experimental results revealed that the size of anion, concentration of ionic liquid and ambient humidity level have a significant influence on the actuator performance of the CPIL nanocomposite. The bending displacement of the CPIL nanocomposite actuator was enhanced with increasing anion size, ionic liquid concentration and humidity level. CPIL nanocomposite made with 4% BMIBF<SUB>4</SUB> ionic liquid exhibited a very large bending displacement with excellent durability under ambient conditions (30% relative humidity and 25 °C). This is probably the first report that cellulose based electro-active paper actuator can exhibit such a large bending displacement under ambient conditions. Experimental results revealed that the proposed CPIL nanocomposite actuator under study can be operated up to 70% humidity level. </P>
Mahadeva, Suresha K.,Kim, Jaehwan,Kang, Kwang Sun,Kim, Heung Soo,Park, Joung Man Wiley Subscription Services, Inc., A Wiley Company 2009 Journal of applied polymer science Vol.114 No.2
<P>This article reports the influence of poly(ethylene oxide)- poly(ethylene glycol) (PEO-PEG) addition on its actuation behavior of cellulose electroactive paper. The actuator showed its maximum bending displacement of 5.0 mm with very low electrical power consumption (7 mW/mm) at an ambient condition. Increased displacement output and decreased electrical power consumption of the actuator might be due to the improved polymer chain flexibility and ion mobility. The ion migration effect might play a more important role in actuation principle. Present investigation reveals that cellulose/PEO-PEG-based EAPap actuators are suitable to construct an actuator working at normal ambient condition. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009</P>
Mahadeva, S.K.,Lee, S.W.,Kim, J. Elsevier Science 2008 Acta materialia Vol.56 No.8
The effect of heat treatment on the structure, piezoelectricity and actuation behavior of cellulose electroactive-paper actuators was studied by infrared spectroscopy, piezoelectricity measurement and the tip displacement test. After heat treatment at 60<SUP>o</SUP>C for 2h, the piezoelectric coefficient (d<SUB>31</SUB>) was enhanced nearly 10-fold as compared to that of non-heat-treated films. However, when the treatment temperature was raised above 60<SUP>o</SUP>C the piezoelectric coefficients were higher than the non-treated film but lower than that of film treated at 60<SUP>o</SUP>C. Infrared and UV-visible spectroscopy suggested that there were changes in chemical structure at higher treatment temperatures. Furthermore, the tip displacement tests performed on the actuators also showed almost same trend as that of the piezoelectric constant.