Jaehwan Kim - Academia.edu (original) (raw)
Papers by Jaehwan Kim
Journal of Applied Physics, 2008
Cellulose based electroactive paper has been developed as smart material. In this paper, corona p... more Cellulose based electroactive paper has been developed as smart material. In this paper, corona poled cellulose films were prepared to improve their piezoelectricity and the influence of grid voltage to the corona poling was investigated. Cellulose was regenerated by dissolving cellulose natural fibers using a solvent, and removing it. During the regeneration process, alignment of cellulose was attempted by applying corona electrical poling. These characteristics were investigated by field emission scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. As increasing the grid voltage of the corona poling, the generation of cellulose nanofibers in the cellulose layered structures was observed, which influenced the increased crystallinity resulting in improved piezoelectric charge constant of cellulose films.
IEEE Sensors Journal, 2000
ABSTRACT We report the fabrication and characterization of a pH sensor made with titanium dioxide... more ABSTRACT We report the fabrication and characterization of a pH sensor made with titanium dioxide (TiO2)/multiwall carbon nanotube (MWCNT)/cellulose hybrid nanocomposite. The TiO2-coated MWCNTs are synthesized by hydrothermal process. The X-ray diffraction and Raman spectra observations show that high anatase crystalline TiO2 nanoparticles are well formed on the surface of MWCNTs. After blending the TiO2/MWCNTs with cellulose solution, the TiO/MWCNT/cellulose hybrid nanocomposite is made and used for the pH sensor. This nanocomposite pH sensor exhibits two linear regions in its conductance between pH 1 and 12. Large surface area of the hybrid nanocomposite increases adsorption sites of ions so as to increase the pH sensitivity as well as sensing range. The long-term stability test and reusable test demonstrate that this hybrid nanocomposite pH sensor is useful for many practical applications. The pH sensing mechanism of this hybrid nanocomposite pH sensor is also discussed in this paper.
IEEE Sensors Journal, 2000
This paper investigates the possibility of utilizing tin-oxide (SnO 2 )-coated regenerated cellul... more This paper investigates the possibility of utilizing tin-oxide (SnO 2 )-coated regenerated cellulose as a disposable and low-cost alternative transducer for urea detection. A thin layer of SnO 2 is coated on regenerated cellulose films via liquid-phase deposition technique. Cellulose-SnO 2 hybrid nanocomposite urea biosensor is prepared by immobilizing urease on the SnO 2 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.
Finite Elements in Analysis and Design, 2006
ABSTRACT Conventional finite element approaches for modeling delaminations in laminated composite... more ABSTRACT Conventional finite element approaches for modeling delaminations in laminated composite structures use the Heaviside unit step function at the interfacial nodes in the delaminated zone of the structure to model the possible jumps in the displacement field during “breathing” of the delaminated layers. In quantum mechanics, the Fermi–Dirac distribution applies to Fermion particles whose characteristics are half-integer spins. The present paper uses the Fermi–Dirac distribution function to model a smoother transition in the displacement and the strain fields of the delaminated interfaces during the opening and closing of the delaminated layers under vibratory loads. This paper successfully shows that the Fermi–Dirac distribution function can be used to more accurately model the dynamic effects of delaminations in laminated composite structures. Optimizing the parameters in the Fermi–Dirac distribution function can lead to more accurate modeling of the dynamic and transient behavior of the delaminated zones in laminated composite structures. This paper also effectively demonstrates how hybrid sensors comprising of out of plane displacement sensors and in plane strain sensors can effectively map a composite structure to detect and locate the delaminated zones. It also shows how simple mode shapes can be used to determine the locations of single and multiple delaminations in laminated composite structures.
Fibers and Polymers, 2012
The regenerated cellulose films were prepared by dissolving cotton cellulose pulp directly in roo... more The regenerated cellulose films were prepared by dissolving cotton cellulose pulp directly in room temperature ionic liquid namely, 1-ethyl-3-methylimidazolium acetate at 80 o C, followed by washing/curing in different coagulants namely, methanol, deionized water, methanol-deionized water, and isopropyl alcohol-deionized water. It was found that the type of coagulants employed for curing the cellulose films has a significant influence on the amount of residual ionic liquid entrapped in the films. The amount of residual ionic liquids was 2.68, 1.01, 0.84, and 0.75 wt.% for the films cured with deionized water, isopropyl alcohol-deionized water, methanol, and methanol-deionized water, respectively. The DTG peaks of regenerated cellulose films showed two decomposition temperatures at 280 o C and 320 o C. Among all the cases studied, deionized water curing case showed the lowest decomposition temperature, attributed to entrapment of large residual ionic liquid in it. Electromechanical characteristic of the regenerated cellulose films was also investigated.
Current Applied Physics, 2012
ABSTRACT
Current Applied Physics, 2011
ABSTRACT
Computer Methods in Applied Mechanics and Engineering, 1996
Scattering of waves involving complex geometries in conjunction with infinite or semi-infinite do... more Scattering of waves involving complex geometries in conjunction with infinite or semi-infinite domains is modeled by introducing a mathematical boundary within which the finite element representation is employed. On the mathematical boundary, the finite element ...
Composites Part B: Engineering, 2012
A hybrid nanocomposite composed of calcium carbonate (CaCO 3 ) and cellulose acetate (CA) was fab... more A hybrid nanocomposite composed of calcium carbonate (CaCO 3 ) and cellulose acetate (CA) was fabricated by bubbling CO 2 gas into the mixture of CA and Ca(OH) 2 solution. Cellulose acetate-calcium carbonate (CA-CC) nanocomposite was characterized by spectral, thermal and optical methods. FTIR and XRD analysis confirmed the formation of the hybrid nanocomposite and XRD confirmed the formation of CaCO 3 with calcite polymorph. Thermal analysis showed CA-CC nanocomposite has better thermal stability than pristine CA. The CaCO 3 nanoparticles were in sphere shape with 100-1000 nm diameter.
Composite Interfaces, 2008
In our early work, cellulose has been discovered as a smart material that can be used as sensors,... more In our early work, cellulose has been discovered as a smart material that can be used as sensors, actuators and smart devices. This newly discovered material is described as electro-active paper (EAPap) and has many advantageous properties: lightweight, flexible, dryness, biodegradable, easy to chemically modify, cheapness and abundance. The actuation principle of cellulose EAPap is based on a combination of
Chinese Science Bulletin, 2009
As a novel piezoelectric material, the mechanical and piezoelectric properties of cellulose elect... more As a novel piezoelectric material, the mechanical and piezoelectric properties of cellulose electro-active paper (EAPap) were studied. Young's modulus of piezoelectric EAPap was dependant on the material orientation as compared with other EAP materials. The highest Young's modulus was obtained at 0° direction, while the highest direct piezoelectric charge constant was achieved at 45°. By measuring the induced output voltage from the thin piezoelectric cellulose film under the applied impact force, we demonstrate that piezoelectric EAPap film has a potential for sensor applications.
Cellulose, 2010
Bacterial cellulose (BC)/poly(ethylene glycol) (PEG) composite was prepared by immersing wet BC p... more Bacterial cellulose (BC)/poly(ethylene glycol) (PEG) composite was prepared by immersing wet BC pellicle in PEG aqueous solution followed by freeze-drying process. The product looks like a foam structure. The morphology of BC/PEG composite was examined by scanning electron microscope (SEM) and compared with pristine BC. SEM images showed that PEG molecules was not only coated on the BC fibrils surface
Cellulose, 2011
Zinc oxide (ZnO) nanoparticles were immobilized on the surface of regenerated cellulose films by ... more Zinc oxide (ZnO) nanoparticles were immobilized on the surface of regenerated cellulose films by a wet chemical method in which the controlled hydrolysis of a Zn(II)-amine complex leads to the formation of ZnO nanoparticles. Cellulose-ZnO materials were characterized by spectral, thermal and optical methods. Scanning electron microscope and atomic force microscope analyses confirmed the formation of ZnO nanoparticles on the surface of the regenerated cellulose film and X-ray diffraction patterns showed the ZnO had the wurtzite structure. The reported method is very simple, and can immobilize the nanoparticles without the aid of a binder or dendritic side group and without high temperature treatments like calcination. ZnO immobilized on biopolymers like cellulose has many potential applications such as strain sensors, biomedical sensors, flexible display devices and optoelectronics.
Cellulose, 2010
Page 1. Preparation and characterization of bacterial cellulose membranes with tailored surface a... more Page 1. Preparation and characterization of bacterial cellulose membranes with tailored surface and barrier properties Liliana C. Tomé Lúcia Brandao Adélio M. Mendes Armando JD Silvestre Carlos Pascoal Neto Alessandro ...
Applied Physics Letters, 2009
We report a flexible paper transistor made with regenerated cellulose and covalently bonded multi... more We report a flexible paper transistor made with regenerated cellulose and covalently bonded multiwalled carbon nanotube ͑RC-MWCNT͒. MWCNT bonded to cellulose chains can act as electron channel paths in dielectric cellulose layers. It is found that the covalent bonding between cellulose and MWCNT can be modulated by reaction time and temperature. The RC-MWCNT paper transistor shows that the leakage current and the on/off ratio are strongly associated with the concentration of MWCNTs. The estimated electron mobility of RC-MWCNT paper is comparable to other organic transistor materials. The RC-MWCNT paper transistor has a potential for flexible electronic paper.
![Research paper thumbnail of The effect of TiO[sub 2] nanoparticle concentration on conduction mechanism for TiO[sub 2]-polymer diode](https://attachments.academia-assets.com/65865035/thumbnails/1.jpg)
](Applied Physics Letters, 2008
The plots of ͑a͒ ln͑J͒ vs E 1/2 , ͑b͒ ln͑J / V͒ vs E 1/2 , and ͑c͒ ln͑J͒ vs ln͑V͒ representing Sc... more The plots of ͑a͒ ln͑J͒ vs E 1/2 , ͑b͒ ln͑J / V͒ vs E 1/2 , and ͑c͒ ln͑J͒ vs ln͑V͒ representing Schottky, Poole-Frenkel, and SCLC mechanism.
Entire Site, Smart Structures and Materials 2006: Smart Electronics, MEMS, BioMEMS, and Nanotechn... more Entire Site, Smart Structures and Materials 2006: Smart Electronics, MEMS, BioMEMS, and Nanotechnology (Proceedings Volume). ...
Proceedings of SPIE, 1999
Modeling of piezoelectric smart structures including absorbing material was studied for cabin noi... more Modeling of piezoelectric smart structures including absorbing material was studied for cabin noise problems. The finite element method which uses a combination of three dimensional piezoelectric, flat shell and transition finite elements is adopted to model the piezoelectric ...
AIAA Journal, 2007
ABSTRACT
Journal of Applied Physics, 2008
Cellulose based electroactive paper has been developed as smart material. In this paper, corona p... more Cellulose based electroactive paper has been developed as smart material. In this paper, corona poled cellulose films were prepared to improve their piezoelectricity and the influence of grid voltage to the corona poling was investigated. Cellulose was regenerated by dissolving cellulose natural fibers using a solvent, and removing it. During the regeneration process, alignment of cellulose was attempted by applying corona electrical poling. These characteristics were investigated by field emission scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. As increasing the grid voltage of the corona poling, the generation of cellulose nanofibers in the cellulose layered structures was observed, which influenced the increased crystallinity resulting in improved piezoelectric charge constant of cellulose films.
IEEE Sensors Journal, 2000
ABSTRACT We report the fabrication and characterization of a pH sensor made with titanium dioxide... more ABSTRACT We report the fabrication and characterization of a pH sensor made with titanium dioxide (TiO2)/multiwall carbon nanotube (MWCNT)/cellulose hybrid nanocomposite. The TiO2-coated MWCNTs are synthesized by hydrothermal process. The X-ray diffraction and Raman spectra observations show that high anatase crystalline TiO2 nanoparticles are well formed on the surface of MWCNTs. After blending the TiO2/MWCNTs with cellulose solution, the TiO/MWCNT/cellulose hybrid nanocomposite is made and used for the pH sensor. This nanocomposite pH sensor exhibits two linear regions in its conductance between pH 1 and 12. Large surface area of the hybrid nanocomposite increases adsorption sites of ions so as to increase the pH sensitivity as well as sensing range. The long-term stability test and reusable test demonstrate that this hybrid nanocomposite pH sensor is useful for many practical applications. The pH sensing mechanism of this hybrid nanocomposite pH sensor is also discussed in this paper.
IEEE Sensors Journal, 2000
This paper investigates the possibility of utilizing tin-oxide (SnO 2 )-coated regenerated cellul... more This paper investigates the possibility of utilizing tin-oxide (SnO 2 )-coated regenerated cellulose as a disposable and low-cost alternative transducer for urea detection. A thin layer of SnO 2 is coated on regenerated cellulose films via liquid-phase deposition technique. Cellulose-SnO 2 hybrid nanocomposite urea biosensor is prepared by immobilizing urease on the SnO 2 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.
Finite Elements in Analysis and Design, 2006
ABSTRACT Conventional finite element approaches for modeling delaminations in laminated composite... more ABSTRACT Conventional finite element approaches for modeling delaminations in laminated composite structures use the Heaviside unit step function at the interfacial nodes in the delaminated zone of the structure to model the possible jumps in the displacement field during “breathing” of the delaminated layers. In quantum mechanics, the Fermi–Dirac distribution applies to Fermion particles whose characteristics are half-integer spins. The present paper uses the Fermi–Dirac distribution function to model a smoother transition in the displacement and the strain fields of the delaminated interfaces during the opening and closing of the delaminated layers under vibratory loads. This paper successfully shows that the Fermi–Dirac distribution function can be used to more accurately model the dynamic effects of delaminations in laminated composite structures. Optimizing the parameters in the Fermi–Dirac distribution function can lead to more accurate modeling of the dynamic and transient behavior of the delaminated zones in laminated composite structures. This paper also effectively demonstrates how hybrid sensors comprising of out of plane displacement sensors and in plane strain sensors can effectively map a composite structure to detect and locate the delaminated zones. It also shows how simple mode shapes can be used to determine the locations of single and multiple delaminations in laminated composite structures.
Fibers and Polymers, 2012
The regenerated cellulose films were prepared by dissolving cotton cellulose pulp directly in roo... more The regenerated cellulose films were prepared by dissolving cotton cellulose pulp directly in room temperature ionic liquid namely, 1-ethyl-3-methylimidazolium acetate at 80 o C, followed by washing/curing in different coagulants namely, methanol, deionized water, methanol-deionized water, and isopropyl alcohol-deionized water. It was found that the type of coagulants employed for curing the cellulose films has a significant influence on the amount of residual ionic liquid entrapped in the films. The amount of residual ionic liquids was 2.68, 1.01, 0.84, and 0.75 wt.% for the films cured with deionized water, isopropyl alcohol-deionized water, methanol, and methanol-deionized water, respectively. The DTG peaks of regenerated cellulose films showed two decomposition temperatures at 280 o C and 320 o C. Among all the cases studied, deionized water curing case showed the lowest decomposition temperature, attributed to entrapment of large residual ionic liquid in it. Electromechanical characteristic of the regenerated cellulose films was also investigated.
Current Applied Physics, 2012
ABSTRACT
Current Applied Physics, 2011
ABSTRACT
Computer Methods in Applied Mechanics and Engineering, 1996
Scattering of waves involving complex geometries in conjunction with infinite or semi-infinite do... more Scattering of waves involving complex geometries in conjunction with infinite or semi-infinite domains is modeled by introducing a mathematical boundary within which the finite element representation is employed. On the mathematical boundary, the finite element ...
Composites Part B: Engineering, 2012
A hybrid nanocomposite composed of calcium carbonate (CaCO 3 ) and cellulose acetate (CA) was fab... more A hybrid nanocomposite composed of calcium carbonate (CaCO 3 ) and cellulose acetate (CA) was fabricated by bubbling CO 2 gas into the mixture of CA and Ca(OH) 2 solution. Cellulose acetate-calcium carbonate (CA-CC) nanocomposite was characterized by spectral, thermal and optical methods. FTIR and XRD analysis confirmed the formation of the hybrid nanocomposite and XRD confirmed the formation of CaCO 3 with calcite polymorph. Thermal analysis showed CA-CC nanocomposite has better thermal stability than pristine CA. The CaCO 3 nanoparticles were in sphere shape with 100-1000 nm diameter.
Composite Interfaces, 2008
In our early work, cellulose has been discovered as a smart material that can be used as sensors,... more In our early work, cellulose has been discovered as a smart material that can be used as sensors, actuators and smart devices. This newly discovered material is described as electro-active paper (EAPap) and has many advantageous properties: lightweight, flexible, dryness, biodegradable, easy to chemically modify, cheapness and abundance. The actuation principle of cellulose EAPap is based on a combination of
Chinese Science Bulletin, 2009
As a novel piezoelectric material, the mechanical and piezoelectric properties of cellulose elect... more As a novel piezoelectric material, the mechanical and piezoelectric properties of cellulose electro-active paper (EAPap) were studied. Young's modulus of piezoelectric EAPap was dependant on the material orientation as compared with other EAP materials. The highest Young's modulus was obtained at 0° direction, while the highest direct piezoelectric charge constant was achieved at 45°. By measuring the induced output voltage from the thin piezoelectric cellulose film under the applied impact force, we demonstrate that piezoelectric EAPap film has a potential for sensor applications.
Cellulose, 2010
Bacterial cellulose (BC)/poly(ethylene glycol) (PEG) composite was prepared by immersing wet BC p... more Bacterial cellulose (BC)/poly(ethylene glycol) (PEG) composite was prepared by immersing wet BC pellicle in PEG aqueous solution followed by freeze-drying process. The product looks like a foam structure. The morphology of BC/PEG composite was examined by scanning electron microscope (SEM) and compared with pristine BC. SEM images showed that PEG molecules was not only coated on the BC fibrils surface
Cellulose, 2011
Zinc oxide (ZnO) nanoparticles were immobilized on the surface of regenerated cellulose films by ... more Zinc oxide (ZnO) nanoparticles were immobilized on the surface of regenerated cellulose films by a wet chemical method in which the controlled hydrolysis of a Zn(II)-amine complex leads to the formation of ZnO nanoparticles. Cellulose-ZnO materials were characterized by spectral, thermal and optical methods. Scanning electron microscope and atomic force microscope analyses confirmed the formation of ZnO nanoparticles on the surface of the regenerated cellulose film and X-ray diffraction patterns showed the ZnO had the wurtzite structure. The reported method is very simple, and can immobilize the nanoparticles without the aid of a binder or dendritic side group and without high temperature treatments like calcination. ZnO immobilized on biopolymers like cellulose has many potential applications such as strain sensors, biomedical sensors, flexible display devices and optoelectronics.
Cellulose, 2010
Page 1. Preparation and characterization of bacterial cellulose membranes with tailored surface a... more Page 1. Preparation and characterization of bacterial cellulose membranes with tailored surface and barrier properties Liliana C. Tomé Lúcia Brandao Adélio M. Mendes Armando JD Silvestre Carlos Pascoal Neto Alessandro ...
Applied Physics Letters, 2009
We report a flexible paper transistor made with regenerated cellulose and covalently bonded multi... more We report a flexible paper transistor made with regenerated cellulose and covalently bonded multiwalled carbon nanotube ͑RC-MWCNT͒. MWCNT bonded to cellulose chains can act as electron channel paths in dielectric cellulose layers. It is found that the covalent bonding between cellulose and MWCNT can be modulated by reaction time and temperature. The RC-MWCNT paper transistor shows that the leakage current and the on/off ratio are strongly associated with the concentration of MWCNTs. The estimated electron mobility of RC-MWCNT paper is comparable to other organic transistor materials. The RC-MWCNT paper transistor has a potential for flexible electronic paper.
Applied Physics Letters, 2008
The plots of ͑a͒ ln͑J͒ vs E 1/2 , ͑b͒ ln͑J / V͒ vs E 1/2 , and ͑c͒ ln͑J͒ vs ln͑V͒ representing Sc... more The plots of ͑a͒ ln͑J͒ vs E 1/2 , ͑b͒ ln͑J / V͒ vs E 1/2 , and ͑c͒ ln͑J͒ vs ln͑V͒ representing Schottky, Poole-Frenkel, and SCLC mechanism.
Entire Site, Smart Structures and Materials 2006: Smart Electronics, MEMS, BioMEMS, and Nanotechn... more Entire Site, Smart Structures and Materials 2006: Smart Electronics, MEMS, BioMEMS, and Nanotechnology (Proceedings Volume). ...
Proceedings of SPIE, 1999
Modeling of piezoelectric smart structures including absorbing material was studied for cabin noi... more Modeling of piezoelectric smart structures including absorbing material was studied for cabin noise problems. The finite element method which uses a combination of three dimensional piezoelectric, flat shell and transition finite elements is adopted to model the piezoelectric ...
AIAA Journal, 2007
ABSTRACT