Carbon and boron have been considered to strengthen grain boundaries that might form during single crystal casting.In this study the effect of boron on solidification behavior and creep properties of the carbon doped ...Carbon and boron have been considered to strengthen grain boundaries that might form during single crystal casting.In this study the effect of boron on solidification behavior and creep properties of the carbon doped single crystal RR 2072 has been investigated.In order to understand solidification behavior with boron addition,the solid/liquid interface morphology and solidification microstructure were examined with solidification rate.The relationship between mi-crostructural evolution and creep properties of the carbon and boron modified single crystal has been also investigated.展开更多
This paper deals with a series of novel processing techniques based on the in situ production of metal matrix composites (MMCs). In situ techniques involve a chemical reaction resulting in the formation of a very fine...This paper deals with a series of novel processing techniques based on the in situ production of metal matrix composites (MMCs). In situ techniques involve a chemical reaction resulting in the formation of a very fine and thermodynamically stable reinforcing ceramic phase within a metal matrix. As a result, this provides thermodynamic compatibility at the matrix-reinforcement interface. The reinforcement surfaces are also likely to be free of contamination and, therefore, a stronger matrix-dispersion bond can be achieved. Some of these technologies including DIMOX^? XD, PRIMEX^? reactive gas infiltration, high-temperature self-propagating synthesis (SHS), and liquid-solid, or solid-gas-liquid reactions as well as plasma in situ MMCs are expressed in this paper.展开更多
The Bi-2223/Ag tapes were prepared with spray-died powders, which are of different particle sizes and phase assemblages by varying the annealing time in pure oxygen. Longer time annealing degraded the reactivity of pr...The Bi-2223/Ag tapes were prepared with spray-died powders, which are of different particle sizes and phase assemblages by varying the annealing time in pure oxygen. Longer time annealing degraded the reactivity of precursor powder, which in turn resulted in an incomplete conversion from precursors to Bi-2223, porosity core and misaligned grains in fully processed tapes. The best Jc in short pressed samples varied from 29.7 to 47kA/cm2 for the tapes made from different powders.展开更多
Understanding the mechanical properties of bionanofilms is important in terms of identifying their durability.The primary focus of this study is to examine the effect of water vapor annealed silk fibroin on the indent...Understanding the mechanical properties of bionanofilms is important in terms of identifying their durability.The primary focus of this study is to examine the effect of water vapor annealed silk fibroin on the indentation modulus and hardness of graphene oxide-silk fibroin(GO-SF)bionanofilms through nanoindentation experiments and finite element analysis(FEA).The GO-SF bionanofilms were fabricated using the layer-by-layer technique.The water vapor annealing process was employed to enhance the interfacial properties between the GO and SF layers,and the mechanical properties of the GO-SF bionanofilms were found to be affected by this process.By employing water vapor annealing,the indentation modulus and hardness of the GO-SF bionanofilms can be improved.Furthermore,the FEA models of the GO-SF bionanofilms were developed to simulate the details of the mechanical behaviors of the GO-SF bionanofilms.The difference in the stress and strain distribution inside the GO-SF bionanofilms before and after annealing was analyzed.In addition,the load-displacement curves that were obtained by the developed FEA model conformed well with the results from the nanoindentation tests.In summary,this study presents the mechanism of improving the indentation modulus and hardness of the GO-SF bionanofilms through the water vapor annealing process,which is established with the FEA simulation models.展开更多
The soft robot manipulator is attracting attention in the surgical fields with its intrinsic softness,lightness in its weight,and safety toward the human organ.However,it cannot be used widely because of its difficult...The soft robot manipulator is attracting attention in the surgical fields with its intrinsic softness,lightness in its weight,and safety toward the human organ.However,it cannot be used widely because of its difficulty of control.To control a soft robot manipulator accurately,shape sensing is essential.This paper presents a method of estimating the shape of a soft robot manipulator by using a skin-type stretchable sensor composed of a multiwalled carbon nanotube(MWCNT)and silicone(p7670).The sensor can be easily fabricated and applied by simply attaching it to the surface of the soft manipulator.In its fabrication,MWCNT is sprayed on a teflon sheet,and liquid-state silicone is poured on it.After curing,we turn it over and cover it with another silicone layer.The sensor is fabricated with a sandwich structure to decrease the hysteresis of the sensor.After calibration and determining the relationship between the resistance of the sensor and the strain,three sensors are attached at 120°intervals.Using the obtained data,the curvature of the manipulator is calculated,and the entire shape is reconstructed.To validate its accuracy,the estimated shape is compared with the camera data.We experiment with three,six,and nine sensors attached,and the result of the error of shape estimation is compared.As a result,the minimum tip position error is approximately 8.9 mm,which corresponded to 4.45%of the total length of the manipulator when using nine sensors.展开更多
The demand for multifunctional neural interfaces has grown due to the need to provide a better understanding of biological mechanisms related to neurological diseases and neural networks.Direct intracerebral drug inje...The demand for multifunctional neural interfaces has grown due to the need to provide a better understanding of biological mechanisms related to neurological diseases and neural networks.Direct intracerebral drug injection using microfluidic neural interfaces is an effective way to deliver drugs to the brain,and it expands the utility of drugs by bypassing the blood-brain barrier(BBB).In addition,uses of implantable neural interfacing devices have been challenging due to inevitable acute and chronic tissue responses around the electrodes,pointing to a critical issue still to be overcome.Although neural interfaces comprised of a collection of microneedles in an array have been used for various applications,it has been challenging to integrate microfluidic channels with them due to their characteristic three-dimensional structures,which differ from two-dimensionally fabricated shank-type neural probes.Here we present a method to provide such three-dimensional needle-type arrays with chemical delivery functionality.We fabricated a microfluidic interconnection cable(pFIC)and integrated it with a flexible penetrating microelectrode array(FPMA)that has a 3-dimensional structure comprised of silicon microneedle electrodes supported by a flexible array base.We successfully demonstrated chemical delivery through the developed device by recording neural signals acutely from in vivo brains before and after KCl injection.This suggests the potential of the developed microfluidic neural interface to contribute to neuroscience research by providing simultaneous signal recording and chemical delivery capabilities.展开更多
The recent advances of wearable sensors are remarkable but there are still limitations that they need to be refabricated to tune the sensor for target signal.However,biological sensory systems have the inherent potent...The recent advances of wearable sensors are remarkable but there are still limitations that they need to be refabricated to tune the sensor for target signal.However,biological sensory systems have the inherent potential to adjust their sensitivity according to the external environment,allowing for a broad and enhanced detection.Here,we developed a Tunable,Ultrasensitive,Nature-inspired,Epidermal Sensor(TUNES)that the strain sensitivity was dramatically increased(GF~30k)and the pressure sensitivity could be tuned(10–254 kPa^(−1))by preset membrane tension.The sensor adjusts the sensitivity to the pressure regime by preset tension,so it can measure a wide range(0.05 Pa–25 kPa)with the best performance:from very small signals such as minute pulse to relatively large signals such as muscle contraction and respiration.We verified its capabilities as a wearable health monitoring system by clinical trial comparing with pressure wire which is considered the current gold standard of blood pressure(r=0.96)and home health care system by binary classification of Old’s/Young’s pulse waves via machine learning(accuracy 95%).展开更多
Bioresponsive hydrogels are smart materials that respond to various external stimuli and exhibit great potential as biosensors owing to their capability of real-time and label-free detection.Here,we propose a sensing ...Bioresponsive hydrogels are smart materials that respond to various external stimuli and exhibit great potential as biosensors owing to their capability of real-time and label-free detection.Here,we propose a sensing platform based on bioresponsive hydrogels,employing the concept of moiré patterns.Two sets of line patterns with different pitch sizes are prepared;a hydrogel grating whose pitch size changes according to external stimuli and a reference grating with constant pitch size.The volume changes of the hydrogel caused by external stimuli changes the pitch size of the hydrogel grating,and subsequently,the pitch sizes of the moiré patterns(moiré signal),whose values can be obtained in a real-time and label-free manner through customized moiré microscopy and signal processing.After confirming that the pH-induced swelling of hydrogel could be monitored using moiré patterns,we performed moiré pattern-based detection of specific proteins using protein-responsive hydrogel that underwent shrinking via interaction with target proteins.Brain-derived neurotrophic factor and platelet-derived growth factor were selected as the model proteins,and our proposed system successfully detected both proteins at nanomolar levels.In both cases,the pitch size change of hydrogel grating was monitored much more sensitively using moiré patterns than through direct measurements.The changes in the moiré signals caused by target proteins were detected in ex-vivo environments using a custom-made intraocular lens incorporating the hydrogel grating,demonstrating the capability of the proposed system to detect various markers in intraocular aqueous humor,when implanted in the eye.展开更多
A flexible full-color micro-LED display with high mechanical robustness was fabricated by printing quantum dots(QDs)on a blue micro-LED array using standard photolithography.The red and green colors yielded from QDs e...A flexible full-color micro-LED display with high mechanical robustness was fabricated by printing quantum dots(QDs)on a blue micro-LED array using standard photolithography.The red and green colors yielded from QDs exhibit a better color gamut than conventional color filters.The light conversion efficiency was enhanced by adding TiO2 nanoparticles to the QD-photoresist composite.This full-color micro-LED display was successfully mounted on various unusual substrates such as curved glass,fabrics,and human skin,enabling diverse optoelectronic applications.In addition,wireless multi-channel visible light communication(VLC)based on the wavelength-division-multiplexing orthogonal-frequency-division-multiplexing(WDM-OFDM)technique was demonstrated using a QD-based color micro-LED panel.A high data transmission rate of 1.9 Gbps was successfully obtained owing to the high electrical-optical modulation bandwidth of the QD-based micro-LED panel.展开更多
文摘Carbon and boron have been considered to strengthen grain boundaries that might form during single crystal casting.In this study the effect of boron on solidification behavior and creep properties of the carbon doped single crystal RR 2072 has been investigated.In order to understand solidification behavior with boron addition,the solid/liquid interface morphology and solidification microstructure were examined with solidification rate.The relationship between mi-crostructural evolution and creep properties of the carbon and boron modified single crystal has been also investigated.
文摘This paper deals with a series of novel processing techniques based on the in situ production of metal matrix composites (MMCs). In situ techniques involve a chemical reaction resulting in the formation of a very fine and thermodynamically stable reinforcing ceramic phase within a metal matrix. As a result, this provides thermodynamic compatibility at the matrix-reinforcement interface. The reinforcement surfaces are also likely to be free of contamination and, therefore, a stronger matrix-dispersion bond can be achieved. Some of these technologies including DIMOX^? XD, PRIMEX^? reactive gas infiltration, high-temperature self-propagating synthesis (SHS), and liquid-solid, or solid-gas-liquid reactions as well as plasma in situ MMCs are expressed in this paper.
文摘The Bi-2223/Ag tapes were prepared with spray-died powders, which are of different particle sizes and phase assemblages by varying the annealing time in pure oxygen. Longer time annealing degraded the reactivity of precursor powder, which in turn resulted in an incomplete conversion from precursors to Bi-2223, porosity core and misaligned grains in fully processed tapes. The best Jc in short pressed samples varied from 29.7 to 47kA/cm2 for the tapes made from different powders.
基金This work was supported by the National Research Foundation of Korea(NRF)grant that was funded by the Korea Government(MSIT)(No.NRF-2018R1C1B6002339).
文摘Understanding the mechanical properties of bionanofilms is important in terms of identifying their durability.The primary focus of this study is to examine the effect of water vapor annealed silk fibroin on the indentation modulus and hardness of graphene oxide-silk fibroin(GO-SF)bionanofilms through nanoindentation experiments and finite element analysis(FEA).The GO-SF bionanofilms were fabricated using the layer-by-layer technique.The water vapor annealing process was employed to enhance the interfacial properties between the GO and SF layers,and the mechanical properties of the GO-SF bionanofilms were found to be affected by this process.By employing water vapor annealing,the indentation modulus and hardness of the GO-SF bionanofilms can be improved.Furthermore,the FEA models of the GO-SF bionanofilms were developed to simulate the details of the mechanical behaviors of the GO-SF bionanofilms.The difference in the stress and strain distribution inside the GO-SF bionanofilms before and after annealing was analyzed.In addition,the load-displacement curves that were obtained by the developed FEA model conformed well with the results from the nanoindentation tests.In summary,this study presents the mechanism of improving the indentation modulus and hardness of the GO-SF bionanofilms through the water vapor annealing process,which is established with the FEA simulation models.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2020R1A4A1018227).
文摘The soft robot manipulator is attracting attention in the surgical fields with its intrinsic softness,lightness in its weight,and safety toward the human organ.However,it cannot be used widely because of its difficulty of control.To control a soft robot manipulator accurately,shape sensing is essential.This paper presents a method of estimating the shape of a soft robot manipulator by using a skin-type stretchable sensor composed of a multiwalled carbon nanotube(MWCNT)and silicone(p7670).The sensor can be easily fabricated and applied by simply attaching it to the surface of the soft manipulator.In its fabrication,MWCNT is sprayed on a teflon sheet,and liquid-state silicone is poured on it.After curing,we turn it over and cover it with another silicone layer.The sensor is fabricated with a sandwich structure to decrease the hysteresis of the sensor.After calibration and determining the relationship between the resistance of the sensor and the strain,three sensors are attached at 120°intervals.Using the obtained data,the curvature of the manipulator is calculated,and the entire shape is reconstructed.To validate its accuracy,the estimated shape is compared with the camera data.We experiment with three,six,and nine sensors attached,and the result of the error of shape estimation is compared.As a result,the minimum tip position error is approximately 8.9 mm,which corresponded to 4.45%of the total length of the manipulator when using nine sensors.
基金supported by the Brain Research Program under Grant No.NRF-2018M3C7A1022309 through the National Research Foundation of Korea.
文摘The demand for multifunctional neural interfaces has grown due to the need to provide a better understanding of biological mechanisms related to neurological diseases and neural networks.Direct intracerebral drug injection using microfluidic neural interfaces is an effective way to deliver drugs to the brain,and it expands the utility of drugs by bypassing the blood-brain barrier(BBB).In addition,uses of implantable neural interfacing devices have been challenging due to inevitable acute and chronic tissue responses around the electrodes,pointing to a critical issue still to be overcome.Although neural interfaces comprised of a collection of microneedles in an array have been used for various applications,it has been challenging to integrate microfluidic channels with them due to their characteristic three-dimensional structures,which differ from two-dimensionally fabricated shank-type neural probes.Here we present a method to provide such three-dimensional needle-type arrays with chemical delivery functionality.We fabricated a microfluidic interconnection cable(pFIC)and integrated it with a flexible penetrating microelectrode array(FPMA)that has a 3-dimensional structure comprised of silicon microneedle electrodes supported by a flexible array base.We successfully demonstrated chemical delivery through the developed device by recording neural signals acutely from in vivo brains before and after KCl injection.This suggests the potential of the developed microfluidic neural interface to contribute to neuroscience research by providing simultaneous signal recording and chemical delivery capabilities.
基金supported by funding from NRF of Korea(grant no.2019R1H1A1080221,2019R1F1A1063066,2019R1C1C1007629,2021R1A6A3A01087289,2021R1A6A3A13045869,2022R1A2C2093100,2022R1A6A3A13071489)supported by Korea Environment Industry&Technology Institute(KEITI)through Digital Infrastructure Building Project for Monitoring,Surveying,and Evaluating the Environmental Health Program,funded by Korea Ministry of Environment(MOE)(2021003330009)supported by a grant of the Basic Research Program funded by the Korea Institute of Machinery and Materials(grant number:NK231A).
文摘The recent advances of wearable sensors are remarkable but there are still limitations that they need to be refabricated to tune the sensor for target signal.However,biological sensory systems have the inherent potential to adjust their sensitivity according to the external environment,allowing for a broad and enhanced detection.Here,we developed a Tunable,Ultrasensitive,Nature-inspired,Epidermal Sensor(TUNES)that the strain sensitivity was dramatically increased(GF~30k)and the pressure sensitivity could be tuned(10–254 kPa^(−1))by preset membrane tension.The sensor adjusts the sensitivity to the pressure regime by preset tension,so it can measure a wide range(0.05 Pa–25 kPa)with the best performance:from very small signals such as minute pulse to relatively large signals such as muscle contraction and respiration.We verified its capabilities as a wearable health monitoring system by clinical trial comparing with pressure wire which is considered the current gold standard of blood pressure(r=0.96)and home health care system by binary classification of Old’s/Young’s pulse waves via machine learning(accuracy 95%).
基金This work was supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(Ministry of Science and ICT)(NRF-2017M3A7B4041798,NRF-2021R1A2C4001596,and NRF-2017M3D1A1039289).
文摘Bioresponsive hydrogels are smart materials that respond to various external stimuli and exhibit great potential as biosensors owing to their capability of real-time and label-free detection.Here,we propose a sensing platform based on bioresponsive hydrogels,employing the concept of moiré patterns.Two sets of line patterns with different pitch sizes are prepared;a hydrogel grating whose pitch size changes according to external stimuli and a reference grating with constant pitch size.The volume changes of the hydrogel caused by external stimuli changes the pitch size of the hydrogel grating,and subsequently,the pitch sizes of the moiré patterns(moiré signal),whose values can be obtained in a real-time and label-free manner through customized moiré microscopy and signal processing.After confirming that the pH-induced swelling of hydrogel could be monitored using moiré patterns,we performed moiré pattern-based detection of specific proteins using protein-responsive hydrogel that underwent shrinking via interaction with target proteins.Brain-derived neurotrophic factor and platelet-derived growth factor were selected as the model proteins,and our proposed system successfully detected both proteins at nanomolar levels.In both cases,the pitch size change of hydrogel grating was monitored much more sensitively using moiré patterns than through direct measurements.The changes in the moiré signals caused by target proteins were detected in ex-vivo environments using a custom-made intraocular lens incorporating the hydrogel grating,demonstrating the capability of the proposed system to detect various markers in intraocular aqueous humor,when implanted in the eye.
基金supported by the National Research Foundation of Korea (NRF) funded by the Korean government (MSIT) (NRF-2015R1A3A2066337)the Research Program of Korea Institute of Machinery&Materials (NK230D).
文摘A flexible full-color micro-LED display with high mechanical robustness was fabricated by printing quantum dots(QDs)on a blue micro-LED array using standard photolithography.The red and green colors yielded from QDs exhibit a better color gamut than conventional color filters.The light conversion efficiency was enhanced by adding TiO2 nanoparticles to the QD-photoresist composite.This full-color micro-LED display was successfully mounted on various unusual substrates such as curved glass,fabrics,and human skin,enabling diverse optoelectronic applications.In addition,wireless multi-channel visible light communication(VLC)based on the wavelength-division-multiplexing orthogonal-frequency-division-multiplexing(WDM-OFDM)technique was demonstrated using a QD-based color micro-LED panel.A high data transmission rate of 1.9 Gbps was successfully obtained owing to the high electrical-optical modulation bandwidth of the QD-based micro-LED panel.
