The Experts below are selected from a list of 40419 Experts worldwide ranked by ideXlab platform
Shizhi Qian - One of the best experts on this subject based on the ideXlab platform.
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Gate manipulation of ionic conductance in a nanochannel with overlapped electric double layers
Sensors and Actuators B-chemical, 2015Co-Authors: Li-hsien Yeh, Song Xue, Shizhi QianAbstract:Abstract To improve the development of Gated nanofluidic devices for emerging applications, analytical expressions are derived to investiGate the Gate manipulation of surface charge property and ionic conductance in a pH-regulated nanochannel with overlapped electric double layers (EDLs). Results show that the EDL overlap effect is relatively significant at low pH and salt concentration when a negative Gate Potential is applied. If pH is low, the EDL overlap effect on the field control of zeta Potential of the nanochannel is remarkable at large positive Gate voltage, while that effect on ionic conductance is significant at large negative Gate voltage.
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field effect modulation of surface charge property and electroosmotic flow in a nanochannel stern layer effect
Journal of Physical Chemistry C, 2013Co-Authors: Christopher Hughes, Li-hsien Yeh, Shizhi QianAbstract:Active control of surface charge property and electroosmotic flow (EOF) in a silica-based nanochannel using a field effect transistor (FET) is analyzed for the first time taking the Stern layer effect into account. Approximations for surface charge property and EOF have been derived and validated by comparing their predictions with experimental data available in the literature. We show that, in addition to the background solution properties such as its pH and salt concentration, the field effect control of the zeta Potential of the nanochannel wall and the EOF velocity depends highly on the surface capacitance of the Stern layer, stemming from the attraction of immobile counterions within that layer. The Stern layer effect becomes significant when the background salt concentration, solution pH, and/or the applied Gate Potential are relatively high. Results gathered provide valuable information for designing relevant Gated nanofluidic devices for regulating ion, fluid flow, and biomolecule transport.
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Field effect regulation of Donnan Potential and electrokinetic flow in a functionalized soft nanochannel
Soft Matter, 2013Co-Authors: Laura Benson, Tzung-han Chou, Li-hsien Yeh, Shizhi QianAbstract:Controlling charge properties and electrokinetic flow (EKF) in a nanochannel is essential for the development of next generation nanofluidics based biosensing devices. In this study, active control of the Donnan Potential and EKF in a functionalized soft nanochannel, comprising a solid-state nanochannel functionalized with a polyelectrolyte (PE) brush layer, using a field effect transistor (FET) is theoretically investiGated for the first time. Both the magnitude and sign of the Donnan Potential in the functionalized soft nanochannel can be effectively regulated by the Gate Potential imposed on the FET and the salt concentration. In addition, the salt concentration dependence of the EKF velocity profiles inside and outside the PE brush layer of the functionalized soft nanochannel are distinctly different.
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field effect control of electrokinetic transport in micro nanofluidics
Sensors and Actuators B-chemical, 2012Co-Authors: Shizhi QianAbstract:Abstract Electrokinetics has emerged as one of the most promising techniques to transport and manipulate ions, fluid and particles in micro/nanofluidic devices. Field effect permits flexible and rapid control of the surface charge property on the channel wall, which in turn offers a more sophisticated control of the electrokinetic transport phenomena in micro/nanofluidics. In the field effect control, a Potential named as Gate Potential is applied to a Gate electrode patterned on the outer surface of the dielectric channel wall in contact with an aqueous solution, and the imposed radial electric field can effectively modulate the surface Potential at the channel/liquid interface, resulting in the redistribution of ions and accordingly the ionic conductance of a nanochannel. The modulation of the surface Potential at the channel/liquid interface can also affect the electrokinetic transport of fluids and particles. This tutorial review elucidates the physical mechanism and discusses some typical results of the field effect control of ion, fluid and particle electrokinetic transport in micro/nanofluidics.
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ionic current rectification in a conical nanofluidic field effect transistor
Sensors and Actuators B-chemical, 2011Co-Authors: Jing Liu, Shizhi Qian, Bingkai ZhangAbstract:Abstract A conical nanofluidic field effect transistor (FET) refers to a conical nanopore embedded with an electrically controllable Gate electrode. The surface Potential of the nanopore can be effectively regulated by manipulating the Gate Potential applied to the Gate electrode, which in turn controls the ionic current through the nanopore. The field effect on the ionic current rectification (ICR) in the conical nanofluidic FET is comprehensively investiGated using a continuum model, composed of Nernst–Planck equations for the ionic concentrations, Poisson equation for the electric Potential, and Navier–Stokes equations for the flow field. Under the conditions of a low ionic concentration, a low surface charge density of the nanopore, and a high permittivity of the dielectric nanopore, regulation of ICR by FET is significant. The field effect on the ICR with the Gate electrode located in the middle region is opposite to that with the Gate electrode located near the tip of the nanopore.
Andrea Cavalleri - One of the best experts on this subject based on the ideXlab platform.
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Light-induced anomalous Hall effect in graphene
Nature Physics, 2019Co-Authors: J W Mciver, F.-u. Stein, G. Jotzu, G Meier, B. Schulte, T. Matsuyama, Andrea CavalleriAbstract:A transient topological response in graphene is driven by a short pulse of light. When the Fermi energy is in the predicted band gap the Hall conductance is around two conductance quanta. An ultrafast detection technique enables the measurement.AbstractMany non-equilibrium phenomena have been discovered or predicted in optically driven quantum solids^ 1 . Examples include light-induced superconductivity^ 2 , 3 and Floquet-engineered topological phases^ 4 – 8 . These are short-lived effects that should lead to measurable changes in electrical transport, which can be characterized using an ultrafast device architecture based on photoconductive switches^ 9 . Here, we report the observation of a light-induced anomalous Hall effect in monolayer graphene driven by a femtosecond pulse of circularly polarized light. The dependence of the effect on a Gate Potential used to tune the Fermi level reveals multiple features that reflect a Floquet-engineered topological band structure^ 4 , 5 , similar to the band structure originally proposed by Haldane^ 10 . This includes an approximately 60 meV wide conductance plateau centred at the Dirac point, where a gap of equal magnitude is predicted to open. We find that when the Fermi level lies within this plateau the estimated anomalous Hall conductance saturates around 1.8 ± 0.4 e ^2/ h .
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light induced anomalous hall effect in graphene
arXiv: Mesoscale and Nanoscale Physics, 2018Co-Authors: James Mciver, G. Jotzu, Andrea Cavalleri, G Meier, B. Schulte, T. Matsuyama, Falkulrich SteinAbstract:Many striking non-equilibrium phenomena have been discovered or predicted in optically-driven quantum solids, ranging from light-induced superconductivity to Floquet-engineered topological phases. These effects are expected to lead to dramatic changes in electrical transport, but can only be comprehensively characterized or functionalized with a direct interface to electrical devices that operate at ultrafast speeds. Here, we make use of laser-triggered photoconductive switches to measure the ultrafast transport properties of monolayer graphene, driven by a mid-infrared femtosecond pulse of circularly polarized light. The goal of this experiment is to probe the transport signatures of a predicted light-induced topological band structure in graphene, similar to the one originally proposed by Haldane. We report the observation of an anomalous Hall effect in the absence of an applied magnetic field. We also extract quantitative properties of the non-equilibrium state. The dependence of the effect on a Gate Potential used to tune the Fermi level reveals multiple features that reflect the effective band structure expected from Floquet theory. This includes a ~60 meV wide conductance plateau centered at the Dirac point, where a gap of approximately equal magnitude is expected to open. We also find that when the Fermi level lies within this plateau, the estimated anomalous Hall conductance saturates around ~1.8$\pm$0.4 e$^2$/h.
Pyung Choi - One of the best experts on this subject based on the ideXlab platform.
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an fet type charge sensor for highly sensitive detection of dna sequence
Biosensors and Bioelectronics, 2004Co-Authors: Yongtaek Jeong, Jangkyoo Shin, Heyjung Park, Pyung ChoiAbstract:Abstract We have fabricated an field effect transistor (FET)-type DNA charge sensor based on 0.5 μm standard complementary metal oxide semiconductor (CMOS) technology which can detect the deoxyribonucleic acid (DNA) probe’s immobilization and information on hybridization by sensing the variation of drain current due to DNA charge and investiGated its electrical characteristics. FET-type charge sensor for detecting DNA sequence is a semiconductor sensor measuring the change of electric charge caused by DNA probe’s immobilization on the Gate metal, based on the field effect mechanism of MOSFET. It was fabricated in p-channel (P) MOSFET-type because the phosphate groups present in DNA have a negative charge and this charge determines the effective Gate Potential of PMOSFET. Gold (Au) which has a chemical affinity with thiol was used as the Gate metal in order to immobilize DNA. The Gate Potential is determined by the electric charge which DNA possesses. Variation of the drain current versus time was measured. The drain current increased when thiol DNA and target DNA were injected into the solution, because of the field effect due to the electrical charge of DNA molecules. The experimental validity was verified by the results of mass changes detected using quartz crystal microbalance (QCM) under the same measurement condition. Therefore it is confirmed that DNA sequence can be detected by measuring the variation of the drain current due to the variation of DNA charge and the proposed FET-type DNA charge sensor might be useful in the development for DNA chips.
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field effect transistor based bimolecular sensor employing a pt reference electrode for the detection of deoxyribonucleic acid sequence
Japanese Journal of Applied Physics, 2004Co-Authors: Heyjung Park, Jangkyoo Shin, Hwanmok Jung, Pyung ChoiAbstract:We have fabricated field effect transistor (FET)-type biomolecular sensor for the detection of the deoxyribonucleic acid (DNA) sequence based on 0.5 µm standard complementary metal oxide semiconductor (CMOS) technology and investiGated its electrical characteristics. A Pt reference electrode with improved performance was employed for the detection of the DNA sequence and Au, which has a chemical affinity with thiol by forming a self-assembled monolayer (SAM), was used as the Gate metal in order to immobilize the DNA. It was fabricated as a p-channel metal oxide semiconductor (PMOS) FET-type because PMOSFET with positive surface Potential could be very attractive for detecting negatively charged DNA from the view point of high sensitivity and fast response time. The FET-based biomolecular sensor can detect the DNA sequence by measuring the variation of drain current due to a biomolecular charge after DNA probe immobilization and variation of capacitance after DNA hybridization. The Gate Potential of the sensor was applied by the Pt reference electrode and DNA was detected by both in situ and ex situ measurements. The drain current increased when a single-stranded DNA (ss-DNA) with thiol was immobilized because the effect of DNA charge with thiol is dominant. The drain current decreased when the DNA was hybridized into a double-stranded DNA (ds-DNA) because of the decrease in capacitance due to DNA hybridization. In situ measurement showed good agreement with ex situ measurement.
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field effect transistor based bimolecular sensor employing a pt reference electrode for the detection of deoxyribonucleic acid sequence
Japanese Journal of Applied Physics, 2004Co-Authors: Heyjung Park, Jangkyoo Shin, Hwanmok Jung, Pyung ChoiAbstract:We have fabricated field effect transistor (FET)-type biomolecular sensor for the detection of the deoxyribonucleic acid (DNA) sequence based on 0.5 µm standard complementary metal oxide semiconductor (CMOS) technology and investiGated its electrical characteristics. A Pt reference electrode with improved performance was employed for the detection of the DNA sequence and Au, which has a chemical affinity with thiol by forming a self-assembled monolayer (SAM), was used as the Gate metal in order to immobilize the DNA. It was fabricated as a p-channel metal oxide semiconductor (PMOS) FET-type because PMOSFET with positive surface Potential could be very attractive for detecting negatively charged DNA from the view point of high sensitivity and fast response time. The FET-based biomolecular sensor can detect the DNA sequence by measuring the variation of drain current due to a biomolecular charge after DNA probe immobilization and variation of capacitance after DNA hybridization. The Gate Potential of the sensor was applied by the Pt reference electrode and DNA was detected by both in situ and ex situ measurements. The drain current increased when a single-stranded DNA (ss-DNA) with thiol was immobilized because the effect of DNA charge with thiol is dominant. The drain current decreased when the DNA was hybridized into a double-stranded DNA (ds-DNA) because of the decrease in capacitance due to DNA hybridization. In situ measurement showed good agreement with ex situ measurement.
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fabrication and characteristics of a field effect transistor type charge sensor for detecting deoxyribonucleic acid sequence
Japanese Journal of Applied Physics, 2003Co-Authors: Dongsun Kim, Jangkyoo Shin, Heyjung Park, Pyung Choi, Yongtaek Jeong, Hongkun Lyu, Hyoung Sik Kim, Jonghyun Lee, Geunbae Lim, Makoto IshidaAbstract:We have fabricated an field effect transistor (FET)-type deoxyribonucleic acid (DNA) charge sensor which can detect the DNA sequence by sensing the variation of drain current due to DNA hybridization and investiGated its electrical characteristics. It is fabricated as a PMOSFET-type because the DNA probe has a negative charge. Au which has a chemical affinity with thiol was used as the Gate metal in order to immobilize DNA. The operating principle is very similar to that of MOSFET. The Gate Potential is determined by the electric charge possessed by the DNA. The variation of the drain current with time was measured. The drain current increased when thiol DNA and target DNA were injected into the solution, because of the field effect due to the electrical charge of DNA molecules. Therefore it is confirmed that the DNA sequence can be detected by measuring the variation of the drain current due to the variation of DNA charge and it is concluded that the proposed FET-type DNA charge sensor might be useful for the implementation of the DNA chip.
Phaedon Avouris - One of the best experts on this subject based on the ideXlab platform.
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band to band tunneling in carbon nanotube field effect transistors
Physical Review Letters, 2004Co-Authors: Joerg Appenzeller, J Knoch, Phaedon AvourisAbstract:: A detailed study on the mechanism of band-to-band tunneling in carbon nanotube field-effect transistors (CNFETs) is presented. Through a dual-Gated CNFET structure tunneling currents from the valence into the conduction band and vice versa can be enabled or disabled by changing the Gate Potential. Different from a conventional device where the Fermi distribution ultimately limits the Gate voltage range for switching the device on or off, current flow is controlled here by the valence and conduction band edges in a bandpass-filter-like arrangement. We discuss how the structure of the nanotube is the key enabler of this particular one-dimensional tunneling effect.
Heyjung Park - One of the best experts on this subject based on the ideXlab platform.
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an fet type charge sensor for highly sensitive detection of dna sequence
Biosensors and Bioelectronics, 2004Co-Authors: Yongtaek Jeong, Jangkyoo Shin, Heyjung Park, Pyung ChoiAbstract:Abstract We have fabricated an field effect transistor (FET)-type DNA charge sensor based on 0.5 μm standard complementary metal oxide semiconductor (CMOS) technology which can detect the deoxyribonucleic acid (DNA) probe’s immobilization and information on hybridization by sensing the variation of drain current due to DNA charge and investiGated its electrical characteristics. FET-type charge sensor for detecting DNA sequence is a semiconductor sensor measuring the change of electric charge caused by DNA probe’s immobilization on the Gate metal, based on the field effect mechanism of MOSFET. It was fabricated in p-channel (P) MOSFET-type because the phosphate groups present in DNA have a negative charge and this charge determines the effective Gate Potential of PMOSFET. Gold (Au) which has a chemical affinity with thiol was used as the Gate metal in order to immobilize DNA. The Gate Potential is determined by the electric charge which DNA possesses. Variation of the drain current versus time was measured. The drain current increased when thiol DNA and target DNA were injected into the solution, because of the field effect due to the electrical charge of DNA molecules. The experimental validity was verified by the results of mass changes detected using quartz crystal microbalance (QCM) under the same measurement condition. Therefore it is confirmed that DNA sequence can be detected by measuring the variation of the drain current due to the variation of DNA charge and the proposed FET-type DNA charge sensor might be useful in the development for DNA chips.
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field effect transistor based bimolecular sensor employing a pt reference electrode for the detection of deoxyribonucleic acid sequence
Japanese Journal of Applied Physics, 2004Co-Authors: Heyjung Park, Jangkyoo Shin, Hwanmok Jung, Pyung ChoiAbstract:We have fabricated field effect transistor (FET)-type biomolecular sensor for the detection of the deoxyribonucleic acid (DNA) sequence based on 0.5 µm standard complementary metal oxide semiconductor (CMOS) technology and investiGated its electrical characteristics. A Pt reference electrode with improved performance was employed for the detection of the DNA sequence and Au, which has a chemical affinity with thiol by forming a self-assembled monolayer (SAM), was used as the Gate metal in order to immobilize the DNA. It was fabricated as a p-channel metal oxide semiconductor (PMOS) FET-type because PMOSFET with positive surface Potential could be very attractive for detecting negatively charged DNA from the view point of high sensitivity and fast response time. The FET-based biomolecular sensor can detect the DNA sequence by measuring the variation of drain current due to a biomolecular charge after DNA probe immobilization and variation of capacitance after DNA hybridization. The Gate Potential of the sensor was applied by the Pt reference electrode and DNA was detected by both in situ and ex situ measurements. The drain current increased when a single-stranded DNA (ss-DNA) with thiol was immobilized because the effect of DNA charge with thiol is dominant. The drain current decreased when the DNA was hybridized into a double-stranded DNA (ds-DNA) because of the decrease in capacitance due to DNA hybridization. In situ measurement showed good agreement with ex situ measurement.
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field effect transistor based bimolecular sensor employing a pt reference electrode for the detection of deoxyribonucleic acid sequence
Japanese Journal of Applied Physics, 2004Co-Authors: Heyjung Park, Jangkyoo Shin, Hwanmok Jung, Pyung ChoiAbstract:We have fabricated field effect transistor (FET)-type biomolecular sensor for the detection of the deoxyribonucleic acid (DNA) sequence based on 0.5 µm standard complementary metal oxide semiconductor (CMOS) technology and investiGated its electrical characteristics. A Pt reference electrode with improved performance was employed for the detection of the DNA sequence and Au, which has a chemical affinity with thiol by forming a self-assembled monolayer (SAM), was used as the Gate metal in order to immobilize the DNA. It was fabricated as a p-channel metal oxide semiconductor (PMOS) FET-type because PMOSFET with positive surface Potential could be very attractive for detecting negatively charged DNA from the view point of high sensitivity and fast response time. The FET-based biomolecular sensor can detect the DNA sequence by measuring the variation of drain current due to a biomolecular charge after DNA probe immobilization and variation of capacitance after DNA hybridization. The Gate Potential of the sensor was applied by the Pt reference electrode and DNA was detected by both in situ and ex situ measurements. The drain current increased when a single-stranded DNA (ss-DNA) with thiol was immobilized because the effect of DNA charge with thiol is dominant. The drain current decreased when the DNA was hybridized into a double-stranded DNA (ds-DNA) because of the decrease in capacitance due to DNA hybridization. In situ measurement showed good agreement with ex situ measurement.
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fabrication and characteristics of a field effect transistor type charge sensor for detecting deoxyribonucleic acid sequence
Japanese Journal of Applied Physics, 2003Co-Authors: Dongsun Kim, Jangkyoo Shin, Heyjung Park, Pyung Choi, Yongtaek Jeong, Hongkun Lyu, Hyoung Sik Kim, Jonghyun Lee, Geunbae Lim, Makoto IshidaAbstract:We have fabricated an field effect transistor (FET)-type deoxyribonucleic acid (DNA) charge sensor which can detect the DNA sequence by sensing the variation of drain current due to DNA hybridization and investiGated its electrical characteristics. It is fabricated as a PMOSFET-type because the DNA probe has a negative charge. Au which has a chemical affinity with thiol was used as the Gate metal in order to immobilize DNA. The operating principle is very similar to that of MOSFET. The Gate Potential is determined by the electric charge possessed by the DNA. The variation of the drain current with time was measured. The drain current increased when thiol DNA and target DNA were injected into the solution, because of the field effect due to the electrical charge of DNA molecules. Therefore it is confirmed that the DNA sequence can be detected by measuring the variation of the drain current due to the variation of DNA charge and it is concluded that the proposed FET-type DNA charge sensor might be useful for the implementation of the DNA chip.