In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate and analyze the characteristics of single bio-molecules. To accurately and flexibly control the move...In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate and analyze the characteristics of single bio-molecules. To accurately and flexibly control the movement of single molecule within micro-/submicro-fluidic channels, the characteristics of current signals at the initial stage of the flow are systematically studied based on a three-electrode system. The current response of micro-/submicro-fluidic channels filled with different electrolyte solutions in non-continuous external electric field are investigated. It is found, there always exists a current reversal phenomenon, which is an inherent property of the current signals in micro/submicro-fluidics Each solution has an individual critical voltage under which the steady current value is equal to zero The interaction between the steady current and external applied voltage follows an exponential function. All these results can be attributed to the overpotentials of the electric double layer on the electrodes. These results are helpful for the design and fabrication of functional micro/nano-scale fluidic sensors and biochips.展开更多
As one of the most important realizations of stimulated emission depletion (STED) microscopy, the continuous- wave (CW) STED system, constructed by using CW lasers as the excitation and STED beams, has been invest...As one of the most important realizations of stimulated emission depletion (STED) microscopy, the continuous- wave (CW) STED system, constructed by using CW lasers as the excitation and STED beams, has been investigated and developed for nearly a decade. However, a theoretical model of the suppression factors in CW STED has not been well established. In this investigation, the factors that affect the spatial resolution of a CW STED system are theoretically and numerically studied. The full-width-at-half-maximum (FWHM) of a CW STED with a doughnut-shaped STED beam is also reanalyzed. It is found that the suppression function is dominated by the ratio of the local STED and excitation beam intensities. In addition, the FWHM is highly sensitive to both the fluorescence rate (inverse of fluoresce lifetime) and the quenching rate, but insensitive to the rate of vibrational relaxation. For comparison, the suppression function in picosecond STED is only determined by the distribution of the STED beam intensity scaled with the saturation intensity. Our model is highly consistent with published experimental data for evaluating the spatial resolution. This investigation is important in guiding the development of new CW STED systems.展开更多
The electrodynamic characteristics of single DNA molecules moving within micro-/nano-fluidic channels are important in the design of biomedical chips and bimolecular sensors. In this study, the dynamic properties of ...The electrodynamic characteristics of single DNA molecules moving within micro-/nano-fluidic channels are important in the design of biomedical chips and bimolecular sensors. In this study, the dynamic properties of λ-DNA molecules transferring along the microchannels driven by the external electrickinetic force were systemically investigated with the single molecule fluorescence imaging technique. The experimental results indicated that the velocity of DNA molecules was strictly dependent on the value of the applied electric field and the diameter of the channel. The larger the external electric field, the larger the velocity, and the more significant deformation of DNA molecules. More meaningfully, it was found that the moving directions of DNA molecules had two completely different directions:(i) along the direction of the external electric field, when the electric field intensity was smaller than a certain threshold value;(ii) opposite to the direction of the external electric field, when the electric field intensity was greater than the threshold electric field intensity.The reversal movement of DNA molecules was mainly determined by the competition between the electrophoresis force and the influence of electro-osmosis flow. These new findings will theoretically guide the practical application of fluidic channel sensors and lab-on-chips for precisely manipulating single DNA molecules.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61378083 and 11672229)the International Cooperation Foundation of the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011DFA12220)+2 种基金the Major Research Plan of the National Natural Science Foundation of China(Grant No.91123030)the Natural Science Foundation of Shaanxi Province of China(Grant Nos.2010JS110,14JS106,14JS107,and 2013SZS03-Z01)the Natural Science Basic Research Program of Shaanxi Province-Major Basic Research Project(Grant No.2016ZDJC-15)
文摘In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate and analyze the characteristics of single bio-molecules. To accurately and flexibly control the movement of single molecule within micro-/submicro-fluidic channels, the characteristics of current signals at the initial stage of the flow are systematically studied based on a three-electrode system. The current response of micro-/submicro-fluidic channels filled with different electrolyte solutions in non-continuous external electric field are investigated. It is found, there always exists a current reversal phenomenon, which is an inherent property of the current signals in micro/submicro-fluidics Each solution has an individual critical voltage under which the steady current value is equal to zero The interaction between the steady current and external applied voltage follows an exponential function. All these results can be attributed to the overpotentials of the electric double layer on the electrodes. These results are helpful for the design and fabrication of functional micro/nano-scale fluidic sensors and biochips.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11672229 and 61378083)International Cooperation Foundation of the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011DFA12220)+4 种基金Major Research Plan of the National Natural Science Foundation of China(Grant No.91123030)Natural Science Foundation of Shaanxi Province of China(Grant Nos.2010JS110and 2013SZS03-Z01)Natural Science Basic Research Program of Shaanxi Province-Major Basic Research Project,China(Grant No.2016ZDJC-15)Young Scientist Fund of the National Natural Science Foundation of China(Grant No.11504294)the Youth Talent Plan of the Natural Science Foundation of Shaanxi Province of China(Grant No.2016JQ103)
文摘As one of the most important realizations of stimulated emission depletion (STED) microscopy, the continuous- wave (CW) STED system, constructed by using CW lasers as the excitation and STED beams, has been investigated and developed for nearly a decade. However, a theoretical model of the suppression factors in CW STED has not been well established. In this investigation, the factors that affect the spatial resolution of a CW STED system are theoretically and numerically studied. The full-width-at-half-maximum (FWHM) of a CW STED with a doughnut-shaped STED beam is also reanalyzed. It is found that the suppression function is dominated by the ratio of the local STED and excitation beam intensities. In addition, the FWHM is highly sensitive to both the fluorescence rate (inverse of fluoresce lifetime) and the quenching rate, but insensitive to the rate of vibrational relaxation. For comparison, the suppression function in picosecond STED is only determined by the distribution of the STED beam intensity scaled with the saturation intensity. Our model is highly consistent with published experimental data for evaluating the spatial resolution. This investigation is important in guiding the development of new CW STED systems.
基金Project supported by the National Natural Science Foundation of China(Grant No.61378083)the International Cooperation Foundation of the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011DFA12220)+1 种基金the Major Research Plan of National Natural Science Foundation of China(Grant No.91123030)the Natural Science Foundation of Shaanxi Province of China(Grant Nos.2010JS110 and2013SZS03-Z01)
文摘The electrodynamic characteristics of single DNA molecules moving within micro-/nano-fluidic channels are important in the design of biomedical chips and bimolecular sensors. In this study, the dynamic properties of λ-DNA molecules transferring along the microchannels driven by the external electrickinetic force were systemically investigated with the single molecule fluorescence imaging technique. The experimental results indicated that the velocity of DNA molecules was strictly dependent on the value of the applied electric field and the diameter of the channel. The larger the external electric field, the larger the velocity, and the more significant deformation of DNA molecules. More meaningfully, it was found that the moving directions of DNA molecules had two completely different directions:(i) along the direction of the external electric field, when the electric field intensity was smaller than a certain threshold value;(ii) opposite to the direction of the external electric field, when the electric field intensity was greater than the threshold electric field intensity.The reversal movement of DNA molecules was mainly determined by the competition between the electrophoresis force and the influence of electro-osmosis flow. These new findings will theoretically guide the practical application of fluidic channel sensors and lab-on-chips for precisely manipulating single DNA molecules.