Electronic interactions of the Group 2A elements with magnesium have been studied through the dilute solid solutions in binary Mg-Ca,Mg-Sr and Mg-Ba systems.This investigation incorporated the difference in the‘Work ...Electronic interactions of the Group 2A elements with magnesium have been studied through the dilute solid solutions in binary Mg-Ca,Mg-Sr and Mg-Ba systems.This investigation incorporated the difference in the‘Work Function'(ΔWF)measured via Kelvin Probe Force Microscopy(KPFM),as a property directly affected by interatomic bond types,i.e.the electronic structure,nanoindentation measurements,and Stacking Fault Energy values reported in the literature.It was shown that the nano-hardness of the solid-solutionα-Mg phase changed in the order of Mg-Ca>Mg-Sr>Mg-Ba.Thus,it was shown,by also considering the nano-hardness levels,that SFE of a solid-solution is closely correlated with its‘Work Function'level.Nano-hardness measurements on the eutectics andΔWF difference between eutectic phases enabled an assessment of the relative bond strength and the pertinent electronic structures of the eutectics in the three alloys.Correlation withΔWF and at least qualitative verification of those computed SFE values with some experimental measurement techniques were considered important as those computational methods are based on zero Kelvin degree,relatively simple atomic models and a number of assumptions.As asserted by this investigation,if the results of measurement techniques can be qualitatively correlated with those of the computational methods,it can be possible to evaluate the electronic structures in alloys,starting from binary systems,going to ternary and then multi-elemental systems.Our investigation has shown that such a qualitative correlation is possible.After all,the SFE values are not treated as absolute values but rather become essential in comparative investigations when assessing the influences of alloying elements at a fundamental level,that is,free electron density distributions.Our study indicated that the principles of‘electronic metallurgy'in developing multi-elemental alloy systems can be followed via practical experimental methods,i.e.ΔWF measurements using KPFM and nanoindentation.展开更多
Ferroelectric polymer nanocomposites possess exceptional electric properties with respect to the two otherwise uniform phases,which is commonly attributed to the critical role of the matrix-particle interfacial region...Ferroelectric polymer nanocomposites possess exceptional electric properties with respect to the two otherwise uniform phases,which is commonly attributed to the critical role of the matrix-particle interfacial region.However,the structure-property correlation of the interface remains unestablished,and thus,the design of ferroelectric polymer nanocompos-ite has largely relied on the trial-and-error method.Here,a strategy that combines multi-mode scanning probe microscopy-based electrical charac-terization and nano-infrared spectroscopy is developed to unveil the local structure-property correlation of the interface in ferroelectric polymer nano-composites.The results show that the type of surface modifiers decorated on the nanoparticles can significantly influence the local polar-phase content and the piezoelectric effect of the polymer matrix surrounding the nano-particles.The strongly coupled polar-phase content and piezoelectric effect measured directly in the interfacial region as well as the computed bonding energy suggest that the property enhancement originates from the formation of hydrogen bond between the surface modifiers and the ferroelectric polymer.It is also directly detected that the local domain size of the ferroelectric polymer can impact the energy level and distribution of charge traps in the interfacial region and eventually influence the local dielectric strength.展开更多
Electronic properties of two-dimensional(2D) materials can be strongly modulated by localized strain. The typical spatial resolution of conventional Kelvin probe force microscopy(KPFM) is usually limited in a few hund...Electronic properties of two-dimensional(2D) materials can be strongly modulated by localized strain. The typical spatial resolution of conventional Kelvin probe force microscopy(KPFM) is usually limited in a few hundreds of nanometers, and it is difficult to characterize localized electronic properties of 2D materials at nanoscales. Herein, tip-enhanced Raman spectroscopy(TERS) is proposed to combine with KPFM to break this restriction. TERS scan is conducted on ReS2bubbles deposited on a rough Au thin film to obtain strain distribution by using the Raman peak shift. The localized contact potential difference(CPD) is inversely calculated with a higher spatial resolution by using strain measured by TERS and CPD-strain working curve obtained using conventional KPFM and atomic force microscopy. This method enhances the spatial resolution of CPD measurements and can be potentially used to characterize localized electronic properties of 2D materials.展开更多
The probe effect on the apparent image of biological atomic force microscopy was explored in this study, and the potential of AFM in conformational study of gene related biological processes was illustrated by the spe...The probe effect on the apparent image of biological atomic force microscopy was explored in this study, and the potential of AFM in conformational study of gene related biological processes was illustrated by the specific nanostructural information of a new antitumor drug binding to DNA.展开更多
Blind tip reconstruction(BTR) method is one of the favorable methods to estimate the atomic force microscopy(AFM) probe shape. The exact shape of the characterizer is not required for BTR, while the geometry of the sa...Blind tip reconstruction(BTR) method is one of the favorable methods to estimate the atomic force microscopy(AFM) probe shape. The exact shape of the characterizer is not required for BTR, while the geometry of the sample may affect the reconstruction significantly. A cone-shaped array sample was chosen as a characterizer to be evaluated. The target AFM probe to be reconstructed was a diamond triangular pyramid probe with two feature angles, namely front angle(FA) and back angle(BA). Four conical structures with different semi-angles were dilated by the pyramid probe. Simulation of scanning process demonstrates that it is easy to judge from the images of the isolated rotary structure, cone-shaped, the suitability of the sample to be a tip characterizer for a pyramid probe. The cone-shaped array sample was repeatedly scanned 50 times by the diamond probe using an AFM. The series of scanning images shrank gradually and more information of the probe was exhibited in the images, indicating that the characterizer has been more suitable for BTR. The feature angle FA of the characterizer increasingly reduces during the scanning process. A self-adaptive grinding between the probe and the characterizer contributes to BTR of the diamond pyramid probe.展开更多
Scanning ion conductance microscopy(SICM) is an emerging non-destructive surface topography characterization apparatus with nanoscale resolution. However, the low regulating frequency of probe in most existing modulat...Scanning ion conductance microscopy(SICM) is an emerging non-destructive surface topography characterization apparatus with nanoscale resolution. However, the low regulating frequency of probe in most existing modulated current based SICM systems increases the system noise, and has difficulty in imaging sample surface with steep height changes. In order to enable SICM to have the capability of imaging surfaces with steep height changes, a novel probe that can be used in the modulated current based hopping mode is designed. The design relies on two piezoelectric ceramics with different travels to separate position adjustment and probe frequency regulation in the Z direction. To further improve the resonant frequency of the probe, the material and the key dimensions for each component of the probe are optimized based on the multi-objective optimization method and the finite element analysis. The optimal design has a resonant frequency of above 10 kHz. To validate the rationality of the designed probe, microstructured grating samples are imaged using the homebuilt modulated current based SICM system. The experimental results indicate that the designed high frequency probe can effectively reduce the spike noise by 26% in the average number of spike noise. The proposed design provides a feasible solution for improving the imaging quality of the existing SICM systems which normally use ordinary probes with relatively low regulating frequency.展开更多
The adsorption configurations of molecules adsorbed on substrates can significantly affect their physical and chemical properties. A standing configuration can be difficult to determine by traditional techniques, such...The adsorption configurations of molecules adsorbed on substrates can significantly affect their physical and chemical properties. A standing configuration can be difficult to determine by traditional techniques, such as scanning tunneling microscopy(STM) due to the superposition of electronic states. In this paper, we report the real-space observation of the standing adsorption configuration of phenylacetylene on Cu(111) by non-contact atomic force microscopy(nc-AFM).Deposition of phenylacetylene at 25 K shows featureless bright spots in STM images. Using nc-AFM, the line features representing the C–H and C–C bonds in benzene rings are evident, which implies a standing adsorption configuration. Further density functional theory(DFT) calculations reveal multiple optimized adsorption configurations with phenylacetylene breaking its acetylenic bond and forming C–Cu bond(s) with the underlying copper atoms, and hence stand on the substrate.By comparing the nc-AFM simulations with the experimental observation, we identify the standing adsorption configuration of phenylacetylene on Cu(111). Our work demonstrates an application of combining nc-AFM measurements and DFT calculations to the study of standing molecules on substrates, which enriches our knowledge of the adsorption behaviors of small molecules on solid surfaces at low temperatures.展开更多
The elastic indentation modulus and hardness of standard bulk materials and advanced thin films were deter-mined by using the nanoindentation technique followed by the Oliver-Pharr post-treatment. After measure-ments ...The elastic indentation modulus and hardness of standard bulk materials and advanced thin films were deter-mined by using the nanoindentation technique followed by the Oliver-Pharr post-treatment. After measure-ments with different loading/unloading schemes on chemically polished bulk titanium a substantial decrease of both modulus and hardness vs an increasing loading time was found. Then, hard nanostructured TiBN and TiCrBN thin films deposited by magnetron sputtering (using multiphase targets) on substrates of high roughness (sintered hard metal) and low roughness (silicon) were studied. Experimental modulus and hardness characterized by using two different nanoindenter tools were within the limits of standard deviation. However, a strong effect of roughness on the spread of the experimental values was observed and it was found that hard-ness and elastic indentation modulus obeyed a Gaussian distribution. The experimental data were discussed together with scanning probe microscopy (SPM) images of typical imprints taken after the nanoindentation tests and the local topography s strong correlation with the results of nanoindentation was described.展开更多
Electron trapping properties at the HfO_2/SiO_2 interface have been measured through Kelvin Probe force microscopy,between room temperature and 90 ℃.The electron diffusion in HfO_2 shows a multiple-step process.After...Electron trapping properties at the HfO_2/SiO_2 interface have been measured through Kelvin Probe force microscopy,between room temperature and 90 ℃.The electron diffusion in HfO_2 shows a multiple-step process.After injection,electrons diffuse quickly toward the HfO_2/SiO_2 interface and then diffuse laterally near the interface in two sub-steps:The first is a fast diffusion through shallow trap centers and the second is a slow diffusion through deep trap centers.Evolution of contact potential difference profile in the fast lateral diffusion sub-step was simulated by solving a diffusion equation with a term describing the charge loss.In this way,the diffusion coefficient and the average life time at different temperatures were extracted.A value of 0.57 eV was calculated for the activation energy of the shallow trap centers in HfO_2.展开更多
We demonstrate the feasibility of simultancous multi-probe detection for an optcal-resolution photoacoustic microscopy(OR-PAM)system.OR-P AM has elicited the attention of biomedical imaging researchers because of its ...We demonstrate the feasibility of simultancous multi-probe detection for an optcal-resolution photoacoustic microscopy(OR-PAM)system.OR-P AM has elicited the attention of biomedical imaging researchers because of its optical absorption contrast and high spatial resolution with great imaging depth.OR-PAM allows label-free and noninvasive imaging by maximizing the optical absorption of endogenous biomolecules.However,given the inadequate absoption of some biomolcules,detection sensitivity at the same incident intensity requires improvement.In this study,a modulated continuous wave with power density less than 3mW/cm^(2)(1/4 of the ANSI safety limit)excited the weak photoacoustic(PA)signals of biological cells.A microcavity traneducer is developed based on the bulk modulus of gas five orders of magnitude lower than that of solid;air pressure variation is inversely proportional to cavity volume at the same temperature increase.Considering that a PA wave expands in various directions,detecting PA signals from different positions and adding them together can increase detection sensitivity and signal-to-noise ratio.Therefore,we employ four detectors to acquire tiny PA signals simul-taneously.Experimental results show that the developed OR-PAM system allows the label-free imaging of cells with weak optical absorption.展开更多
The microscopic physical properties of Hardened Cement Paste (HCP) surfaces were evaluated by using Scanning Probe Microscopy (SPM). The cement pastes were cured under a hydrostatic pressure of 400 MPa and the contact...The microscopic physical properties of Hardened Cement Paste (HCP) surfaces were evaluated by using Scanning Probe Microscopy (SPM). The cement pastes were cured under a hydrostatic pressure of 400 MPa and the contacting surfaces with a slide glass during the curing were studied. Scanning Electron Microscope (SEM) observation at a magnification of 7000 revealed smooth surfaces with no holes. The surface roughness calculated from the SPM measurement was 4 nm. The surface potential and the frictional force measured by SPM were uniform throughout the measured area 24 h after the curing. However, spots of low surface potential and stains of low frictional force and low viscoelasticity were observed one month after curing. This change was attributed to the carbonation of hydrates.展开更多
为解决原子力显微镜(Atomic Force Microscope,AFM)系统更换探针后光路调整复杂耗时、精度不足的问题,本文首次提出通过精密控制探针与探针夹装配位置来实现更换的探针相对AFM系统原光路位置的一致,进而实现免去AFM系统换针后调整光路...为解决原子力显微镜(Atomic Force Microscope,AFM)系统更换探针后光路调整复杂耗时、精度不足的问题,本文首次提出通过精密控制探针与探针夹装配位置来实现更换的探针相对AFM系统原光路位置的一致,进而实现免去AFM系统换针后调整光路步骤。该系统的光路一致性组件采用光束偏转法对探针位置与偏转进行放大与监测,并使用高精度位移与角度调节平台进行探针相对于探针夹的方位调整。通过实物搭建对探针一致性效果进行了验证,并对紫外光(Ultraviolet,UV)胶水固化过程导致探针位置偏移影响;探针不同偏移量时产生的探测器噪音对AFM系统成像质量影响进行了系统分析。实验结果表明:经由该系统装配的探针平均位置精度接近1.1μm;并且在AFM系统中更换一致性探针仅需8 s。该系统实现了高精度且质量稳定的探针一致性装配,极大地简化了AFM系统重新校准光路的操作步骤,其与自动换针装置配合可有效提升工业计量型AFM的操作与测量性能。展开更多
原子力显微镜(atomic force microscopy,AFM)在微纳米尺度力学测量领域有着广泛应用,其微悬臂梁探针的弹性常数是直接影响测量结果准确性的关键因素之一。弯曲法是标定微悬臂梁弹性常数的一类重要方法,基于弯曲标定原理提出了一种新的...原子力显微镜(atomic force microscopy,AFM)在微纳米尺度力学测量领域有着广泛应用,其微悬臂梁探针的弹性常数是直接影响测量结果准确性的关键因素之一。弯曲法是标定微悬臂梁弹性常数的一类重要方法,基于弯曲标定原理提出了一种新的技术实现方案,并研制了相应的标定系统。借助精密运动定位台使微悬臂梁接触超精密天平并产生弯曲,分别以天平和光杠杆机构同步测得接触力和梁的弯曲量,再根据胡克定律直接算得弹性常数。利用所研制的系统对多种型号的微悬臂梁进行了标定,实验结果表明该系统具有良好的准确性和重复性,测量相对标准差小于5%。展开更多
基金financial support for this work provided by Eski sehir Technical University Scientific Research Projects Unit with Grant Number 20DRP059support provided by the Turkish Ministry of Science,Industry and Technology under the SANTEZ Project 0286.STZ.2013±2。
文摘Electronic interactions of the Group 2A elements with magnesium have been studied through the dilute solid solutions in binary Mg-Ca,Mg-Sr and Mg-Ba systems.This investigation incorporated the difference in the‘Work Function'(ΔWF)measured via Kelvin Probe Force Microscopy(KPFM),as a property directly affected by interatomic bond types,i.e.the electronic structure,nanoindentation measurements,and Stacking Fault Energy values reported in the literature.It was shown that the nano-hardness of the solid-solutionα-Mg phase changed in the order of Mg-Ca>Mg-Sr>Mg-Ba.Thus,it was shown,by also considering the nano-hardness levels,that SFE of a solid-solution is closely correlated with its‘Work Function'level.Nano-hardness measurements on the eutectics andΔWF difference between eutectic phases enabled an assessment of the relative bond strength and the pertinent electronic structures of the eutectics in the three alloys.Correlation withΔWF and at least qualitative verification of those computed SFE values with some experimental measurement techniques were considered important as those computational methods are based on zero Kelvin degree,relatively simple atomic models and a number of assumptions.As asserted by this investigation,if the results of measurement techniques can be qualitatively correlated with those of the computational methods,it can be possible to evaluate the electronic structures in alloys,starting from binary systems,going to ternary and then multi-elemental systems.Our investigation has shown that such a qualitative correlation is possible.After all,the SFE values are not treated as absolute values but rather become essential in comparative investigations when assessing the influences of alloying elements at a fundamental level,that is,free electron density distributions.Our study indicated that the principles of‘electronic metallurgy'in developing multi-elemental alloy systems can be followed via practical experimental methods,i.e.ΔWF measurements using KPFM and nanoindentation.
基金supported by the National Natural Science Foundation of China(Nos.51922056 and 51921005).
文摘Ferroelectric polymer nanocomposites possess exceptional electric properties with respect to the two otherwise uniform phases,which is commonly attributed to the critical role of the matrix-particle interfacial region.However,the structure-property correlation of the interface remains unestablished,and thus,the design of ferroelectric polymer nanocompos-ite has largely relied on the trial-and-error method.Here,a strategy that combines multi-mode scanning probe microscopy-based electrical charac-terization and nano-infrared spectroscopy is developed to unveil the local structure-property correlation of the interface in ferroelectric polymer nano-composites.The results show that the type of surface modifiers decorated on the nanoparticles can significantly influence the local polar-phase content and the piezoelectric effect of the polymer matrix surrounding the nano-particles.The strongly coupled polar-phase content and piezoelectric effect measured directly in the interfacial region as well as the computed bonding energy suggest that the property enhancement originates from the formation of hydrogen bond between the surface modifiers and the ferroelectric polymer.It is also directly detected that the local domain size of the ferroelectric polymer can impact the energy level and distribution of charge traps in the interfacial region and eventually influence the local dielectric strength.
基金Project supported by the Zhejiang Provincial Natural Science Foundation of China (Grant No. LZ22A040003)the National Natural Science Foundation of China (Grant No. 52027809)。
文摘Electronic properties of two-dimensional(2D) materials can be strongly modulated by localized strain. The typical spatial resolution of conventional Kelvin probe force microscopy(KPFM) is usually limited in a few hundreds of nanometers, and it is difficult to characterize localized electronic properties of 2D materials at nanoscales. Herein, tip-enhanced Raman spectroscopy(TERS) is proposed to combine with KPFM to break this restriction. TERS scan is conducted on ReS2bubbles deposited on a rough Au thin film to obtain strain distribution by using the Raman peak shift. The localized contact potential difference(CPD) is inversely calculated with a higher spatial resolution by using strain measured by TERS and CPD-strain working curve obtained using conventional KPFM and atomic force microscopy. This method enhances the spatial resolution of CPD measurements and can be potentially used to characterize localized electronic properties of 2D materials.
基金The support from Visiting Scholar Foundation of Key Lab in University and Chinese Education Foundation for Excellent Young Teachers as well as the support from Jiangsu province (BJ 99011 and BK 2001401) is greatly appreciated.
文摘The probe effect on the apparent image of biological atomic force microscopy was explored in this study, and the potential of AFM in conformational study of gene related biological processes was illustrated by the specific nanostructural information of a new antitumor drug binding to DNA.
基金supported by the National Natural Science Foundation of China(Grant No.51305298,No.51675379)Tianjin Research Program of Application Foundation and Advanced Technology(Grant No.13JCQNJC04700)
文摘Blind tip reconstruction(BTR) method is one of the favorable methods to estimate the atomic force microscopy(AFM) probe shape. The exact shape of the characterizer is not required for BTR, while the geometry of the sample may affect the reconstruction significantly. A cone-shaped array sample was chosen as a characterizer to be evaluated. The target AFM probe to be reconstructed was a diamond triangular pyramid probe with two feature angles, namely front angle(FA) and back angle(BA). Four conical structures with different semi-angles were dilated by the pyramid probe. Simulation of scanning process demonstrates that it is easy to judge from the images of the isolated rotary structure, cone-shaped, the suitability of the sample to be a tip characterizer for a pyramid probe. The cone-shaped array sample was repeatedly scanned 50 times by the diamond probe using an AFM. The series of scanning images shrank gradually and more information of the probe was exhibited in the images, indicating that the characterizer has been more suitable for BTR. The feature angle FA of the characterizer increasingly reduces during the scanning process. A self-adaptive grinding between the probe and the characterizer contributes to BTR of the diamond pyramid probe.
基金Supported by National Natural Science Foundation of China(Grant No.51375363)
文摘Scanning ion conductance microscopy(SICM) is an emerging non-destructive surface topography characterization apparatus with nanoscale resolution. However, the low regulating frequency of probe in most existing modulated current based SICM systems increases the system noise, and has difficulty in imaging sample surface with steep height changes. In order to enable SICM to have the capability of imaging surfaces with steep height changes, a novel probe that can be used in the modulated current based hopping mode is designed. The design relies on two piezoelectric ceramics with different travels to separate position adjustment and probe frequency regulation in the Z direction. To further improve the resonant frequency of the probe, the material and the key dimensions for each component of the probe are optimized based on the multi-objective optimization method and the finite element analysis. The optimal design has a resonant frequency of above 10 kHz. To validate the rationality of the designed probe, microstructured grating samples are imaged using the homebuilt modulated current based SICM system. The experimental results indicate that the designed high frequency probe can effectively reduce the spike noise by 26% in the average number of spike noise. The proposed design provides a feasible solution for improving the imaging quality of the existing SICM systems which normally use ordinary probes with relatively low regulating frequency.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2016YFA0202300 and 2018YFA0305800)the National Natural Science Foundation of China(Grant Nos.61888102,61474141,and 21661132006)+2 种基金the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.11604373)the Outstanding Youth Science Foundation,China(Grant No.61622116)the Strategic Priority Research Program of Chinese Academy of Sciences(CAS)(Grant Nos.XDB28000000 and XDB30000000)
文摘The adsorption configurations of molecules adsorbed on substrates can significantly affect their physical and chemical properties. A standing configuration can be difficult to determine by traditional techniques, such as scanning tunneling microscopy(STM) due to the superposition of electronic states. In this paper, we report the real-space observation of the standing adsorption configuration of phenylacetylene on Cu(111) by non-contact atomic force microscopy(nc-AFM).Deposition of phenylacetylene at 25 K shows featureless bright spots in STM images. Using nc-AFM, the line features representing the C–H and C–C bonds in benzene rings are evident, which implies a standing adsorption configuration. Further density functional theory(DFT) calculations reveal multiple optimized adsorption configurations with phenylacetylene breaking its acetylenic bond and forming C–Cu bond(s) with the underlying copper atoms, and hence stand on the substrate.By comparing the nc-AFM simulations with the experimental observation, we identify the standing adsorption configuration of phenylacetylene on Cu(111). Our work demonstrates an application of combining nc-AFM measurements and DFT calculations to the study of standing molecules on substrates, which enriches our knowledge of the adsorption behaviors of small molecules on solid surfaces at low temperatures.
基金supported by the "Communauté Franaise de Belgique-ARC 04/09-310"was done in the context of the EC VI FW international EXCELL Project
文摘The elastic indentation modulus and hardness of standard bulk materials and advanced thin films were deter-mined by using the nanoindentation technique followed by the Oliver-Pharr post-treatment. After measure-ments with different loading/unloading schemes on chemically polished bulk titanium a substantial decrease of both modulus and hardness vs an increasing loading time was found. Then, hard nanostructured TiBN and TiCrBN thin films deposited by magnetron sputtering (using multiphase targets) on substrates of high roughness (sintered hard metal) and low roughness (silicon) were studied. Experimental modulus and hardness characterized by using two different nanoindenter tools were within the limits of standard deviation. However, a strong effect of roughness on the spread of the experimental values was observed and it was found that hard-ness and elastic indentation modulus obeyed a Gaussian distribution. The experimental data were discussed together with scanning probe microscopy (SPM) images of typical imprints taken after the nanoindentation tests and the local topography s strong correlation with the results of nanoindentation was described.
基金supported by the National Natural Science Foundation of China(Grant No.61176080)
文摘Electron trapping properties at the HfO_2/SiO_2 interface have been measured through Kelvin Probe force microscopy,between room temperature and 90 ℃.The electron diffusion in HfO_2 shows a multiple-step process.After injection,electrons diffuse quickly toward the HfO_2/SiO_2 interface and then diffuse laterally near the interface in two sub-steps:The first is a fast diffusion through shallow trap centers and the second is a slow diffusion through deep trap centers.Evolution of contact potential difference profile in the fast lateral diffusion sub-step was simulated by solving a diffusion equation with a term describing the charge loss.In this way,the diffusion coefficient and the average life time at different temperatures were extracted.A value of 0.57 eV was calculated for the activation energy of the shallow trap centers in HfO_2.
基金supported by the National Natural Science Foundation of China(Grant No.61178086)Science and Technology Program of Guangzhou,China(Grant No.2012J4300138)Foundation for Distinguished Young Talents in South China Normal University,China.(Grant No.2012KJ010).
文摘We demonstrate the feasibility of simultancous multi-probe detection for an optcal-resolution photoacoustic microscopy(OR-PAM)system.OR-P AM has elicited the attention of biomedical imaging researchers because of its optical absorption contrast and high spatial resolution with great imaging depth.OR-PAM allows label-free and noninvasive imaging by maximizing the optical absorption of endogenous biomolecules.However,given the inadequate absoption of some biomolcules,detection sensitivity at the same incident intensity requires improvement.In this study,a modulated continuous wave with power density less than 3mW/cm^(2)(1/4 of the ANSI safety limit)excited the weak photoacoustic(PA)signals of biological cells.A microcavity traneducer is developed based on the bulk modulus of gas five orders of magnitude lower than that of solid;air pressure variation is inversely proportional to cavity volume at the same temperature increase.Considering that a PA wave expands in various directions,detecting PA signals from different positions and adding them together can increase detection sensitivity and signal-to-noise ratio.Therefore,we employ four detectors to acquire tiny PA signals simul-taneously.Experimental results show that the developed OR-PAM system allows the label-free imaging of cells with weak optical absorption.
文摘The microscopic physical properties of Hardened Cement Paste (HCP) surfaces were evaluated by using Scanning Probe Microscopy (SPM). The cement pastes were cured under a hydrostatic pressure of 400 MPa and the contacting surfaces with a slide glass during the curing were studied. Scanning Electron Microscope (SEM) observation at a magnification of 7000 revealed smooth surfaces with no holes. The surface roughness calculated from the SPM measurement was 4 nm. The surface potential and the frictional force measured by SPM were uniform throughout the measured area 24 h after the curing. However, spots of low surface potential and stains of low frictional force and low viscoelasticity were observed one month after curing. This change was attributed to the carbonation of hydrates.
文摘为解决原子力显微镜(Atomic Force Microscope,AFM)系统更换探针后光路调整复杂耗时、精度不足的问题,本文首次提出通过精密控制探针与探针夹装配位置来实现更换的探针相对AFM系统原光路位置的一致,进而实现免去AFM系统换针后调整光路步骤。该系统的光路一致性组件采用光束偏转法对探针位置与偏转进行放大与监测,并使用高精度位移与角度调节平台进行探针相对于探针夹的方位调整。通过实物搭建对探针一致性效果进行了验证,并对紫外光(Ultraviolet,UV)胶水固化过程导致探针位置偏移影响;探针不同偏移量时产生的探测器噪音对AFM系统成像质量影响进行了系统分析。实验结果表明:经由该系统装配的探针平均位置精度接近1.1μm;并且在AFM系统中更换一致性探针仅需8 s。该系统实现了高精度且质量稳定的探针一致性装配,极大地简化了AFM系统重新校准光路的操作步骤,其与自动换针装置配合可有效提升工业计量型AFM的操作与测量性能。
文摘原子力显微镜(atomic force microscopy,AFM)在微纳米尺度力学测量领域有着广泛应用,其微悬臂梁探针的弹性常数是直接影响测量结果准确性的关键因素之一。弯曲法是标定微悬臂梁弹性常数的一类重要方法,基于弯曲标定原理提出了一种新的技术实现方案,并研制了相应的标定系统。借助精密运动定位台使微悬臂梁接触超精密天平并产生弯曲,分别以天平和光杠杆机构同步测得接触力和梁的弯曲量,再根据胡克定律直接算得弹性常数。利用所研制的系统对多种型号的微悬臂梁进行了标定,实验结果表明该系统具有良好的准确性和重复性,测量相对标准差小于5%。