The periodic impact force induced by tip-sample contact in a tapping mode atomic force microscope （AFM） gives rise to the non-harmonic response of a micro-cantilever. These non-harmonic signals contain the full char...The periodic impact force induced by tip-sample contact in a tapping mode atomic force microscope （AFM） gives rise to the non-harmonic response of a micro-cantilever. These non-harmonic signals contain the full characteristics of tip-sample interaction. A complete theoretical model describing the dynamical behaviour of tip-sample system was developed in this paper. An analytic formula was introduced to describe the relationship between time-varying tip-sample impact force and tip motion. The theoretical analysis and numerical results both show that the timevarying tip-sample impact force can be reconstructed by recording tip motion. This allows for the reconstruction of the characteristics of the tip-sample force, like contact time and maximum contact force. It can also explain the ability of AFM higher harmonics imaging in mapping stiffness and surface energy variations.展开更多
A standard calibration grating was used for image scanning to investigate the effect of hydration films on imaging resolution by Atomic Force Microscope （AFM）. The results showed that the hydration films greatly aff...A standard calibration grating was used for image scanning to investigate the effect of hydration films on imaging resolution by Atomic Force Microscope （AFM）. The results showed that the hydration films greatly affect the imaging resolution for the tapping mode, but no evident effect on the contact mode, The possible reasons for the effect of hydration films on scanning images of AFM are also brought forward here.展开更多
原子力显微镜(Atomic Force Microscopy,AFM)成像常用于研究多糖分子结构,然而针对阴离子多糖,现有的制样方法较难在小范围观察区获得其清晰的单分子束结构图片。因此,本文以黄原胶为阴离子多糖代表,从不改变多糖本身结构、提升成像质...原子力显微镜(Atomic Force Microscopy,AFM)成像常用于研究多糖分子结构,然而针对阴离子多糖,现有的制样方法较难在小范围观察区获得其清晰的单分子束结构图片。因此,本文以黄原胶为阴离子多糖代表,从不改变多糖本身结构、提升成像质量角度出发,对多糖样品浓度,云母片不同金属离子盐种类、浓度和处理时间等AFM制样方法进行了优化。结果表明,在空白云母片上,黄原胶浓度1~5μg/mL时可观测到多糖单分子束结构,但在15μm×15μm扫描范围内可观测的分子束较少。通过对云母片进行处理优化,最佳处理条件选定在0.5 mmol/L的CaCl_(2)溶液处理2 min或2 mmol/L CaCl_(2)溶液处理0.5 min。在此条件下,当黄原胶浓度为5μg/mL时,在3μm×3μm观测范围内,处理后云母片上的黄原胶分子束数量及成像质量相比空白云母片显著提升,且其单分子束高度与分子结构并未发生改变。此外,通过提高云母片干燥温度可以获取更均匀的黄原胶分子结构图片。本研究可为其他阴离子多糖AFM成像的样品制备提供可借鉴的方法参考。展开更多
Dynamic friction occurs not only between two contact objects sliding against each other,but also between two relative sliding surfaces several nanometres apart.Many emerging micro-and nano-mechanical systems that prom...Dynamic friction occurs not only between two contact objects sliding against each other,but also between two relative sliding surfaces several nanometres apart.Many emerging micro-and nano-mechanical systems that promise new applications in sensors or information technology may suffer or benefit from noncontact friction.Herein we demonstrate the distance-dependent friction energy dissipation between the tip and the heterogeneous polymers by the bimodal atomic force microscopy(AFM)method driving the second order flexural and the first order torsional vibration simultaneously.The pull-in problem caused by the attractive force is avoided,and the friction dissipation can be imaged near the surface.The friction dissipation coefficient concept is proposed and three different contact states are determined from phase and energy dissipation curves.Image contrast is enhanced in the intermediate setpoint region.The work offers an effective method for directly detecting the friction dissipation and high resolution images,which overcomes the disadvantages of existing methods such as contact mode AFM or other contact friction and wear measuring instruments.展开更多
We propose a new analytical approach combining vibrational spectroscopy and acoustic tomography for the detection and characterization of vesicles inside Streptomyces bacteria. Using atomic force microscopy and infrar...We propose a new analytical approach combining vibrational spectroscopy and acoustic tomography for the detection and characterization of vesicles inside Streptomyces bacteria. Using atomic force microscopy and infrared spectroscopy （AFM-IR）, we detect the presence of triglyceride vesicles. Their sizes in depth are measured with high accuracy using mode synthesizing atomic force microscopy （MS-AFM）. We conducted a comparative study of AFM-IR and MS-AFM, and highlighted the advantages of the coupling of these techniques in having a full characterization （chemical, topographical, and volumetric） of a biological sample. With these complementary techniques, a complete access to the vesicle size distribution has been achieved with an accuracy of less than 50 nm. A 3D reconstruction of bacteria showing the in-depth distribution of vesicles is given to underline the great potential of the acoustic method.展开更多
Anticoagulation factor I (ACF I) from the venom of Agki^strodon acutus is a binding protein to activated coagulation factor X (FXa) and possesses marked anticoagulant activity. Single ACF I molecule has been succe...Anticoagulation factor I (ACF I) from the venom of Agki^strodon acutus is a binding protein to activated coagulation factor X (FXa) and possesses marked anticoagulant activity. Single ACF I molecule has been successfully imaged in air by tapping mode atomic force microscopy (AFM) with high resolution using glutaraldehyde as a coupling agent. The physical adsorption and covalent binding of ACF I onto the mica show very different surface topographies. The former exhibits the characteristic strand like structure with much less reproducibility, the latter displays a elliptic granular structure with better reproducibility, which suggests that the stability of ACF I molecules on the mica is enhanced by covalent bonding in the presence of glutaraldehyde. A small scale AFM amplitude mode image clearly shows that the covalently bonded ACF I molecule by glutaraldehyde has olive shape structure with an average size of 7 4 nm×3 6 nm×3 1 nm, which is very similar to the size determined from the crystal structure of ACF I.展开更多
针对原子力显微镜(AFM)在高速扫描下成像误差大的缺点,提出了一种基于压电扫描管动态特性的改进成像方法,并对这种成像方法的性能进行了理论分析和实验验证。分析和实验结果表明,该成像方法可以较好地处理压电扫描管的动态特性,有效地提...针对原子力显微镜(AFM)在高速扫描下成像误差大的缺点,提出了一种基于压电扫描管动态特性的改进成像方法,并对这种成像方法的性能进行了理论分析和实验验证。分析和实验结果表明,该成像方法可以较好地处理压电扫描管的动态特性,有效地提高 AFM 在 Z 方向上的成像精度,因此得到的扫描图像能够更加真实地反映样品的形貌。展开更多
在原子力显微镜(atomic force microscope,AFM)扫描样品时,控制参数调节困难,依赖于操作经验.本文基于在线动态模型辨识,提出了一种AFM系统广义预测自校正控制与成像方法.首先,利用CARIMA(controlled autoregressive and moving-average...在原子力显微镜(atomic force microscope,AFM)扫描样品时,控制参数调节困难,依赖于操作经验.本文基于在线动态模型辨识,提出了一种AFM系统广义预测自校正控制与成像方法.首先,利用CARIMA(controlled autoregressive and moving-average)参数模型来描述局部线性化后的AFM系统模型,并通过在线动态模型辨识得到线性化模型的参数;基于该模型,采用基于GPC(generalized predictive control)的优化方法,在线求解类PI(proportional integral)控制器的参数,进而得到一种具有控制参数自动调整功能的AFM成像方法.为了验证本文方法的有效性,进行了仿真与实验测试.结果表明,在AFM扫描速度不同或PI参数选择不恰当的情况下,该方法能够自动地调整控制器参数,从而减小控制误差,提高成像精度.展开更多
基金Project supported by the National High-Tech Research and Development Program of China (Grant No. 2007AA12Z128)
文摘The periodic impact force induced by tip-sample contact in a tapping mode atomic force microscope （AFM） gives rise to the non-harmonic response of a micro-cantilever. These non-harmonic signals contain the full characteristics of tip-sample interaction. A complete theoretical model describing the dynamical behaviour of tip-sample system was developed in this paper. An analytic formula was introduced to describe the relationship between time-varying tip-sample impact force and tip motion. The theoretical analysis and numerical results both show that the timevarying tip-sample impact force can be reconstructed by recording tip motion. This allows for the reconstruction of the characteristics of the tip-sample force, like contact time and maximum contact force. It can also explain the ability of AFM higher harmonics imaging in mapping stiffness and surface energy variations.
基金financially supported by the Consejo Nacional de Ciencia y Tecnologia (CONACyT) of Mexico (No. 485100-5-38214U)
文摘A standard calibration grating was used for image scanning to investigate the effect of hydration films on imaging resolution by Atomic Force Microscope （AFM）. The results showed that the hydration films greatly affect the imaging resolution for the tapping mode, but no evident effect on the contact mode, The possible reasons for the effect of hydration films on scanning images of AFM are also brought forward here.
基金This research is financially supported by the National Natural Science Foundation of China(No.51527901).
文摘Dynamic friction occurs not only between two contact objects sliding against each other,but also between two relative sliding surfaces several nanometres apart.Many emerging micro-and nano-mechanical systems that promise new applications in sensors or information technology may suffer or benefit from noncontact friction.Herein we demonstrate the distance-dependent friction energy dissipation between the tip and the heterogeneous polymers by the bimodal atomic force microscopy(AFM)method driving the second order flexural and the first order torsional vibration simultaneously.The pull-in problem caused by the attractive force is avoided,and the friction dissipation can be imaged near the surface.The friction dissipation coefficient concept is proposed and three different contact states are determined from phase and energy dissipation curves.Image contrast is enhanced in the intermediate setpoint region.The work offers an effective method for directly detecting the friction dissipation and high resolution images,which overcomes the disadvantages of existing methods such as contact mode AFM or other contact friction and wear measuring instruments.
文摘We propose a new analytical approach combining vibrational spectroscopy and acoustic tomography for the detection and characterization of vesicles inside Streptomyces bacteria. Using atomic force microscopy and infrared spectroscopy （AFM-IR）, we detect the presence of triglyceride vesicles. Their sizes in depth are measured with high accuracy using mode synthesizing atomic force microscopy （MS-AFM）. We conducted a comparative study of AFM-IR and MS-AFM, and highlighted the advantages of the coupling of these techniques in having a full characterization （chemical, topographical, and volumetric） of a biological sample. With these complementary techniques, a complete access to the vesicle size distribution has been achieved with an accuracy of less than 50 nm. A 3D reconstruction of bacteria showing the in-depth distribution of vesicles is given to underline the great potential of the acoustic method.
文摘Anticoagulation factor I (ACF I) from the venom of Agki^strodon acutus is a binding protein to activated coagulation factor X (FXa) and possesses marked anticoagulant activity. Single ACF I molecule has been successfully imaged in air by tapping mode atomic force microscopy (AFM) with high resolution using glutaraldehyde as a coupling agent. The physical adsorption and covalent binding of ACF I onto the mica show very different surface topographies. The former exhibits the characteristic strand like structure with much less reproducibility, the latter displays a elliptic granular structure with better reproducibility, which suggests that the stability of ACF I molecules on the mica is enhanced by covalent bonding in the presence of glutaraldehyde. A small scale AFM amplitude mode image clearly shows that the covalently bonded ACF I molecule by glutaraldehyde has olive shape structure with an average size of 7 4 nm×3 6 nm×3 1 nm, which is very similar to the size determined from the crystal structure of ACF I.
文摘针对原子力显微镜(AFM)在高速扫描下成像误差大的缺点,提出了一种基于压电扫描管动态特性的改进成像方法,并对这种成像方法的性能进行了理论分析和实验验证。分析和实验结果表明,该成像方法可以较好地处理压电扫描管的动态特性,有效地提高 AFM 在 Z 方向上的成像精度,因此得到的扫描图像能够更加真实地反映样品的形貌。
文摘在原子力显微镜(atomic force microscope,AFM)扫描样品时,控制参数调节困难,依赖于操作经验.本文基于在线动态模型辨识,提出了一种AFM系统广义预测自校正控制与成像方法.首先,利用CARIMA(controlled autoregressive and moving-average)参数模型来描述局部线性化后的AFM系统模型,并通过在线动态模型辨识得到线性化模型的参数;基于该模型,采用基于GPC(generalized predictive control)的优化方法,在线求解类PI(proportional integral)控制器的参数,进而得到一种具有控制参数自动调整功能的AFM成像方法.为了验证本文方法的有效性,进行了仿真与实验测试.结果表明,在AFM扫描速度不同或PI参数选择不恰当的情况下,该方法能够自动地调整控制器参数,从而减小控制误差,提高成像精度.
