1050Research on detection and evaluation for blade sharpness of diamond tool based on AFM

Xiaobin Yue

Supervisor: Min Xu

The single point diamond tool is one of the important tools for ultra-precision cutting. Research result shows that nanometer-scale sharpness edge has an important impact on surface quality of ultra-precision machining, in particular, using different sizes of sharpness, it will have a great distinctness on the surface of the workpiece geometry and physical and chemical parameters. Therefore, the edge sharpness of diamond tool is one of the important technical parameters for characterizing its performance. The current study shows that there are two major difficulties on measuring the sharpness of diamond tool: first, conventional contour measuring equipment is not able to measure edge profile effectively, and second, evaluation theory for nanometer-scale edge sharpness of the circular blade diamond tool is not unified.

In this work, based on the analysis of key technology for measuring the edge sharpness of the circular blade diamond tool, we proposed a method for measuring whole edge sharpness and constructed a new type measuring system. In this system, AFM is the main platform, which attached a sophisticated rotary flotation shaft and drive system, to achieve the controllable micro feed of a circular diamond blade in the direction of the edge and multi-point scanning edge parts.

At the same time, the evaluation methods of the edge sharpness of diamond tool were carried out. As we know, the section profile of diamond tool edge is from two straight lines and curves of a class composed of circular, and generally considered the edge sharpness is characterized by edge blunt radius. We used a method based on the second curvature to separate the front and rear flank point and the arc point to be fitted, the results show that the method is simple、fast and accurate. In the meantime, based the least squares method, solution model of blade sharpness was established. Finally, we proposed the evaluation method of whole edge sharpness. Measurement experiments of the edge sharpness were done in this system and results shows that sharpness of tools have a good repeatability.

The cutting experimental results show that the sharpness of the diamond tool is greater than 100nm, the surface roughness Ra of KDP, 2A12, and Copper is greater than 10nm; the sharpness of the diamond tool is 50-70nm, the surface roughness Ra of KDP is less than 5nm, the surface roughness Ra of 2A12 and Copper is less than 10nm. The results illustrate that diamond tool can realize the critical cutting thickness of brittle-ductile transition of brittle material.

References

[1] X.P.Li, M.Rahman, K.Liu, et al. Nano-Precision Measurement of Diamond Tool Edge Radius for wafer Fabrication [J]. Journal of Materials Processing Technology, 2003; 140: 358-362.

[2] Z.Fang, G.X.Zhang. An experimental study of edge radius effect on cutting single crystal silicon[J]. The International Journal of Advanced Manufacturing Technology,2003: 6.

[3]Mingzhou, B.K.A.Ngoi, and X.J.Wang. Tool wear in ultra-Precision diamond cutting of non-ferrous metals with a round-nose tool[J]. Tribology Letters, 2003:15(3):211-216.

[4] C.M. Shakarji. Least-squares Fitting Algorithms of the NIST Algorithm Testing System. Journal of Research of the National Institute of Standardsand Technology. 1998, 103(6): 633~641.

[5] X.S. Zhao, T. Sun, Y.D. Yan, et al. The Measurement of Roundness and Sphericity of the Micro Sphere Based on Atomic Force Microscope. Key Engineering Materials. 2006, 315-316: 796~799

[6] T.H. Fang, W.J. Chang. Effects of AFM-based Nano-machining Process on Aluminum Surface. Journal of Physics and Chemistry of Solids. 2003, 64:913~918

[7] Y.D. Yan, S.Dong and T. Sun. 3D Force Components Measurement in AFM Scratching Tests. Ultramicroscopy. 2005, (105), 62~71

Bidirectional operation of all-normal dispersion fiber lasers

Daojing Li

Supervisor: Deyuan Shen

       Self-started, passively mode-locked erbium-doped soliton fiberlasers as an attractive ultrashort pulse source at the 1.55μmwavelength have been extensively investigated. Among the different passive mode-locking techniques, the nonlinear

polarization rotation (NPR) method has been widely used due to its simplicity and ease of implementation. Conventionally, fiber lasers mode-locked with the NPR method adopt a unidirectional ring cavity. It was shown that such a laser cavity configuration could reduce the spurious cavity reflections and decrease the self-started mode-locking threshold. Indeed, as shown by Tamura et al based on a mode-locked fiber laser and a solid-state laser, significant threshold power reduction could be achieved with a unidirectional ring cavity than a linear cavity. In the early days of the fiber laser development, due to the lack of a high power pump source, reduction of the laser mode-locking threshold is necessary. In 2006, Zhao et al reported self-started unidirectional operation of afiber ring soliton laser without an isolator. The laser operated in net anomalous dispersion regime.

       In this work, we report bidirectional operation of an all-normal-dispersion Yb-doped fiber laser mode-locked by the nonlinear polarization rotation (NPR) technique but without an isolator in cavity. It has been shown that a unidirectional ring cavity could reduce the spurious cavity reflections and thus decrease the self-started mode-locking threshold. Due to the lack of a high power pump source, traditionally, fiber lasers mode-locked by the NPR technique adopt a unidirectional ring cavity. In the paper, we show experimentally that one could also obtain NPR mode locking and dissipative soliton operation in an all-normal dispersion bidirectional fiber ring laser. Both the unidirectional operation and bidirectional operation are studied. An isolator was first inserted in the cavity to force unidirectional operation, then the isolator was removed for bidirectional operation. Apart from the dissipative soliton operation, noise-like pulses are achieved by carefully adjusting the intra-cavity polarization. The bandwidth of the noise-like pulses is up to 60 nm, which is much broader than the gain bandwidth of Yb-doped fiber (~40nm).

References

[1]  Richardson D J, Laming R I, Payne D N, et al. Electronics Letters, 1991, 27(9): 730-732.

[2] Tamura K, Jacobson J, Ippen E P, et al. Optics letters, 1993, 18(3): 220-222.

[3]  Tamura K, Ippen E P, Haus H A, et al. Optics letters, 1993, 18(13): 1080-1082.

[4]  Zhao L M, Tang D Y, Cheng T H, et al. Journal of Optics A: Pure and Applied Optics, 2007, 9(5): 477.

High-Throughput screening of Microarrays with Label-Free OI-RD microscope

Chenggang Zhu

Supervisor: YiyanFei

       Microarrays of biological molecules immobilized on functionalized solid surface are widely used to research 100-100,000 biochemical reactions^[1], such as protein-ligand interactions^[2]. This technique complements the deficiency of conventional biochemistry that can only study a few reactions one time. In this research field, Fluorescence microscopy is widely employed to characterize reaction end-points in microarrays due to its sensitivity and availability. However, some extrinsic tag, such as fluorescent molecules or quantum may change or even eliminate the properties of host biological molecule, which is detrimental to kinetics process measurements. So label-free optical biosensors, such as surface plasmoresonance(SPR) based biosensors, are often used to monitor the kinetics process. However, most of these biosensors are limited by their low throughput (2-10 parallel reactions) and require the molecules to be deposited on some special substrates (e.g. gold films for SPR biosensors). Additionally, a notable challenge is the development of reliable, efficient methods to attach small molecules on solid surfaces. So, it is desirable to develop a label-free optical detection methodology for high-through put detection of small-molecule protein interactions in microarray format and relevant combinations of surface immobilization strategy.

Based on the theory of oblique-incidence optical reflectivity difference (OI-RD),we developed ascanning optical microscopeto perform real-time and end-point detection of reactions occurring in biomolecular microarrays with over 10,000distinct immobilized targets on a single functionalized glass slideand its sensitivity is comparable to SPR biosensors^[3]. Asurface morphology change such as protein binding reactions with a target alters the ratio of the Fresnel reflection coefficientsrp/rs = tanψexp(iδ).OI-RD microscopes detect reactions by ellipsometrically measuring changes in the ratio of the Fresnel reflection coefficients at an oblique angle of incidence. For surface mass density of an optically thin non-absorbing layer on a transparent substrate，only the changes in phase, Δδ is significant. And our OI-RD microscope directly measures the change in δ. Meanwhile, we adopt a robust method for the covalent capture of small molecules with diverse reactive functional groups in microarray format^[4]. And avaporcatalyzed, is ocyanate-mediated surface immobilization scheme is used to attach bioactive small molecules like biotin molecule with different functional groups, such as hydroxyl, carboxyl, amino and so on. And then, we probed the joint efficiency by the OI-RD microscope. What’s more, we research the influences of isocyanate-medium with different longitudinal PEG linker to the joint efficiency.

References

[1]Zhu, H., M. Bilgin, R. Bangham, et al. “Global analysis of protein activities using proteom chips,” Science 293, 2101-2105 (2001).

[2] X.D. Zhu, J.P. Landry, Y.S. Shun, J.P. Gregg. K.S. Lam, X.W. Guo, “Oblique incidence reflectivity difference microscope for label-free high- throughput detection of biochemical reactions in a microarray format,” Appl. Opt. 46, 1890-1895 (2007).

[3]Zhu, X., J.P. Landry, Y.S. Sun, et al., “Oblique-incidence reflectivity difference microscope for label-free high-throughput detection of biochemical reactions in a microarray format,” Applied Optics 46, 1890-1895 (2007).

[4] James E Bradner, Olivia M McPherson,and Angela N Koehler,” A method for the covalent capture and screening ofdiverse small molecules in a microarray format”, Protocol 282,2344-2352(2006).

Time:  6:30 pm, Thursday, 2013.10.23

Location: Optical Building. Room 525