| Research Abstract |
We developed a high-resolution scanning electrochemical microscope (SECM) towards characterization of various micro-bio devices. Our SECM-based multifunctional measuring system provides near-field scanning optical microscopic (NSOM) information by featuring an optical fiber-electrode probe. The size of the electrode-, optical fiber-, or optical fiber-electrode- probe is less than 100nm, which allows us high-resolution images of protein arrays and cellular arrays. The feedback mechanism controlling the probe-sample distance is based on the shearing force, by which high-quality images of rough surfaces with the height differences larger than 10μm and fragile samples such as living cells under physiological conditions were captured.
1, Nano-electrode probes were fabricated with the Ti/P sputtering and the subsequent parylene C-vapor deposition polymerization. The effective electrode radius estimated from the cyclic voltammogram for ferrocyanide has found to be less than 50nm. The optical f
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iber-electrode probes with the radii less than 100nm were made as the same manner. The optical aperture size was also less than 100 nm which was confirmed from the cross section of the NSOM image of the quantum-dot (QD) particles with tens nm-diameters.
2, The feedback mechanism controlling the probe-sample distance was improved by vertically moving the probe with the width of 〜 100nm to reduce the damage applied to the samples. This feedback mode, defined as "standing approach (STA) mode" (Yamada et al., Anal. Chem., 2005, 77, 1785-179), has allowed to simultaneous electrochemical and topographic images of the axon and the cell body of the single PC-12 cell under physiological conditions for the first time. The STA-mode feedback imaging sometimes works better than the tip-sample regulation for the commercially available AFM. For example, relatively larger polystyrene beads (with 〜 10μm diameter) can be imaged with our STA-mode SECM, whereas not imaged with the conventional AFM instrument.
3, Towards the progress in the construction of the micro-bio devices, various techniques to pattern baiomaterials were attempted. Especially, collagen-gel embedded culture of bacteria and mammalian cells with ultra-small volume (tens to several nL) has been successfully demonstrated on glass or silicon chip to microfabricate various types of cellular arrays. Micro-contact printing (μCP), microfluidics, dip-pen nanolithography (DPN), and negative dielectric phoresis (n-DEP) have been also applied to assemble protein and cellular arrays. Less
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