It has been discovered that ionic liquid can be observed by a scanning electron microscope without accumulation of electron charges, allowing SEM observation of insulating specimens wetted with ionic liquid.

Underpotential deposition (UPD) of Ag on Au(111)/mica electrodes coated with a self-assembled monolayer (SAM) of propanethiol or octanethiol and reductive desorption of the SAM after conducting UPD have been studied using voltammetry, XPS measurement, and scanning tunneling microscopy (STM). The reductive desorption potential of the SAM was changed by UPD of Ag from a characteristic value obtained at Au to that at Ag, indicating that the UPD of Ag took place through the SAM layer in such a way as to intervene between the SAM and the Au electrode. No significant loss of thiol molecules occurred during the Ag deposition. The rate of UPD through the SAM of propanethiol was so fast as to be completed within 10 s, while that for the SAM of octanethiol took ca. 50 min or more to build up the SAM/Ag/Au structure. Voltammetric results indicated that the UPD of Ag proceeded initially at molecular defects in the SAM of octanethiol and that the resulting Ag islands grew laterally to limiting coverage. Ex situ STM observations showed clearly the presence of such Ag islands on terraces of the Au(111) electrode surface.

No abstract

The nature of an albumin-coated substrate that blocks protein adsorption and cell adhesion was rapidly switched to cell-adhesive by exposure to an oxidizing agent such as HBrO. This finding has enabled cellular pattern drawing even on a single-cell level by closely scanning a microelectrode above the substrate and electrochemically producing the agent at the tip of the electrode. The present microelectrochemical cell patterning is applicable even for a previously cell-patterned substrate and for a grooved substrate. These unique technical features will have impacts on a variety of cell-based studies that require the analysis of heterotypic cell-cell interactions and cellular arrangement on an uneven surface such as semiconductor devices.

Two-dimensional micropatterns of microparticles were fabricated on glass substrates with negative dielectrophoretic force, and the patterned microparticles were covalently bound on the substrate via cross-linking agents. The line and grid patterns of microparticles were prepared using the repulsive force of negative dielectrophoresis (n-DEP). The template interdigitated microband array (IDA) electrodes (width and gap 50 mum) were incorporated into the dielectrophoretic patterning cell with a fluidic channel. The microstructures on the glass substrates with amino or sulfhydryl groups were immobilized with the cross-linking agents disuccinimidyl suberate (DSS) and m-maleimidobenzoyl-N-hydroxy-succinimide ester (MBS). Diaphorase (Dp), a flavoenzyme, was selectively attached on the patterned microparticles using the maleimide groups of MBS. The enzyme activity on the patterned particles was electrochemically characterized with a scanning electrochemical microscope (SECM) in the presence of NADH and ferrocenylmethanol as a redox mediator. The SECM images proved that Dp was selectively immobilized onto the surface of microparticles to maintain its catalytic activity.