communications Figure 6. a) SEM image of the free-standing silver pillar on the cover slip, made by using a laser power of 1.14 mW and a linear scanning speed of 3 mm s À1 , taken at an observation angle of 45 8. The inset is a close-up view of the silver pillar parallel to the substrate, which demonstrates the linewidth of the smallest portion of the silver pillar as 180 nm. b) SEM image of silver pyramids, fabricated with a laser power of 1.3 mW and scanning speed of 2.5 mm s À1 , taken at an observation angle of 45 8. The inset on the left is a top view of the silver-pyramid array. The inset on the right is a close-up view of the silver pyramid.

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The lateral spatial resolution (LSR) in two-photon induced polymerization was improved to 80nm by using an anthracene derivative (9,10-bis-pentyloxy-2,7-bis[2-(4-dimethylamino-phenyl)-vinyl]anthracene (BPDPA)) as a highly sensitive and efficient photoinitiator. Photocurable resin containing 0.18mol% BPDPA exhibited a low polymerization threshold of 0.64mW at 800nm. Theoretical calculations showed that the LSR can be increased by reducing the laser power, indicating that the LSR could be improved using more sensitive initiators in the future.

An experimental protocol for the realization of three-dimensional periodic metallic micro/nanostructures over large areas is presented. Simultaneous fabrication of hundreds of three-dimensional complex polymer structures is achieved using a two-photon photopolymerization (TPP) technique combined with a microlens array. Metallization of the structures is performed through the deposition of thin and highly conductive films by electroless plating. A chemical modification of the photopolymerizable resin and the production of a hydrophobic coating on the glass surface supporting the structures are realized. This process prevents metal deposition on the substrate and restricts adhesion on polymer. Our technique can produce periodic and/or isolated metallic structures with arbitrary shape, created by more than 700 individual objects written in parallel.

We report on selective metal deposition over complex polymer structures formed by two-photon induced photopolymerization technique. Periodic three-dimensional micro/nanostructures are fabricated by means of a microlens array to produce multiple spots from a single-beam femtosecond laser. An electroless plating method is used to deposit a thin silver film onto the sample surface. The glass slide surface supporting the structures is chemically modified to avoid silver coating of the substrate. Our technique enables to produce complex metallic structures with arbitrary shapes under ambient conditions.

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It is generally difficult to deposit metal on an occluded part of a structure or inside a long tubular structure. In this paper, we report an electroless plating method that is useful for metal deposition onto internal obscured regions of a complex structure, and we show that the technique can deposit metal over a wide area. We demonstrate gold deposition inside a capillary tube and a complex concave structure of micrometer scale consisting of polystyrene microbeads sandwiched between glass plates.Metal microfabrication has been actively studied and used in various fields because of the unique optical, electrical, and catalytic properties of the fine structures that it can produce. [1][2][3][4][5][6] The ability to simultaneously and precisely fabricate a number of micro-objects over a wide region is essential to the practical application of nanotechnology. In these processes, plating methods are occasionally used for metal deposition. Plating is a conventional method of depositing metal onto substrates, 7) and can be used not only with conductors, but also with insulators such as plastics and ceramics. Among known plating techniques, electroless plating is commonly used for metal deposition on insulators because it does not require any external electric field. Electroless plating is chemically performed with a solution, and it results in a uniform metal deposition over the entire surface area of micro-objects. 8-10) With this method, it is possible to deposit metal effectively even though the area is limited to less than a micrometer in width. 11,12) Moreover, a number of micrometer-scale metal patterns can be fabricated simultaneously over a very wide area much more easily than with sputtering or vacuum evaporation, which require large, complex equipment. These techniques have been long studied, and are used widely for metal fabrication processes. However, it is generally very difficult, using these methods, to deposit metal on a deep or normally occluded part of a structure, such as the inner wall of a long tubular structure.In this letter, we demonstrate electroless plating on three types of structure. First, gold was deposited on the inner wall of a fused-silica capillary, which is difficult to achieve by other methods. Second, silver was deposited onto glass beads. Third, gold was deposited inside a complex concave structure formed by polystyrene microbeads sandwiched between glass plates.As mentioned above, although it is generally difficult to coat metals onto the inside of a concave structure using other methods (such as vacuum evaporation and sputtering), with electroless plating the plating solution containing metal ions naturally goes into the inside of even a fine, complex structure, and therefore all surfaces contacting the plating solution are uniformly coated with metal.To determine the main features of our process and to verify its effectiveness, we first investigated the relationship between the amount of gold deposited onto the surface of a polystyrene substrate at room temperature (295 K) by m...

Noble metallic nanosurface exhibits both plasmonic and catalytic functions. Surface-enhanced Raman scattering of para-aminothiophenol (p-ATP) was measured on a highly uniform two-dimensional silver nanoparticle array at different intensities of an excitation laser (532 nm) ranging from 4 to 4000 W/mm 2 . It was observed that p-ATP was chemically transformed to 4,4′-dimercaptoazobenzene (DMAB) with the laser intensities of ≥40 W/mm 2 during the Raman measurement. At 4 W/mm 2 , the Raman peaks of DMAB disappeared, which indicates that the laser intensity was insufficient for the chemical transformation although it was sufficient for the Raman measurement. The highly uniform silver nanoparticle array allowed quantitative analysis on the Raman peak intensity. The threshold of the chemical transformation from p-ATP to DMAB was estimated to be ∼18.8 W/mm 2 on the silver nanoparticle array whose enhancement factor is ∼10 4 .