Metal Deposition Deep into Microstructure by Electroless Plating

Abstract

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...

Multi-channel SPR biosensor based on PCF for multi-analyte sensing applications

“…The thin gold layer on the inner surfaces of the micro fluidic slots can be achieved using high pressure chemical vapour technique [10]. Alternatively, electrolytic plating can be used to deposit the required amount of gold [11,12].…”

“…As there is an absence of a flow cell system, the cross sectional area of the micro fluidic channels would be no concern as moving sample volumes within a time frame at a given pressure won't be required. High pressure chemical vapor technique is one efficient way to apply gold depositions on the inner surfaces of the micro fluidic slots [10]. Both gold and the metal oxide are chemically stable and are relatively easy to come by.…”

“…These fibers can have channels included in their construction in which the gold layers can be applied and the analyte can be accommodated [10,11]. Their fluidic design capabilities are highly beneficial in applications where volatile or toxic samples are used.…”

A Novel Compact Photonic Crystal Fibre Surface Plasmon Resonance Biosensor for an Aqueous Environment

“…Deposition of metal layers inside of the micro fluidic slots can be performed either with the high-pressure chemical vapor deposition technique (Sazio 2006) or electroless plating techniques used in fabrication of metalized hollow waveguides and microstructures (Harrington 2000;Takeyasu, Tanaka, and Kawata 2005).…”

“…Deposition of metal layers inside of the micro fluidic slots can be performed either with the high-pressure chemical vapour deposition technique (Sazio 2006) or electroless plating techniques used in fabrication of metalized hollow waveguides and microstructures (Harrington 2000;Takeyasu, Tanaka, and Kawata 2005). A full -vectorial Finite Element Method (FEM) with perfectly matched layers (PML) is employed to investigate the variation of key performance parameters such as sensitivity and www.intechopen.com confinement losses with structural parameters such as air hole diameter and gold thickness in the next section of the chapter, followed by conclusion in the final section.…”