Fabrication of Integrated Microelectrodes for Electrochemical Detection on Electrophoresis Microchip by Electroless Deposition and Micromolding in Capillary Technique

Abstract

A new method for the fabrication of an integrated microelectrode for electrochemical detection (ECD) on an electrophoresis microchip is described. The pattern of the microelectrode was directly made on the surface of a microscope slide through an electroless deposition procedure. The surface of the slide was first selectively coated with a thin layer of sodium silicate through a micromolding in capillary technique provided by a poly(dimethylsiloxane) (PDMS) microchannel; this left a rough patterned area for the anchoring of catalytic particles. A metal layer was deposited on the pattern guided by these catalytic particles and was used as the working electrode. Factors influencing the fabrication procedure were discussed. The whole chip was built by reversibly sealing the slide to another PDMS layer with electrophoresis microchannels at room temperature. This approach eliminates the need of clean room facilities and expensive apparatus such as for vacuum deposition or sputtering and makes it possible to produce patterned electrodes suitable for ECD on microchip under ordinary chemistry laboratory conditions. Also once the micropattern is ready, it allows the researchers to rebuild the electrode in a short period of time when an electrode failure occurs. Copper and gold microelectrodes were fabricated by this technique. Glucose, dopamine, and catechol as model analytes were tested.

An end-channel amperometric detector for microchip capillary electrophoresis

“…The sensitivities of 47.3 and 20.6 pA/M were obtained for DA and CA, respectively. By measuring 5 m DA alone with the same condition, the limit of detection (LOD) of DA was 0.51 m (S/N = 3), which was more sensitive than some works [22,23,25] while higher than reference [16,19,26]. The bigger electrode diameter thus the bigger background (about 20 pA in this work versus 1.6 pA in reference [17]) may partly explain the higher LOD, incomplete decoupling (0.1 V higher detection potential implied) of detection circuit may be another reason.…”

“…RSDs of peak currents (i RSD ) were 5.4 and 6.0% for DA and CA respectively, which were better than reference [23] and some what worse than [19,22]. Although migration times of DA and CA were fast (<80 s), RSDs of migration times (t RSD ) of DA and CA were better compared with reference [22] and slightly better than reference [24]. Furthermore, electrophoresis operation was carried out manually in this work, so the reproducibility seemed good.…”

Controllable alignment of elongated microorganisms in 3D microspace using electrofluidic devices manufactured by hybrid femtosecond laser microfabrication

“…Then, stirring copper plating was carried out at the same temperatures for 1-10 h after replacing the solution with a new solution. Finally, stirring gold plating was performed at 85-90°C for 1-12 h. The two-step electroless plating process enables high selectivity in metal deposition 36,37,39,40 . Figure 1d shows magnified images of regions I-IV in Figure 1b (from left to right).…”

A Capillary Electrochromatographic Microchip Packed with Self-Assembly Colloidal Carboxylic Silica Beads

“…To prevent erosion of the packing structure at each entrance of microchannels resulting from the exposure to buffer solution or sudden polarity change of driving voltage, the packing at the entrances was fixed by the electroless silver-plating technique. 18,19 After filling the microchannels and reservoirs with 10 mM phosphate buffer solution (pH 7), the microchips were left to stabilize overnight. After removing the buffer solutions from the reservoirs, each reservoir was filled with a drop of 0.1% SnCl 2 , and allowed to stand for 30 sec.…”