A wall-jet ring disk electrode fabricated within a thin-layered micromachined cell

The wall-jet ring disk electrode (WJRDE) has been used with a thin layer ce ll in a flow system. Usually, the cavity for the solution flow and reaction s on the ring disk electrode (RDE) is formed with an elastomer spacer. Acco rdingly, the thickness is more than several tenths of a micrometer. If a ve ry thin-layered WJRDE (TLWJRDE) is fabricated, the collection efficiency N, which indicates the rate at which the product on the disk is captured onto the ring electrode, is expected to increase. Therefore, a TLWJRDE was prep ared in a very thin cavity and was fabricated by micromachining. Ditches an d the cavity were formed on a glass plate by photolithography and chemical etching. and this chip was pasted onto another glass substrate prepared wit h the RDE on it. The sample solution was introduced from the center of the device, and was spread over the electrodes. After this, it went out from th e periphery of the device. The TLWJRDE was evaluated using the Fe(CN)(6)(4- /3-) redox system, and its characteristics are discussed. When the flow rat e was decreased, N increased to nearly 100%. This tendency was stronger, es pecially when the flow-through cell was thinner. Compared to other RDEs rep orted previously, a very thin cavity of micrometer order can be fabricated, and large N values were obtained in the TLWJRDE system. The TLWJRDE can be manufactured by micromachining and is expected to be used as a disposable detector. (C) 1999 Elsevier Science S.A. All rights reserved.