Dual-cylinder microelectrodes. Part 1.—Theoretical consideration of the steady-state current

Abstract

The feedback diffusion current at a dual-cylinder microelectrode was modelled for the case of steady-state response using bilinear transformation of coordinates in the diffusion space. The model outlined assumes that lines of mass flux and concentration are represented by orthogonal circular functions. An expression for the diffusion current is presented which draws attention to the importance of device geometry, anode and cathode radii, and interelectrode distance. The theoretical treatment shows that significant current amplification can only be expected for a dual-cylinder device over a single-cylinder microelectrode when interelectrode gap reduces to the submicrometer dimension. The practical limitations of the diffusion current equation are discussed in the context of general diffusion theory for feedback devices.