A Micromachined Kelvin Probe for Surface Potential Measurements in Microfluidic Channels and Solid-State Applications

This paper reports on a micromachined Kelvin probe structure with integrated scanning tip and dither actuation mechanism. It is fabricated by a modified micro electro-discharge machining process which allows electrical isolation within the micromachined structure using epoxy plugs. The device is used to measure changes in the external surface potential of a parylene microfluidic channel as a function of varying pH of liquid inside the channel. A contact potential difference of $=6{\rm V}$ is measured for a change in pH from 4 to 8 within the channel. The device is also used to map embedded charge in a thin SiO2 layer on a Si substrate, showing it to be suitable for monitoring microelectronics manufacturing processes.