Exploring FET Concepts for Lab-on-a-Chip

Abstract

The intial aim of the ISFET application in the 1970s was to construct a new tool for electrophysiological experiments, but unfortunately, this has never been taken up by the medical field. However, in view of recent experimental results of stimulus-response measurements with protein-covered ISFETs, it may be useful to redo the original measurements. This may result in a lab-on-a-chip for dynamic cell acidification measurements.

From the history of ISFET development, the combination of an ISFET with a pH actuator may be considered as a remarkable achievement. In the first place because it delivered factually the first lab-on-a-chip device and secondly because it can serve as the start of a new type of electrophoretic device for protein separation while simultaneous monitoring of the degree of separation.

Two dimensional ISFET arrays may not fulfill the requirements of measuring many samples in parallel or in series as needed in present lab-on-a-chip devices, due to spatial limitations. A solution may be to apply the read-out concept as used in the presently being developed SeeMOS technology for optical cameras. In stead of photons, the (bio) molecular events at the surface may induce the charges or currents in the sensing MOS structure, or directly, or by means of an ion controlled diode.

The field effect concept can not only be used for the measurement of double layer phenomena at insulator/electrolyte interfaces, but also for manipulation of the double layer and by this for flow modulation, on which effect the so-called FlowFET is based. This control concept may be extended by applying specific electrode configurations and voltage profiles.

Combining flow control and detection in one and the same device may ultimately lead to a lab-on-a-chip design in which all components rely on the FET concept.