Design of an a-Si:H Interface Circuit for Liquid Crystal Chemical and Biological Sensor Array

Abstract

In this paper an interface circuit has been designed using hydrogenated amorphous silicon (a-Si:H) thin film transistors for array of capacitive liquid crystal (LC) chemical and bio- logical sensors. Amorphous silicon has high uniformity over large area electronics and has relatively low cost fabrication process. The proposed circuit is insensitive to a-Si:H non-ideal behavior such as low mobility and threshold voltage change. The circuit provides analog input interface and has direct digital output while consuming 0.02 mm2 of chip area and 35 μW of power. More than 200 000 sensor units can be fabricated on a chip area as small as an iPad display. To the knowledge of the authors, this is the first a-Si:H interface circuit for capacitive LC chemical and biological sensor.