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

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.