Single chip solution to capacitive liquid crystal chemical and biological sensor

In this paper a CMOS single chip capacitive liquid crystal chemical and biological sensor is presented. Two on-chip interdigitated capacitors provide differential sensor measurement. The system consists of a low noise preamplifier, synchronous demodulator and low pass filter. For high sensitivity detection proper excitation signal voltage and frequency have been investigated and the preamplifier noise has been minimized using a nonlinear optimization algorithm. To the knowledge of the authors this is the first integrated capacitive liquid crystal chemical and biological sensor chip. The amplifier has 15aF resolution with 1kHz bandwidth and consumes 1mW of power and 0.4mm2 of chip area using AMI 0.5µm technology.