An Integrated Low-Power and Small-Area Time-Domain Dielectric Chip Sensor

Abstract

We presented a novel integrated dielectric chip sensor based on time-domain sensing technique. The sensor is based on a dielectric constant-dependent delay line with a load capacitor realized by an interdigitated capacitor (IDC). The IDC exposed to the material under test (MUT) is used to sense the change of MUT’s dielectric constant. The delay line is utilized to generate a delay proportional to the measured dielectric constant. To improve the sensitivity with a smaller area, a time-amplifier (TA) is employed to amplify the delay change. As a proof of concept, the sensor has been calibrated with Ethyl-acetate, Butyraldehyde, Isopropanol and Ethanol. Ethanol and Ethyl-acetate mixture solutions, in steps of 20% of concentration change, have been used to demonstrate the performance of the sensor. The chip is fabricated in a 55 nm CMOS technology with a core area of 0.105 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> mm. It only consumes 0.13 mA from a single 1.2 V. Compared with other methods, this method has more advantages in sensor array applications.