A Core-CBCM sigma delta capacitive sensor array dedicated to lab-on-chip applications

A sigma delta (Sigma Delta) capacitive sensor is presented in this paper for highly integrated lab-on-chip (LoC) applications using charge based capacitance measurement method (CBCM). We put forward the design and implementation of sensor chip in 0.18 mu m CMOS process featuring an array of capacitive sensors, an offset cancellation (OC) circuitry and a DC input first-order Sigma Delta analog to digital converter (ADC). This sensor chip is incorporated with a microfluidic channel using direct-write fabrication process. The design, construction and experimental results are demonstrated using chemical solvents with known dielectric constants and polyelectrolyte solutions in order to show the viability of the proposed capacitive sensor for LoCs. (C) 2008 Elsevier B.V. All rights reserved.