Development of an Impedance Analyser with Complex Capacitance for Biosensing Applications

Capacitive biosensors have shown promise in detecting surface modifications and changes in analyte as a result of biological events on a transducer surface. The development of an impedance analyser with complex capacitance analysis that has been tailored to low frequency biosensing applications using gold interdigitated electrodes, is discussed in this paper. The designed device bridges the gap between expensive and complex analysers that are used for research, and a simple device that can directly compute complex capacitance and can be used in pointof-care environments. The device was calibrated, and results validated against the PalmSens4. Impedance and capacitance spectroscopy tests were run comparing different dilutions of phosphate buffered saline. The complex capacitance computation showed an error of 1.222% and 0.656% for the real and imaginary components respectively. The designed impedance analyser successfully differentiated between changes in concentration of phosphate buffered saline, and therefore has potential for use in the detection of various proteins.