sensoring
Polymer-based Capacitive
Sensor for Detection of
Organic Water Pollutants
Wetsus, centre of excellence for sustainable water technology
P.O. Box 1113, 8900 CC Leeuwarden, the Netherlands
Judith Staginus
[email protected]
Motivation
The resources of high quality water suitable for drinking purpose and industrial
uses are getting scarce. Monitoring of toxic organic pollutants at trace level
and in different chemical speciation requires sophisticated smart sensor
systems. The goal of this project is the development of an online, label-free,
capacitive chemical sensor that establishes a fingerprint of the water quality
by means of a chemically diverse multi-array.
Technological challenge
A popular sensor platform is the interdigitated electrode (IDE) design as
shown in the insertion of Fig. 1. The polymer is usually spin-coated onto the
IDE structure to form the chemical sensing layer of desired thickness (h).
The concentration of the pollutant in the water (CW) and
in the polymer (CP) is predicted by the partition coefficient
log P:
⎛ CP ⎞
log P = log ⎜
⎟
⎝ CW ⎠
The change in capacitance of the polymer layer is related
to adsorption and absorption of the pollutant but also to
swelling (∆h) (Fig. 1).
Fig. 1 Schematic representation of the sensor response processes
A multi-array of sensors with divers polymer layers provides the necessary chemical diversity to identify and quantify
pollutants by means of multi-component analysis (MCA) tools and pattern recognition techniques (PRT) (Fig. 2).
The technological challenges lie in the development of insulating (mono-)layers to prevent leakage currents and the
synthesis of chemically resistive polymeric sensing layers to guarantee reliable and stable sensor responses in the
aqueous environment.
multi-array sensor
electronic readout/signal conditioning
algorithmic software
Fig. 2 Schematic representation of the system components of a multi-array sensor
Also, the choice of the calibration design and algorithmic software for the interpretation of the multivariate sensor
response is crucial. Therefore, the development of this sensor requires a full system-based approach.
www.wetsus.nl
Dr. ir. L.C.P.M de Smet, Prof. Dr. E.J.R. Sudhölter, Dr. H. Miedema
www.tudelft.nl