Chemical diversity in electrochemically deposited conducting polymer-based sensor arrays

• We demonstrate increased chemical-diversity in conducting polymer sensor arrays.
• The role of dopant on chemical sensitivity is demonstrated.
• The polymer's oxidation state can also be used to tune chemical sensitivity.
• Varying these conditions increases diversity of a polymer by an order of magnitude.

The mammalian olfactory system is highly complex, with more than 1000 non-specific binding receptors. The chemical diversity among these receptors yields differential responses resulting in a ‘fingerprint’ response pattern characteristic of a particular gas phase odorant or mixture. It is through these response-patterns that our brain perceives its chemical environment. While the concept of an electronic nose has been explored over the past several decades, the emergence of integrated circuits analogous to charge-coupled device (CCD) devices with this kind of chemical sensitivity have yet to emerge. One of the main stumbling blocks is the ability to deposit large numbers of chemically diverse sensing layers within large-scale integrated circuits. The use of electronically conducting polymers (ECP) as sensing layers are attractive since they can be electrodeposited on existing fabricated structures without the need for additional lithographic steps, however they are limited by the number of chemically different monomer units available. In this study, we demonstrate the ability to significantly increase the level of diversity through the control of the dopant and the oxidation level of the deposited polymer layers. By using two polymers, several dopants and different oxidation states determined by applied electrochemical potential, fifty-five chemically diverse sensing elements are produced. These results suggest that by using these orthogonal variables, a chemically diverse integrated sensor array chip can be generated through a combinatorial approach of deposition conditions.