Developing a miniaturized continuous flow electrochemical cell for biosensor applications M. Ilie* a,b , E. Ovreiu b , R. Dejana a , V. Foglietti a , L. Nardı c , A. Mascı c , B. Lanza d , L. Della Seta c , M-R. Montereali c , W. Vastarella c , R. Pılloton c a CNR/IFN, Via Cineto Romano 42, Rome, Italy b Univ. Politehnica Bucuresti, LAPI, Bd Iuliu Maniu 1-3, cam 135, 161071 Bucharest, Romania c ENEA, SP 061,C.R. Casaccia, Via Anguillarese 301, 00060 Santa Maria di Galeria, Rome, Italy d ENEA, C.R. Portici, Via Vecchio Macello 80055, Portici (Napoli), Italy ABSTRACT The development of a miniaturized electrochemical cell for biosensor application regards both the structuring of an array of electrodes in a fluidic chamber and their connections to the control & processing unit The sensitivity of the chrono- amperometric measurement performed with the cell is increased by: (a) integrating the reference electrode on the same chip with the counter- and working- electrodes, (b) designing a specific pattern of the gold electrodes and (c) serially distributing them along the pipeline reservoir. Borosilicate glass is used as substrate for the electrodes, allowing, due to its transparency, an accurate and easy pad to pad alignment of the up-side-down chip versus a PCB soldered on a standard DIL 40 socket. This alignment is necessary to accomplish the elastomer-based-solderless electric contact, between chip and PCB. The solderless contact significantly improves both reliability and signal processing accuracy. The reservoir and its cover are micromachined out of silicone rubber respectively photosensitive glass in order to easy disassemble the fluidic chamber without any damage. Both thickness and elasticity of the photosensitive glass rend the device less brittle. A plug-in -plug-flow device with improved characteristics has been obtained with a modular structure that allows further extension of the number of electrodes. Keywords: electrochemical cell, electrodes array, chronoamperometric measurements, fluidic chamber 1. INTRODUCTION The biosensors, as functional analogs of chemoreceptors, are based on the direct spatial coupling of immobilized biologically active molecules with a signal transducer and an electronic amplifier. They use biological systems at different levels of integration to specifically recognize the substance to be determined (the analyte). The first step of this recognition is the specific complex formation by interaction of the immobilized biologically active molecules with the studied substance. The physicochemical changes caused either by the complex formation or by the chemical conversion of the analyte (e.g. owing to enzymes) might be of electrical nature (charge or enzyme activity) and therefore they can be indicated by means of transducers, based on potentiometric or amperometric electrodes, that perform the second step of the recognition: transduction of the physicochemical effect into an electrical signal. In this way species as H + , OH - , CO 2 , NH 3 , H 2 O 2 can be identified in a so-called electrochemical biosensor. Further on, the electric signal has to be amplified and processed. The electrochemical indication prevails over all other methods of transduction [1]. Screen-printed electrodes are widely used as transducers in electrochemical biosensors [2]. The miniaturization of the electrodes using techniques borrowed from the semiconductor industry and their integration in a continuous flow micro-cell opens wide and interesting perspectives for the development of biosensors, offering the possibility to increase both the speed and the sensitivity of detection. Such a micro-cell, working in continuous flow, has been previously approached by the authors [3]. Its functional tests have revealed some characteristics that should be improved: (a) electrode behavior (sensitivity), (b) the reliability of both electric and fluidic connections (c) alignment accuracy. The causes of these drawbacks have been analyzed and new technical solutions have been adopted as follows. 2. EXPERIMENTAL RESULTS The electrochemical biosensor micro-cell consists of a set of working electrodes (WE), a counter-electrode (CE), and a reference electrode (RE) placed inside a reservoir provided with inlet and outlet openings for the fluid flow. Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies IV, edited by Paul Schiopu, Cornel Panait, George Caruntu, Adrian Manea, Proc. of SPIE Vol. 7297, 729724 · © 2009 SPIE CCC code: 0277-786X/09/$18 · doi: 10.1117/12.823688 Proc. of SPIE Vol. 7297 729724-1