Boisen, Anja

Fischer, Lee MacKenzie

Quan, Xueling

Tenje, Maria

Online Research Database In Technology

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Downloaded from orbit.dtu.dk on: Dec 19, 2017Investigation of Electrochemical and Mechanical Behaviour of ElectrochemicalCantilever Sensor by Electrochemical methodsQuan, Xueling; Fischer, Lee MacKenzie; Boisen, Anja; Tenje, MariaPublished in:ProceedingsPublication date:2011Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Quan, X., Fischer, L. M., Boisen, A., & Tenje, M. (2011). Investigation of Electrochemical and MechanicalBehaviour of Electrochemical Cantilever Sensor by Electrochemical methods. In Proceedings (Vol. Paper No.196)Proceedings of the 2nd International Conference on Nanotechnology: Fundamentals and Applications Ottawa, Ontario, Canada, 27-29 July 2011 Paper No. 196 196-1  Investigation of Electrochemical and Mechanical Behaviour of Electrochemical Cantilever Sensor by Electrochemical methods Xueling Quan, Lee M. Fischer, Anja Boisen, Maria Tenje  Technical University of Denmark, DTU Nanotech – Department of Micro- and Nanotechnology, Building 345 East, DK-2800 Kongens Lyngby, Denmark Email: xueling.quan@nanotech.dtu.dk  KEYWORDS: Electrochemical cantilever, surface stress, chemical sensor, amperometry  1 INTRODUCTION Microcantilevers show great potential for use as chemical sensors. Specifically, combining electrochemical techniques together with cantilever devices is a highly efficient way to improve the performance of cantilever sensing. Several groups have made efforts towards the development of electrochemical-cantilever (ECC) based sensors (Chapman et. al., 2007; Lavrik et. al., 2004). However, one main limitation of cantilever based sensing is the unclear origins of surface stress (Godin et. al., 2010), which lead to poor reproducibility and unreliable results.  In order to further the understanding of surface stress and behaviour of the electrochemical cantilever system, we investigate the surface stress response induced by electrochemical processes happening on the cantilever surface. In this work we fabricated the silicon nitride cantilever chips with integrated nanoporous gold working, reference and counter electrodes, as shown in figure 1 and created an electrochemical-cantilever platform combined with microfluidic cell (Fischer et. al. 2011). Solutions containing 5 mM, 1mM, 500μM of [Fe (CN)6]3-/4- couple (with 200 mM, 40 mM, 20 mM KNO3 supporting electrolyte, respectively)  were measured on this platform by amperometry at a potential of + 0.45 V vs nanoporous gold applied. Direct and complementary information related to nanomechanical changes on the surface were obtained by optically measuring cantilever deflection. 2 RESULTS AND DISCUSSION As shown in figure 2, the results reveal that the concentration of [Fe(CN)6]3-/4- couple had an effect on the surface stress generated on the cantilever, i.e. a higher concentration resulted in a larger change in surface stress, in accordance with amperometric results that the larger limiting current. The main contribution to this change in surface stress is the charge accumulated on the surface of the cantilever after the current reaches a limiting value during the period of the applied potential. The complex physical/chemical event occurs on the cantilever in very short period (less than 2 secs) from applying a certain potential to reaching the limiting current, but the mechanical signal data collection is relatively slow (e.g. one data point per second). Therefore, the electrochemical and mechanical behaviour of cantilever during this period is difficult to interpret. The change of surface stress in a solution of 500 μM [Fe(CN)6]3-/4- with 20 mM KNO3 does not follow the trend of the 5 mM and 1 mM [Fe(CN)6]3-/4- solutions, , indicating the concentration of electrolytes also might strongly impact the electromechanical behaviour, in particular, when it is below a critical value. Hence, dependency of electrolyte concentration on the surface stress was studied by the amperometric method (data are not shown here). We observe that the lowest concentration electrolyte has the strongest influence on the surface stress change of cantilever, in which case influence of uncompensated resistance, as well as migration effect should be taken into consideration. These results suggest that an optimal combination of mechanical and amperometric  196-2 methods is a powerful strategy to acquire more details during electrochemical processes, demonstrating the electrochemical cantilever platform as a competitive chemical sensing tool.   (a)  (b) Figure 2 (a) Surface stress (top signal) and applied potential (bottom signal) are plotted versus time for a cantilever in the [Fe (CN)6]3-/4- couple solution with various concentrations. (b) Amperometric current–time responses in the [Fe (CN)6]3-/4- couple in KNO3 electrolytes with various concentrations and milliQ water. 3 ACKNOWLEDGEMENTS This research was funded under a Villum Kann Rasmussen centre of Excellence (NAMEC). REFERENCES Chapman P. J., Long Z., Datskos P., Archibald G., R. and Sepaniak M. J. (2007). Differentially ligand-functionalized microcantilever arrays for metal ion identification and sensing. Analytical Chemistry, vol. 79, no. 18, pp. 7062–7068, 2007. Fischer L.M., Dohn S., Boisen A., Tenje M. (2011). An electrochemical-cantilever platform for hybrid sensing applications. In Proceedings of the IEEE: The 24th International Conference on Micro Electro Mechanical Systems (IEEE MEMS 2011), Canc´un, Mexico, 24-27 January 2011, Paper No. 0338. Godin M., Tabard-Cossa V., Miyahara Y., Monga T., Williams P. J., Beaulieu L. Y., Lennox R. B. and Grutter P. (2010). Cantilever-based sensing: the origin of surface stress and optimization strategies. Nanotechnology, vol. 21, no. 7, 075501.  Figure 1 An image of the ECC chip, with the cantilever working electrodes (WE) in the channel, as well as the counter (CE) and reference (RE) electrodes.  196-3 Lavrik N. V., Sepaniak M. J., and Datskos P. G. (2004). Cantilever transducers as a platform for chemical and biological sensors. Review of Scientific Instruments, vol. 75, no. 7, 2229–2253. 

Investigation of Electrochemical and Mechanical Behaviour of Electrochemical Cantilever Sensor by Electrochemical methods

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Investigation of Electrochemical and Mechanical Behaviour of Electrochemical Cantilever Sensor by Electrochemical methods

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