[Chemosensors] Microfluidic Electronic Tongue Applied to Soil Analysis
Precision agriculture is crucial for increasing food output without expanding the cultivable area, which requires sensors to be deployed for controlling the level of nutrients in the soil. In this paper, we report on a microfluidic electronic tongue (e-tongue) based on impedance measurements which is capable of distinguishing soil samples enriched with plant macronutrients. The e-tongue setup consisted of an array of sensing units made with layer-by-layer films deposited onto gold interdigitated electrodes. Significantly, the sensing units could be reused with adequate reproducibility after a simple washing procedure, thus indicating that there is no cross-contamination in three independent sets of measurements. A high performance was achieved by treating the capacitance data with the multidimensional projection techniques Principal Component Analysis (PCA), Interactive Document Map (IDMAP), and Sammon’s Mapping. While an optimized performance was demonstrated with IDMAP and feature selection, during which data of a limited frequency range were used, the distinction of all soil samples was also possible with the well-established PCA analysis for measurements at a single frequency. The successful use of a simple microfluidic e-tongue for soil analysis paves the way for enhanced tools to support precision agriculture.
Maria L. Braunger 1, Flávio M. Shimizu 2, Mawin J. M. Jimenez 1, Lucas R. Amaral 3, Maria H. de Oliveira Piazzetta 4, Ângelo L. Gobbi 4, Paulo S. G. Magalhães 3, Varlei Rodrigues 1, Osvaldo N. Oliveira Jr. 2 and Antonio Riul Jr. 1,* 1 Department of Applied Physics, “Gleb Wataghin” Institute of Physics, University of Campinas—UNICAMP, 13083-859 Campinas, SP, Brazil 2 São Carlos Institute of Physics (IFSC), University of São Paulo (USP), P.O. Box 369, 13566-590 São Carlos, SP, Brazil 3 School of Agricultural Engineering, University of Campinas—UNICAMP, 13083-875 Campinas, SP, Brazil 4 Brazilian Nanotechnology National Laboratory (LNNano), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-970 Campinas, SP, Brazil * Correspondence: Tel.: +55-19-3521-5336 Academic Editor: Manel Del Valle Received: 24 February 2017 / Accepted: 25 April 2017 / Published: 27 April 2017