We report the design of a silicon chip dedicated to the in-situ monitoring of soil nitrogen cycle in wheat crop. Our study shows that ion-sensitive field effect transistor (ISFET) microsensors are suitable for quick on-site or long-term analysis of nutrients measured directly in soil as opposed to soil extracts analysis. Our pH-ISFET recorded soil pH for six months with results in good accordance with standard sampling method and without any loss of sensitivity. The adaptation of pH-ISFET in pNO₃ and pNH₄-ISFET allowed, for the first time, the in-situ measurements of natural variations of soil nitrogen contents caused by microorganisms’ activity

We present a sensor platform associated to silicon-nanowire chemical field effect transistors (Si-nw-ChemFET). Innovations concern the use of networks of suspended silicon N⁺/P/N⁺ nanowires as conducting channel, the realization by thermal oxidation and Atomic-Layer Deposition (ALD) of a SiO₂/Al₂O₃ gate insulator all-around the silicon nanowires, and their final integration into covered SU8-based microfluidic channels. The Si-nw-MOSFET/ChemFET fabrication process and electrical/electrochemical characterizations are presented. The fabrication process did not need an expensive and time-consuming e-beam lithography, but only fast and “low cost” standard photolithography protocols. Such microdevice will provide new opportunities for bio-chemical analysis at the micro/nanoscale.

This work presents the modelling of impulsional pH variations in microvolume related to water-based electrolysis and hydrogen peroxide electrochemical oxidation using an Electrochemical Field Effect Transistor (ElecFET) microdevice. This ElecFET device consists of a pH-Chemical FET (pH-ChemFET) with an integrated microelectrode around the dielectric gate area in order to trigger electrochemical reactions. Combining oxidation/reduction reactions on the microelectrode, water self-ionization and diffusion properties of associated chemical species, the model shows that the sensor response depends on the main influential parameters such as: (i) polarization parameters on the microelectrode, i.e., voltage (V_p) and time (t_p); (ii) distance between the gate sensitive area and the microelectrode (d); and (iii) hydrogen peroxide concentration ([H₂O₂]). The model developed can predict the ElecFET response behaviour and creates new opportunities for H₂O₂-based enzymatic detection of biomolecules.

An all-integrated on-chip electrochemical microcell (10 × 11 mm²) is developed using silicon technology. The potentiometric nitrate ion detection is based on the functionalization of the working microelectrode array with a polymer membrane in fluoropolysiloxane (FPSX) containing ionophore tetradodecylammoniumnitrate (TDDAN) and ionic additive potassium tetrakis[3,5-bis(trifuoromethyl)phenyl]borate (KTFPB) to form an all-solid-state ion selective electrode (ISE). The addition of an ion-to-electron transducing layer between the platinum working electrode and the polymer membrane helped to improve the sensor performances, especially the response time, the sensitivity, and the stability. Composites formed with two conductive polymers were compared: Polyethylenedioxythiophène (PEDOT) and Polypyrrole (PPy), doped with Poly(styrene sulfonate) or double-walled carbon nanotubes (DWCNTs).

This work deals with the development of electrochemical transducers for the analysis of the metabolic status of mitochondria isolated from leukemic cells. It proposes the use of ring nanoelectrodes (RNE) integrated into microwell arrays for the simultaneous monitoring of the oxygen (O₂) consumption and the hydrogen peroxide (H₂O₂) production. The sensor enabled the real-time recording of the oxygen consumption of approximately 10,000 isolated mitochondria. Solutions are now proposed to detect H₂O₂ production and to reduce the number of mitochondria under test, targeting the single mitochondrion analysis.