ISFET‐based ion sensors with photopolymerizable membranes

Abstract

This minireview summarizes the information on the development and application of ion-sensitive field-effect transistors (ISFETs) with UV-cured polyurethane ion-selective membranes. Among the advantages of photopolymerizable polymer membranes in comparison with traditional poly(vinyl chloride) are excellent adhesion to a solid sensor surface and very fast curing time. Moreover, processes of membrane deposition and curing are compatible with ISFETs fabrication technology which is important for sensors mass production. The paper presents specific features of photopolymerizable membranes and discusses required precautions in their preparation and treatment. Examples of various analytical applications of this kind of sensors are provided. Finally, the outlook and perspectives of further development in the field of miniature solid-state ion sensors are given.

G‐Quadruplex‐Filtered Selective Ion‐to‐Ion Current Amplification for Non‐Invasive Ion Monitoring in Real Time

“…By mimicking the in‐line K + recognition of the KcsA potassium channel, our hexyl‐modified monolithic G‐quadruplex produced a K + ‐selective ion flux across the freestanding ion‐impermeable lipid bilayer without water leakage; despite the same valency, Li + and Cl − were less favored than K + , exhibiting P Li / P K = 0.214 and P Cl / P K = 0.004, respectively. Compared to conventional valinomycin‐embedded polymeric membranes (30–100 µm in thickness), [ 32 ] our K + ‐selective membrane, which can be integrated into the OJID, is ultrathin (≈4 nm), highly K + ‐selective, and even non‐cytotoxic. Moreover, the neuron‐like ion‐to‐ion signal transduction of the OJID (10 mm × 10 mm × 1 mm) allowed the direct conversion of K + effluxes into amplified ionic currents (up to 20× amplification ratio), differentiating our ionic device from conventional potentiometric ion recorders that require mediation of electrical potential changes.…”

Modeling Non-Equilibrium Ion-Transport in Ion-Selective-Membrane/Electrolyte Interfaces for Electrochemical Potentiometric Sensors

“…Figure 4 reports the comparison of the membrane potential recorded in the experiments in [39] and the simulation results sampled at the Interface 1 (see Fig. 3.a), versus [ClO − 4 ] in 1 The NE equation in Fig. 3.b is…”

“…Here, a stable interface with gate oxide is needed [1] to make sure that the potential changes at the ISM/electrolyte interface (function of the ionic concentrations) modify the gate voltage of the FET, V g′ , that is:…”

“…I ON-selective-membranes (ISM) are essential elements in ion-discriminating devices. Their applicability ranges from electrochemical potentiometric sensors to ion-actuators for drug-release and to iontronic components capable of performing logic operations [1]- [4]. In the case of ion-sensing, ISMs are also responsible of the transduction mechanism itself converting a concentration gradient into a potential difference [5], that is a measurable physical quantity.…”

“…1.b) preventing physical transfer of ions, so that ion-transfer processes can only occur between the ISM and the sample solution. Here, the membrane potential can be recorded directly at the solid interface, e.g., through ion-to-electronic conversion, such as in solid-contact ionselective electrodes (SC-ISEs) [2], [6], or used for field-effect modulation of an electric current, as in ion-sensitive FETs (ISFETs) [1], [7], [8]. Note that in ISFETs employing ISMs, the sensing mechanism is ruled by ion-transfer across the membrane and the electrolyte rather than surface reactions at the solid/electrolyte interface (e.g., site-binding model for oxide/electrolyte interface at the base of pH sensing [9]).…”