Ionogels for flexible conductive substrates and their application in biosensing

Ionogels are highly conductive gels made from ionic liquids dispersed in a matrix made of organic or inorganic materials. Ionogels are known for high ionic conductivity, flexibility, high thermal and electrochemical stability. These characteristics make them suitable for sensing and biosensing applications. This review discusses about the two main constituents, ionic liquids and matrix, used to make ionogels and effect of these materials on the characteristics of ionogels. Here, the material properties like mechanical, electrochemical and stability are discussed for both polymer matrix and ionic liquid. We have briefly described about the fabrication methods like 3D printing, sol-gel, blade coating, spin coating, aerosol jet printing etc., used to make films or coating of these ionogels. The advantages and disadvantages of each method are also briefly summarized. Finally, the last section provides a few examples of application of flexible ionogels in areas like wearables, human-machine interface, electronic skin and detection of biological molecules.

Polyvinylpyrrolidone with ammonium iodide and 1-hexyl-3-methylimidazolium iodide ionic liquid-doped solid polymer electrolyte for efficient dye sensitized solar cell

Polymer electrolytes were prepared by doping polyvinylpyrrolidone and ammonium iodide ion with an ionic liquid (IL) 1-hexyl-3-methylimidazolium iodide. Polymer electrolytes were prepared by solution cast technique. Ionic conductivity was improved by the addition of IL which is studied using complex impedance spectroscopy by evaluating ionic conductivity. Using maximum electrical conductivity film, laboratory-scale dye-sensitized solar cell has been fabricated which shows stable performance.

Ionic liquid (1-hexyl-3-methylimidazolium iodide)-incorporated biopolymer electrolyte for efficient supercapacitor

The sole aim of the present article was to develop a highly efficient electrochemical double-layer capacitor (EDLC) using a solid polymer electrolyte. Solution cast technique was adopted to fabricate an efficient EDLC. Solid biopolymer electrolytes were synthesized based on corn starch as a host polymer and sodium chloride as well as ionic liquid (1-hexyl-3-methylimidazolium iodide) as dopants. The ionic conductivity of present system has been carried out using impedance spectroscopy. Detailed electrical, structural and thermal studies of polymer electrolytes have been carried out. An efficient EDLC has been fabricated using carbon-based electrodes and maximum conducting biopolymer electrolyte which shows promising result.

Determination of charge carrier transport properties of gellan gum–lithium triflate solid polymer electrolyte from vibrational spectroscopy

Mobility and number density of charge carriers are important parameters that influence the electrolyte conductivity. Therefore, knowing these parameters quantitatively is of great significance. In this work, solid polymer electrolytes have been prepared by solution casting technique using gellan gum complexes with lithium triflate (LiTf). The conductivity of the electrolyte increases from 3.35 × 10−8 S cm−1 (electrolyte with 10 wt% LiTf) to 5.38 × 10−4 S cm−1 (electrolyte with 40 wt% LiTf). The increase in conductivity was attributed to the increase in mobility and number density of charge carriers in the electrolyte from 6.63 × 10−9 cm2 V−1 s−1 to 1.25 × 10−6 cm2 V−1 s−1 and from 4.00 × 1020 cm−3 to 2.68 × 1021 cm−3, respectively. The electrolyte conductivity is seen to decrease as LiTf salts were added more than 40 wt% concentration due to the decrease of charge carrier mobility to 8.58 × 10−7 cm2 V−1 s−1. The variation of conductivity obtained in this work is dominantly influenced by the mobility of charge carriers in the electrolyte as proven from the Fourier transform infrared approach.