Two‐Photon Nanolithography Enhances the Performance of an Ionic Liquid–Polymer Composite Sensor

Abstract

Continuous development of fabrication technologies, such as two‐photon polymerization (2PP), allows the exact reconstruction of specific volume shapes at micro‐ and nanometer precision. Advancements in the engineering of new materials, such as ionic liquids (ILs), are bringing superior advantages in terms of material characteristics, facilitating a combination of optical and electrical properties, as well as lithographic capabilities. In this paper, 2PP is utilized for structuring of a novel IL–polymer composite in a single‐step manufacturing process with high resolution, down to 200 nm, and high aspect ratio, up to 1:20. The composition, based on a photosensitive photoresist (e.g., IP‐L 780 or SU‐8) and the IL 1‐butyl‐3‐methylimidazolium dicyanamide, possesses a good ionic conductivity (in the range of 1–10 mS cm−1) over a wide frequency bandwidth (1 kHz–1 MHz), an electrochemical window of 2.7 V, and a good optical transparency (transmission value of 90% for a 170 μm thick film). The fabricated structures are characterized and the phenomenon of enhanced conductivity (up to 4 S cm−1) is explained. Two potential applications, including temperature and relative humidity sensing, are demonstrated as examples. The results suggest a new advanced approach for material structuring that can be regarded as highly most promising for a wide range of applications.