What question did this study set out to answer?

To develop flexible, solid-state ionic pressure sensors with enhanced performance characteristics.

April 12, 2026Open Access

Flexible Crosslinked Poly(ionic liquid)s for All-Solid-State High-Performance Self-Powered Ionic Pressure Sensors

VSVladislav Y. Shevtsov JGJuan A. GuerreroUniversity of Mons SGSebastjan GlinšekLuxembourg Institute of Science and Technology

Key Points

To develop flexible, solid-state ionic pressure sensors with enhanced performance characteristics.
Designed and synthesized two ionic liquid-like monomers: cationic (M-BIM) and anionic (M-TFSI).
Co-polymerized monomers with poly(ethylene glycol) monomethacrylate and dimethacrylate.
Optimized film thickness, interfacial electrode layer geometry, and type to improve performance.
Tested various charge-carrier types to assess their effects on sensitivity and voltage output.
Achieved highly ion-conductive films with mechanical properties ranging from 0.4 to 1.0 MPa.
Demonstrated an ionic conductivity of up to 2.3 × 10^-6 S cm^-1 at 25 °C.
The optimized sensor showed a linear voltage response across a pressure range of 0-80 kPa.
Reported a rapid recovery time of 0.2 seconds and an output voltage of 190 mV over 1000 loading cycles.

Abstract

Despite the progress achieved in ionic-based sensors, the growing demand for soft and flexible devices has highlighted several key requirements for the next generation of materials: (1) complete elimination of liquid phases that may evaporate or leak; (2) sufficient mechanical robustness for stable operation over repeated loading cycles; (3) facile device assembly; (4) high voltage output and sensitivity; and (5) a broad operational pressure range. To address these challenges, two complementary ionic liquid-like monomers (ILMs) were designed and synthesized: a cationic (M-BIM) and an anionic (M-TFSI) monomer, each incorporating a butylimidazolium (BIM+) or bis(trifluoromethylsulfonyl)imide (TFSI-) fragment covalently bonded to a methacrylate group together with their complementary counterions (respectively, TFSI- or BMIM+). Their copolymerization with poly(ethylene glycol) monomethacrylate (PEGM) and dimethacrylate (PEGDM) and optimization of the composition afforded flexible, self-standing, highly ion-conductive films combining good mechanical properties (E' = 0.4-1.0 MPa) with high ionic conductivities (up to 2.3 × 10-6 S cm-1 at 25 °C). Systematic optimization of film thickness, interfacial electrode layer (IEL) geometry, and IEL metal type revealed that sputtered gold IELs effectively suppressed signal drift and shortened response times, while platinum IELs markedly enhanced voltage generation. Comparison among sensors with mobile anions, mobile cations, and mixed carriers demonstrated that the charge-carrier type critically governs both sensitivity and voltage amplitude. The optimized sensor, based on the anionic M-TFSI formulation, featuring a 0.35 mm-thick film and rectangular Pt IEL exhibited a linear potential-pressure dependence across the entire range (0-80 kPa), an ultrafast recovery time of 0.2 s, and an exceptional output voltage of 190 mV, maintaining stable operation over 1000 loading cycles.

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