Nanoscale control of morphologies enables robust and elastic ionogel for sensitive and high-resolution pressure sensing over wide linear range

Abstract

Ionogel, an excellent biomimetic sensing material due to high stability and wide operating temperature range, holds substantial promise for wearable devices, while still possesses big challenges in integration of desirable mechanical properties and sensing performance via straightforward strategies. Here, a tailored ionogel with tissue-matched softness (Young’s modulus <10.7 ± 0.8 kPa), appropriate adhesion, remarkable compression resistance (>1 MPa), resilience and sensing reliability by copolymerizing two homologous monomers of acrylamide and N,N-dimethylacrylamide in 1-ethyl-3-methylimidazolium trifluoromethanesulfonate is developed by phase separation. Through fine adjustment of components, nanoscale transformation of microstructures from nanoporous structure to island structure, followed by bicontinuous structures results in distinct impact on optical, thermal, mechanical, and conductive properties of ionogels, and the intricate effects of phase-separated degree on nanoscale structural features and macroscopic performance have been revealed. The resultant ionogels are readily manufactured to versatile sensors for precise detection of body signals from subtle pulse to large body weights, achieving low detection limit (8 Pa), high pressure resolution (0.055 %) and good sensitivity (1.2 kPa⁻¹) over a broad linear range (0.008–1000 kPa), together with rapid response speed of tens of milliseconds and recovery speed of ∼20 s under extreme compression. This work delves into essential correlation between nanostructures of ionogel and its properties, and we expect the approach of tailoring functions of soft matter by hierarchical structures to provide guidance for future fabrication of flexible sensors in target applications.