An Ultrastretchable Gradient Ionogel Induced by a Self-Floating Strategy for Strain Sensing

Abstract

The fabrication of gradient ionogels for flexible strain sensors remains challenging because of the complex preparation procedures, and it is still difficult to prepare highly stretchable ionogels (strain > 10000%). In this study, a strategy is proposed to successfully fabricate gradient ionogels and apply them to flexible strain sensors by utilizing the self-floating character of the polysiloxane cross-linker. A gradient ionogel with ultrahigh stretchability (>14000%) is prepared via a one-step in situ photopolymerization process of the precursor with long-chain poly(dimethylsiloxane) bis(2-methyl acrylate) (PDMSMA). PDMSMA, which has a self-floating ability and excellent flexibility, induces a gradient composition distribution in the ionogel, thereby endowing the ionogel with superior stretchability and gradient changes in conductivity and adhesivity from the top to the bottom layer. Because of multiple molecular interactions, the bottom surface of the ionogel possesses good resilience and selfadhesion, whereas the top surface, which has a high PDMSMA content, shows a nonsticky performance. As a result, a singular gradient ionogel having both a sticky bottom surface and a nonsticky top surface is achieved. Furthermore, the flexible strain sensor that is created based on these gradient ionogels exhibits high sensitivity (its gauge factor reaching 5.08), a wide detection range (1− 1500%), fast response times, and good linearity. Notably, the detection signal remains repeatable over 1000 uninterrupted strain cycles. The fabricated strain sensor was further utilized to monitor joint movements and physiological signals. This work provides a facile strategy for fabricating gradient ionogels and shows their application potential in the field of flexible electronics.

High-sensitivity and ultralow-hysteresis fluorine-rich ionogel strain sensors for multi-environment contact and contactless sensing

“…51–53 Moreover, under high tensile strain, the conformation of the network structure is also altered with a more ordered arrangement of the polymer chains, which further weakens the mobility of the dissociative ions and leads to higher GF value. 54,55 The sensitivity of our ionogel sensors is superior to most recently reported ionogel strain sensors operating in air and even more competitive for underwater sensing applications 29,30,32,41,48,50,56–60 (Fig. 5e).…”

Rapid self-healing and superior toughness in ionically crosslinked polymer ionogels and strain sensing applications

“…These outstanding properties make zwitterionic nanocomposite gels promising for skin strain sensors to monitor body movement. 22–25…”

Hydrophobic TPU/CNTs-ILs Ionogel as a Reliable Multimode and Flexible Wearable Sensor for Motion Monitoring, Information Transfer, and Underwater Sensing

“…This sensor showed an ultrawide sensing range (up to 700%), ultralow detection limit (0.05%), fast response time (173 ms), and recovery time (120 ms). Li et al prepared gradient ionogels with ultrahigh stretchability (>14,000%) by one-step in situ photopolymerization of precursors with long-chain polydimethylsiloxane bis (methyl methacrylate) (PDMSMA) and applied them to flexible strain sensors. The strain sensor based on gradient ionization gel has high sensitivity (its measurement factor reaches 5.08), a wide detection range (1–1500%), fast response time, and good linearity.…”