Polymeric Complex-Based Transparent and Healable Ionogels with High Mechanical Strength and Ionic Conductivity as Reliable Strain Sensors

Abstract

Transparent and healable ionogels with very high mechanical strength, ionic conductivity, and resilience were fabricated for use as strain sensors with satisfactory reliability. The ionogels were fabricated by casting an aqueous solution of poly­(vinyl alcohol) (PVA)–poly­(vinylpyrrolidone) (PVP) complexes and 1-ethyl-3-methylimidazolium dicyanamide ([EMIm]­[DCA]), followed by evaporation of water at room temperature. The use of [EMIm]­[DCA] endowed the resulting ionogels with ionic conductivity at room temperature as high as 19.7 mS cm–1. Owing to the synergy between the abundant number of hydrogen bonds between PVA and PVP and the crystallized PVA segments that served as nanofillers, the resulting ionogels had good mechanical properties with a tensile stress of 7.7 MPa, a strain of 821%, and good resilience. In addition, the resulting ionogels showed rapid and repeatable sensing signals over a wide strain range (0.1–400%). This enabled them to detect both vigorous muscle movements, such as walking and jumping, and subtle muscle movements, such as pulse. Moreover, owing to the reversibility of hydrogen bonds, physically damaged mechanical properties, conductivity, and sensing ability of the ionogels could be conveniently healed with the assistance of water.

Recent Progress in Essential Functions of Soft Electronic Skin

“…Similar to the hydrogels, some ionogels can be finely healed because of some reversible interactions, thus endowing the resultant sensor with self-healing capability. [105,116,259] Weng et al [116] fabricated the highly stretchable and self-healing ionogel based on the mixture of PVA complexes and ILs. As the red and blue ionogels were contacted with a drop of water dripping on the fractured surfaces, these two halves of the ionogels were reconnected after healing under ambient conditions (40% RH, 25 °C) for 1 h (Figure 16a).…”

“…For instance, Xu et al [264] proposed self-similar serpentine geometries to interconnect the segmented stiff islands containing the active materials Reproduced with permission. [116] Copyright 2020, American Chemical Society. e) Images of self-healing process of PU/ILs ionogel.…”

“…d) Variation in relative resistances of pristine and healed PVA/PVP/ILs ionogelbased sensor over 500 loading−unloading cycles at a strain of 50%. The inset is the enlarged image of the last ten cycles during the measurement.Reproduced with permission [116]. Copyright 2020, American Chemical Society.…”

Ionogel-based flexible stress and strain sensors

“…As seen from the table, solution cast is the easiest forming process to synthesis ionogel material (Figure 3(a)). Hence, most of IFSS are thin film structure originated from the solution-casted synthesis process of ionogel [40,41,44,[46][47][48]54,56,57,60,61]. As a stretchable strain sensor, simple film is the optimum device structure.…”

Self-Healing Hydrophilic Porous Photothermal Membranes for Durable and Highly Efficient Solar-Driven Interfacial Water Evaporation

“…With the progress in supramolecular chemistry and synthetic chemistry, various self-healing polymers that are capable of healing damage by themselves to restore the mechanical and/or chemical properties have been Page 2 of 31 CCS Chemistry 3 successfully synthesized. [20][21][22][23] In addition, by combining self-healing polymers with functional materials, plenty of self-healing functional materials with superhydrophobicity, [24][25][26][27] antifouling, [28][29][30] electrical conductivity, [31][32][33][34] sensing, [35][36][37][38][39][40][41] and other functions [42][43][44][45][46][47][48][49][50] have been fabricated, significantly decreasing maintenance costs and promoting safety, reliability, and service life. The design and fabrication of self-healing materials with photothermal and water transportation capabilities that can repair their functions upon damage would be a judicious solution to increase the stability and service life of solar-driven interfacial evaporators.…”