Multi-environmentally stable and underwater adhesive DNA ionogels enabling flexible strain sensor

Abstract

The multifunctional conductive hydrogels with good flexibility and modifiability have been sufficiently investigated with their rapid development in flexible strain sensors. However, hydrogels inevitably loss water at higher temperature and freeze at subzero temperature, leading to the deterioration of mechanical performances and conductivities, which greatly restricts their application in flexible strain sensor. Besides, it is still challenging to fabricate robust adhesion hydrogels in both water and oil environments. Herein, inspired by the nucleobase-tackified strategy, high-performance ionogels were constructed through introducing the specific nucleobase pairs, guanine (G) and cytosine (C), into the polyacrylic acid (PAA) network in ionic liquids. The synergistic effect of hydrogen bonds, coordination bonds and ion-dipole interactions provided the excellent properties for ionogels, including strong mechanical properties (fracture strength of 54.38 kPa and toughness of 216.5 kJ m−3), high stretchability (∼738%), desirable ionic conductivity (155.6 mS m−1), good antifreezing, superior non-swelling behavior as well as tight adhesiveness in aqueous, oil and salt solutions. The ionogels were assembled to strain sensor by virtue of their exceptional characteristics, which exhibited brilliant stretching sensitivity (gauge factor of 4.24), wide strain window (0–600%), fast response time (183 ms), and excellent cycle stability. Especially, the ionogel sensor was capable of sensitive and stable detecting human activities signals in subzero temperature (−20 °C) and aquatic environment. Importantly, the ionogel sensor shows tremendous application foreground in harsh environment (coldness, hotness, and underwater) due to its remarkable mechanical stability and adhesive behavior in extreme condition and provides an effective strategy to develop high-performance wearable sensors.