Ionic conductive hydrogels formed through hydrophobic association for flexible strain sensing

Over the years, hydrogels have been extensively studied and got a lot of attraction as wearable sensors, due to their stretchability and flexibility, however, their application of repetitive sensing is greatly constrained owing to their lengthy response time and poor mechanical properties. In the current study, a stretchable and conductive hydrogels were fabricated by interlinking lauryl methacrylate with acrylamide and sodium alginate via a physical crosslinked network, resulting in enhanced mechanical properties due to micelle dynamic crosslinking points and hydrogen bonding. The observed tensile strain was 1400 % with a fracture stress of 390 kPa and low hysteresis energy. In addition, the hydrogel strain sensor exhibited a wide range of strain (25–300 %), excellent cyclic stability of more than 350 cycles and showed quick response time of 200 ms. Moreover, the hydrogel is also designed to be a built-in sensor to monitor slight and subtle changes in the human body such as wrist, finger flexion, and swallowing. The strain sensors are also capable of recognizing letters written over it sensitively and distinctively. Hence, we believe that these hydrogel-based strain sensors could be applied in future wearable electronic devices and for human movement monitoring.