Flexible mussel‐inspired hydrogel for transparent wearable strain sensors: Investigation of mechanical, physical properties, self‐healing, and electrical conductivity

Abstract

AbstractNowadays, flexible hydrogels with electrical conductivity have become extremely helpful with broad application scenarios in electronic membranes in human–machine boundaries. However, a design approach to adjust and ameliorate conductivity, mechanical strength, transparency, self‐healing, and good adhesion remains a challenge. One of these strategies is mussels‐mimicking adhesive hydrogels, presenting strong adhesion. Here, we aim to meet the challenge by pursuing a mussel‐inspired design approach, which leads to the formation of a transparent, self‐healing, adhesive, and electrically conductive hydrogel from dopamine (DA), pyrrole (Py), acrylamide (AM), functionalized iron, and copper ions as an advanced electronic sensor. The transparent hydrogels were prepared using a sonication polymerization method. The results have shown that hydrogels containing copper or iron have conductivity (12 × 10−4 or 27 × 10−4 S/cm), mechanical strength (11.2 or 18.4 kPa), elongation at break (EB: 652.231% or 660.198%) and gauge factors (GF: 3.04679, 2.93513). Also, hydrogels can maintain their conductivity if they are twisted or stretched. Self‐healing behavior, swelling, and water‐induced shape memory effect (SME) due to hydrogen bonds and π–π interactions were observed. The behavior of this hydrogel as wearable sensors in integration with different body tissues such as finger, wrist, breathing, and frown was investigated. The obtained hydrogels showed high sensitivity in different areas of the body, fast response time in the strain range of 0%–%500, and high adhesion and transparency.