3D printable double-network ionogels with a multi-angle zigzag pattern for enhanced linearity and sensitivity of stretchable ionic sensors

With a considerable attention in wearable smart electronic devices, stretchable sensors are of great significance to meet the requirements of monitoring various human motions. However, simultaneously achieving both high sensitivity and a wide linear sensing range poses a significant challenge. In this study, we address this challenge by designing a strain sensor with a multi-angle zigzag pattern through 3D printing a double-network (DN) ionogel. A physically crosslinked poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) polymer network in the gel offers adequate viscosity for high quality 3D printing. The chemically crosslinked poly (ethylene glycol) diacrylate (PEGDA) polymer network in the DN ionogel provides sufficient mechanical integrity for the ionogel, ensuring reliable operation under reversible mechanical deformations. To enhance both the sensitivity and linear sensing range of the strain sensors, we employed a multi-angle zigzag pattern using 3D printing that can sequentially open with large (20 degrees), middle (14 degrees), and small (8 degrees) angles during stretching, and close in reverse order during contraction. Through this strategy, we achieved a record-high gauge factor of 114 and a linear response across over a broad sensing range of 100 %. These high performances are consistently maintained through repetitive mechanical deformations over a substantial period of 50,000 s, as well as under diverse temperature and humidity conditions. The resulting stretchable strain sensors can precisely detect various human motions and convert them into electrical signals.