Multiple-Language-Responsive Conductive Hydrogel Composites for Flexible Strain and Epidermis Sensors

Abstract

Conductive hydrogels are considered highly promising materials for developing skin-like sensors due to their excellent biocompatibility and mechanical flexibility. However, their limited stretchability, low toughness, and low fatigue resistance hinder their sensing capabilities and durability. To overcome these limitations, we developed a conductive hydrogel composite with high mechanical performance and the ability to respond to and identify different languages. The hydrogels are prepared by incorporating functionalized multiwalled carbon tubes (F-CNTs) into hydrophobically associated polyacrylamide (AM) and lauryl methacrylate (Lmc) hydrogels. To ensure the uniform dispersion of F-CNTs in the hydrogel network, the cationic surfactant cetyldimethylethylammonium bromide (CDAB) is used; the carboxylic group on F-CNTs cross-links the micelles and polymer chains through electrostatic interactions. The surfactant also facilitates the formation of hydrophobic interactions between the hydrogel matrix and the F-CNT surface. This greatly improves the mechanical properties of the hydrogel, resulting in excellent stretchability of 2016%, a toughness of 551.56 kJ m −3 , and an antifatigue property. The hydrogel also exhibits high tensile strain sensitivity with a gauge factor of 4.69 at 600% strain. The hybrid hydrogel-based sensors demonstrate excellent sensing capabilities, not only detecting full-range human activities but also differentiating different languages (English, Urdu, and Pushto) in both speaking and writing. Besides strain sensing, the hybrid hydrogel has the capability to mimic human skin for a touchable screen like a metal. These results highlight the potential of the F-CNT-based hybrid hydrogel as a wearable strain sensor for flexible devices.

Flexible Ionic Conductive Hydrogels with Wrinkled Texture for Flexible Strain Transducer with Language Identifying Diversity

“…Hydrophobic associations and electrostatic interactions were utilized to maintain the integrity of the LM, Amm, and DMAEAMC hydrogels. Pluronic 123 (P123) served as the micelle agent, with LM hydrophobic monomer diffusing into the micelles. , After polymerization with Amm and DMAEAMC, these micelles acted as cross-linking points for the hydrogel network. The wrinkled texture was generated by the hydrophobic photoinitiator, where micelles reduced the interfacial (surface) energy, resulting in wrinkled micro- or macro surfaces.…”

Bimetallic-MOF Tunable Conductive Hydrogels to Unleash High Stretchability and Sensitivity for Highly Responsive Flexible Sensors and Artificial Skin Applications

“…Nevertheless, the practical use of hydrogel-based wearable sensors has been hindered by their weak mechanical properties such as low stretchability, toughness, and insufficient resistance to fatigue. , These shortcomings translate into a limited sensing range and reduced durability. Recent efforts have focused on designing highly stretchable and robust hydrogels by leveraging reversible noncovalent interactions, such as ionic bonding, , hydrogen bonding, electrostatic interaction, and hydrophobic interactions, , in conjunction with well-designed network structures like macromolecular microparticles . Various types of hydrogels have been discovered to address these issues, including double-network hydrogels, hydrophobic association hydrogels, , ionically cross-linked hydrogels, , and composite hydrogels. , Among these, composite hydrogels stand out due to their exceptional elongation properties, and the incorporation of conductive nanoparticles further enhances their conductivity.…”

Controllable Shape Morphing Nanocomposite Hydrogels for Robust Multi-Stimuli-Responsive Actuators

“…Designing and developing smart hydrogels for soft actuators with controllable stimuli-responsive shape deformations have aroused tremendous research interests in recent years. − Taking advantage of delicate design of internal structure and precise control of external stimuli, , smart hydrogels can easily and programmatically change the shapes through controllable uneven swelling/deswelling. Following this principle, smart hydrogels with complex deformations such as bending, − folding, − and bucking and twisting − have been successfully explored as soft actuators for a wide range of applications. − Particularly, magnetism or near-infrared light stimuli-response contributes to the rapid and noncontact control ,,,, and superior mechanical properties serve to build the reusability and durability, , which enable the shape-deformable hydrogels to play a more important role in serving as actuators for extended promising applications.…”