Water‐Saturated Ion Gel for Humidity‐Independent High Precision Epidermal Ionic Temperature Sensor

Abstract

Although ion gels are attractive sensing materials for deformable epidermal sensors or implantable devices, their sensing performances are highly affected by environmental humidity change, so that their sensing reliability cannot be secured. This study proposes a new concept of maintaining the high-precision temperature sensing performance of highly deformable ion gel sensors. In this approach, a hydrophobic ion gel sensing layer is kept water-saturated by attaching a hydrogel layer, rather than attempting to completely block water penetration. This study performs experimental and theoretical investigation on water concentration in the ion gel, using the analysis of mass transportation at the interface of the ion gel and the hydrogel. By using the charge relaxation time of the ionic molecules, the temperature sensor is not affected by environmental humidity in the extreme range of humidity (30%-100%). This study demonstrates a highly deformable on-skin temperature sensor which shows the same performance either in water or dry state and while exercising with large strains (𝝐 = 50%).

Cytoskeleton-inspired hydrogel ionotronics for tactile perception and electroluminescent display in complex mechanical environments

“…In some cases, e.g., when used for artificial skins and soft robotics, HIs are required to carry significant mechanical loads and/or undergo substantial deformation. 16,17 These loads and deformations can be either static or dynamic as well as continuous and instantaneous. [18][19][20] Due to these complex mechanical environments, the mechanical strength, toughness, and fatigue resistance of HIs need to be enhanced in order to ensure the reliability and stability of the device for long-term use.…”

Highly stretchable, self-adhesive, ambient-stable, and wide-temperature adaptable hydrophobic ionogels for wearable strain sensors

“…[8][9][10][11][12][13][14][15][16] However, with the increasing demands, the current ionogel-based flexible devices usually suffer from weak environmental adaptability and stability. [17][18][19] Therefore, highperformance ionogels with strong adaptability under extreme environments, a broader range of operability, and excellent durability are urgently desired for practical applications. 20 Commonly, ionogels are composed of an ionic liquid (IL) as the dispersing medium and a special structural network formed by some nanoparticles, small molecules, and polymers.…”

“…8–16 However, with the increasing demands, the current ionogel-based flexible devices usually suffer from weak environmental adaptability and stability. 17–19 Therefore, high-performance ionogels with strong adaptability under extreme environments, a broader range of operability, and excellent durability are urgently desired for practical applications. 20…”

Humanoid Ionotronic Skin for Smart Object Recognition and Sorting

“…21−24 Nevertheless, humanoid ISs are not only required to maintain their structural stability in practice use, but also need to bear significant mechanical loads and accommodate substantial deformation. 4,25 These loads and deformations can be either static or dynamic as well as continuous or instantaneous. 4,26−28 Under such complex mechanical environments, a balance between the mechanical strength and toughness of the ISs is required to ensure the reliability and stability of humanoid robots under long-term use.…”

“…Moreover, it needs to be able to perceive and interact with the external environments in real-time. − In these respects, ionotronic skins (ISs) have significant advantages compared to other artificial skin materials, such as polymer-based nanocomposites, − conductive polymers, − liquid metals, − and geometrically constrained metal mesostructures, − due to their similarities to biological tissues in terms of mechanical and electrical features. ISs have been proposed as a potential bridge between humans and robots to create bioelectronic interfaces. − Nevertheless, humanoid ISs are not only required to maintain their structural stability in practice use, but also need to bear significant mechanical loads and accommodate substantial deformation. , These loads and deformations can be either static or dynamic as well as continuous or instantaneous. ,− Under such complex mechanical environments, a balance between the mechanical strength and toughness of the ISs is required to ensure the reliability and stability of humanoid robots under long-term use. However, achieving such mechanical balance still remains a challenge for ISs.…”