Highly Stretchable, Tough, and Conductive Ag@Cu Nanocomposite Hydrogels for Flexible Wearable Sensors and Bionic Electronic Skins

Abstract

Flexible conductive materials and flexible electronic devices are driving the development of the next generation of cutting‐edge wearable electronics. However, the existing hydrogel‐based flexible conductive materials have limited tensile capacity, low toughness, and poor anti‐fatigue performance, resulting in narrow sensing area and insufficient durability. In this paper, a conductive nanocomposite hydrogel with high ductility, toughness, and fatigue resistance is prepared by combining silver coated copper (Ag@Cu) nanoparticles with gelatin followed by one‐step immersion in sodium sulfate (Na2SO4) solution. The salting‐out of gelatin in Na2SO4 solution greatly improve the mechanical properties of this gelatin‐based hydrogel. The uniform distribution of Ag@Cu nanoparticles inside the whole hydrogel endow the composite hydrogel with excellent electrical conductivity (1.35 S m−1). In addition, it displayed high and stable tensile strain sensitivity over a wide strain range (gauge factor = 2.08). Therefore, the Ag@Cu‐Gel hydrogel is sensitive and stable enough to be successfully utilized as flexible wearable sensor for detecting human motion signals in real time, such as bending of human joints, swallowing, and throat vocalization. Furthermore, this hydrogel is also suitable for application as electronic skin for bionic robots. The above results demonstrate the promising application of Ag@Cu‐Gel hydrogel for wearable electronics.

β-Cyclodextrin-Based Ultrahigh Stretchable, Flexible, Electro- and Pressure-Responsive, Adhesive, Transparent Hydrogel as Motion Sensor

“…Highly stretchable as well as flexible sensing devices have drawn the incredible attention of scientific communities in the past few years owing to their various advantages and prospective applications in different arenas like soft robotics, strain sensors, electronic skin, stretchable displays, health issues monitoring, and so on . However, most of the elastomers are generally made up of semiconductors and metals, which get separated from each other under high strain.…”

“…Thus, the sensors are ruptured and their stability, conductivity, and sensing action decreases . Consequently, to overcome these problems, various soft polymers and hydrogels are introduced as a substitute to new artificial skin. ,, The flexible nature and high water retention capability of the hydrogels are thus extensively used to fabricate various sensing devices. The large amount of water molecules present in the hydrogel network provide an easy transportation path for electrons and conductive ions. , Their mechanical features also have a resemblance to those of human skin.…”

A Multifunctional Skin‐Like Sensor Based on Liquid Metal Activated Gelatin Organohydrogel

“…Hydrogel is actually a 3D polymer network containing large amount of water. Owing to its similar structure to bio-tissues, [1][2][3][4] hydrogel-based wearable electronics are superior to the traditional elastomer counterparts, not only because their mechanical property is close to human skin (Young's modulus = 25-1000 kPa), [5][6][7][8] but also because the wearing on-skin, [35] or implantable electronics [36,37] and will not cause further environmental issues. In recent few years, biopolymer/LM hydrogels have attracted more and more research interests.…”

“…Hydrogel is actually a 3D polymer network containing large amount of water. Owing to its similar structure to bio‐tissues, [ 1–4 ] hydrogel‐based wearable electronics are superior to the traditional elastomer counterparts, not only because their mechanical property is close to human skin (Young's modulus = 25–1000 kPa), [ 5–8 ] but also because the wearing experience is dramatically improved. Despite the advantages, there are still existing challenges hindering the hydrogel‐based soft electronics toward practical use.…”

Multi‐Network Poly(β‐cyclodextrin)/PVA/Gelatin/Carbon Nanotubes Composite Hydrogels Constructed by Multiple Dynamic Crosslinking as Flexible Electronic Devices

“…into flexible hydrogels, have aroused significant attention in the field of smart, wearable and flexible electronic sensors. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] As flexible sensors, conductive hydrogels can quickly detect and respond to mechanical deformation or stress, and further convert the external stimuli into electrical output signals. [22,23] However, the traditional conductive hydrogels often lack self-healing property, which is unconducive to their practical applications.…”