Highly stretchable strain sensors with reduced graphene oxide sensing liquids for wearable electronics

Abstract

Strain sensors with high sensitivity, broad sensing ranges and excellent durable stability are highly desirable due to their promising potential in electronic skins and human-friendly wearable interactive systems. Herein, we report a high-performance strain sensor based on rGO (reduced graphene oxide)/DI (deionized water) sensing elements. The strain sensors were fabricated by using Ecoflex rubber filled with rGO/DI conductive liquids via template methods, making the process simple, low-cost and scalable. The as-assembled strain sensors can be used to reflect both stretching and compressing with high sensitivity (a maximum gauge factor of 31.6 and a pressure sensitivity of 0.122 kPa), an ultralow limit of detection (0.1% strain), and excellent reliability and stability (>15 000 cycles for pressuring and >10 000 cycles for stretching). In particular, the maximum sensing range is up to 400%, much wider than that of the sensor recently reported. More significantly, the strain sensors are able to distinguish between touch/compressive (resistance decrease) and tensile (resistance increase) deformation, which has not been explored before. This interesting property of strain sensors is due to the micro-contact of nanomaterials in a liquid environment. The sensing liquid of the device can be refilled when it fails, and this enables the recycling of the materials and reduces the waste rate. Therefore, it is attractive and promising for practical applications in multifunctional wearable electronics such as the detection of acoustic vibration, human vocalization and other human motions.

Wearable multifunctional printed graphene sensors

“…In this paper, we exploit the piezoresistance of graphene electrodes printed on flexible polyimide (PI) films. Graphene has been extensively exploited recently as an alternative to traditional materials, due to its superior properties, such as high conductivity, flexibility, transparency, and biocompatibility, 17,18 There is a number of reports investigating electromechanical properties of the graphene based on CVD, [19][20][21] mechanically exfoliated graphene, 22,23 graphene oxide, [24][25][26] and hydrogenated graphene oxide. 20,27 The intrinsic piezoresistivity of single-layer graphene is rather limited as the hexagonal mesh of graphene can withstand strains only below~0.7% with gauge factors (GF) of~1.4-2.…”

“…20,27 The intrinsic piezoresistivity of single-layer graphene is rather limited as the hexagonal mesh of graphene can withstand strains only below~0.7% with gauge factors (GF) of~1.4-2. [28][29][30][31] Meanwhile, the responsivity of multilayered structures, such as graphene oxide [24][25][26] and hydrogenated graphene oxide is significantly higher. 20,27 The high variation of the electrical resistance of multilayer samples under strain was explained by the displacement of the layers and changing their overlapping area, which provides the ability to use these structures for force and strain sensors.…”

Strain Improving the Performance of a Flexible Monolayer MoS2 Photodetector

“…[8,9] The piezoresistive effect is that the band gap structure of the semiconductor can be changed by strain, which can modulate the transport behavior of materials. [12] The piezoresistive materials have been widely used for improving the transport properties of transistor and force sensor. [12] The piezoresistive materials have been widely used for improving the transport properties of transistor and force sensor.…”

Highly Stretchable, Transparent, and Bio‐Friendly Strain Sensor Based on Self‐Recovery Ionic‐Covalent Hydrogels for Human Motion Monitoring

“…At present, the representative strain sensors have been well developed by embedding conductive fillers (e.g., carbon nanotubes (CNTs), [18,19] graphene, [20][21][22] Ag nanowires, [23,24] and metallic nanoparticles [25,26] ) into elastomeric substrates. [27,28] However, most of these devices have low stretchability (usually <200% strain) and poor recoverability, also stiff characteristic against seamless combination with body regions, leading to great difficulties for body adhesion. [29,30] It is well known that hydrogel is a bioorigin flexible material, which consists of a great deal of water and 3D chemically or physically linked polymer networks.…”