Sheath–Core Fiber Strain Sensors Driven by in-Situ Crack and Elastic Effects in Graphite Nanoplate Composites

Abstract

Flexible and stretchable electronics, e.g., graphite-nanoplatelet-based (GNP-based) nanocomposite devices, have attracted great interest due to their potential application in health care, robotics, and mechatronics technology. However, the deficient sensors with manipulation of low sensitivity, sluggish responsivity, sophisticated fabrication process, and poor repeatability notoriously limit their industrial applications. For an enhancement in the spontaneous sensitivity, flexibility, and wearability in GNP-based strain sensors, in this report, synergistic crack and elastic effect engineering is employed and in turn significantly enhances the sensitivity with a gauge factor of 20 at a strain of 30% and the stability in our developed sheath–core fiber (SCF) strain sensors. Upon reliable device integration, it is demonstrated that the developed SCF strain sensor could detect the movement of a human joint effectively with generating a resistance change rate ΔR/R 0 up to 600%. Furthermore, a controlling device system based on the SCF strain sensor has been manufactured at the circuit level to realize the real-time control of a robot hand, such as copying gestures and playing piano.

Wearable and Stretchable Strain Sensors: Materials, Sensing Mechanisms, and Applications

“…A crucial step in the design of stretchable strain sensors is the selection of appropriate materials, assembled structures, and fabrication methods. Various conductive materials including carbon nanomaterials (e.g., carbon blacks [CBs], carbon nanotubes [CNTs], graphene and its derivatives), [6,9,34,[52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70] metal nanowires (NWs), nanofibers (NFs), and nanoparticles (NPs), [8,16,[71][72][73][74][75][76][77][78][79] MXenes (e.g., Ti 3 C 2 T x ), [10,80,81] ionic liquid, [82,83] hybrid micro-/nanostructures, [84][85][86][87][88][89][90][91][92][93]…”

“…Stretchable strain sensors based on NWs and flakes particularly take advantage of the disconnection mechanism. [1,8,37,55,57,144,172] For instance, the resistance shift in stretchable strain sensors made of Ti 3 C 2 T x MXene/CNTs films coated over the latex substrate was reported to be due to the changes in the overlapping areas and interconnecting pathways during cyclic stretching-releasing. [81] Similar behavior has been observed in the conductive network of Au nanosheets dropcast on the Ecoflex substrate.…”

“…Although cracks are undesirable for structural designs, the generation of microcracks in conductive thin films has been successfully utilized to develop highly sensitive strain sensors. The opening and enlargement of microcracks have been observed in CNT-based strain sensors, [109,138,173,174] graphene-based strain sensors and its derivatives, [6,57,117] metal NW-and NPs [86,116,[175][176][177][178][179][180] based strain sensors. The rapid separation of nanomaterials at the microcrack edges dramatically limits the electrical conduction paths within the thin films, leading to a significant increase in the electrical resistance of strain sensors under the applied tensile strain.…”

Recent advances in thermally activated delayed fluorescence for white OLEDs applications

“…In the design of device structure, exciton distribution should be precisely regulated, and the appropriate energy-level matching between each layer [169][170][171] and optical coupling technology [172][173][174] could help to increase the efficiency of devices. Many previous reports have claimed with suffering severe efficiency roll-off, which may be related to charge bal- ance, interlayer barriers, and slower RISC rate of TADF materials [175][176][177][178][179][180][181][182]. To loosen this bottleneck, the most important thing is to suppress the concentration quenching effect caused by triplet excitons.…”

Functionalized Fiber-Based Strain Sensors: Pathway to Next-Generation Wearable Electronics

“…Increased encapsulation thickness can guarantee good robustness but result in inconsistent compliance between encapsulation and sensing elements, which may deteriorate sensing reliability. Much research in recent years has focused on the relation between strain-caused cracks and the detection capability of strain sensors due to their outstanding sensitivity [145][146][147][148]. The unmatched mechanical properties between the fiber-based conductive elements and elastomers lead to functional cracks during strain deformation, further inducing the resistance increase.…”