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10.3390/mi14040876 5 Li B., Sun H., Zhang H., Li Y., Zang J., Cao X., Zhu X., Zhao X., Zhang Z. Refractive Index Sensor Based on the Fano Resonance in Metal-Insulator-Metal Waveguides Coupled with a Whistle-Shaped Cavity. 35744454 23 Li J., Zhang Z., Zhu X., Zhao Y., Ma Y., Zang J., Li B., Cao X., Xue C. Automatic Classification Framework of Tongue Feature Based on Convolutional Neural Networks. 36014231 14 Su Y., Ma K., Yuan F., Tang J., Liu M., Zhang X. High-Performance Flexible Piezoresistive Sensor Based on Ti3C2Tx MXene with a Honeycomb-like Structure for Human Activity Monitoring. 10.3390/mi13071153 7 Gao R., Zhang W., Jing J., Liao Z., Zhao Z., Yao B., Zhang H., Guo Y., Xu Y., Wang Y. Design, Fabrication, and Dynamic Environmental Test of a Piezoresistive Pressure Sensor. [Extracted from the article]

Flexible pressure sensors play an important role in flexible robotics, human-machine interaction (HMI), and human physiological information. However, most of the reported flexible pressure sensors suffer from a highly nonlinear response and a significant decrease in sensitivity at high pressures. Herein, we propose a flexible novel iontronic pressure sensor based on monolayer molybdenum disulfide (MoS2). Based on the unique structure and the excellent mechanical properties as well as the large intercalation capacitance of MoS2, the prepared sensor holds an ultra-high sensitivity (Smax = 89.75 kPa−1) and a wide sensing range (722.2 kPa). Further, the response time and relaxation time of the flexible sensor are only 3 ms, respectively, indicating that the device can respond to external pressure rapidly. In addition, it shows long-term cycling stability (over 5000 cycles with almost no degradation) at a high pressure of 138.9 kPa. Finally, it is demonstrated that the sensor can be used in physiological information monitoring and flexible robotics. It is anticipated that our prepared sensor provide a reliable approach to advance the theory and practicality of the flexible sensor electronics. [ABSTRACT FROM AUTHOR]

[Display omitted] The significant advancement in 2D materials fabrications has ushered a paradigm shift in material chemistry, which in turn has greatly influenced the manufacturing industries, in terms of products offered to the global community. The development of smart flexible electronics is one of such advancements, with remarkable potentials when intelligently understood and applied. This review aims to provide an up-to-date survey of significant flexible electronics manufactured using 2D materials, analyze the additive manufacturing processes involved, anatomize inks formulation processes, properties, and post-treatment necessary for further advancement in smart flexible manufacturing. Finally, some explicit description of various smart applications of 2D materials inks in batteries, micro-supercapacitors, sensors, and other flexible electronics are highlighted, along with enlightening futuristic glimpse into their innovative integration into soft robotics. [ABSTRACT FROM AUTHOR]

Flexible transparent conductive films are indispensable for nowadays wearable electronic devices with various applications. However, existing solutions such as ITO and metal mesh were limited by their poor intrinsic stretching ability. In this work, we designed and fabricated silver nanowires (AgNWs) on graphene hybrid films for enhanced mechanical and electrical performance. In situ TEM characterizations show that, beside conductive paths, silver nanowire network, can also contribute to the toughening mechanisms of the hybrid films. Furthermore, bending and electrical tests were applied to examine the corresponding flexible electronics' performance. Finally, we showed that the fabrication of our AgNW/graphene hybrid films could be scaled up for large film applications and extended to other 1D/2D hybrid systems. [ABSTRACT FROM AUTHOR]

The sp2 nature of graphene endows the hexagonal lattice with very high theoretical stiffness, strength and resilience, all well-documented. However, the ultimate stretchability of graphene has not yet been demonstrated due to the difficulties in experimental design. Here, directly performing in situ tensile tests in a scanning electron microscope after developing a protocol for sample transfer, shaping and straining, we report the elastic properties and stretchability of free-standing single-crystalline monolayer graphene grown by chemical vapor deposition. The measured Young's modulus is close to 1 TPa, aligning well with the theoretical value, while the representative engineering tensile strength reaches ~50-60 GPa with sample-wide elastic strain up to ~6%. Our findings demonstrate that single-crystalline monolayer graphene can indeed display near ideal mechanical performance, even in a large area with edge defects, as well as resilience and mechanical robustness that allows for flexible electronics and mechatronics applications. The extraordinary mechanical properties of graphene are usually measured on very small or supported samples. Here, the authors develop a method to test a large area of graphene and show that even with edge defects it displays near-ideal mechanical performance. [ABSTRACT FROM AUTHOR]

Flexible graphene field effect transistors (GFETs) are fabricated on a polyimide (PI) substrate by an improved self‐aligned fabrication procedure. Short gate length of 50 nm is achieved. Ohmic contact resistance is depressed. The prepared GFET shows comparable intrinsic cut‐off frequency and maximum oscillation frequency of 116 and 110 GHz, respectively. The high frequency of flexible GFET demonstrated here paves the way for applications which require high flexibility and radio frequency operations. Graphene has great application potential in the evolution of next generation flexible electronics. In this work, flexible graphene field effect transistors (GFETs) with very short gate‐length of 50 nm were fabricated on a polyimide (PI) substrate. The GFET demonstrates an extrinsic fT of 56 GHz, which is the highest extrinsic fT achieved in flexible GFETs reported to date. [ABSTRACT FROM AUTHOR]

The high demand for flexible force sensors with both strain and pressure sensing has attracted considerable attention for various application scenarios, such as electronic skins and smart prostheses. However, successful application of these sensors in real-world is challenging because the performance of the sensors can be severely degraded under applied off-axial deformations (e.g., bending and twisting) and it is also difficult to successfully decouple these signals due to electromechanical crosstalk. Here, we developed an integrated sensor patch (ISP) consisting of a strain sensor insensitive to pressure, bending and twisting, coupled with a pressure sensor insensitive to tension, bending and twisting. Benefiting from the serpentine structure and bionic design of strain sensor material, as well as the inherent rigidity properties of the piezoelectric ceramic, the resulting patch exhibits insensitivity to off-axis sensing with independent tensile strain and out-of-plane pressure sensing capabilities. The patch achieves a wide range of tensile strains (up to 160% with an apparent pressure coefficient of over 1.23) and a wide range of pressures (1 Pa to 100 kPa). We demonstrate that the wearable ISP can interact human gestures with the robotic hand in real time through a fully soft integrated glove and further continuously record wrist activity to verify tensile strain sensing independent of pressure mode. In addition, the ISP successfully captures the subtle strain of less than 20% of eye blinks and the ultra-low pressure of less than 1.2 kPa of unobtrusive exhalation force with low off-axis interference. Moving forward, this strategy of endowing sensors with off-axis sensing insensitivity and decoupled strain and pressure sensing has great potential in human-machine interface (HMI), virtual reality (VR)/augmented reality (AR) user interfaces, and other soft electronics fields. [Display omitted] • The flexible sensor can independently detect both tensile strain and pressure. • The sensor is insensitive to off-axis deformation, such as bending and twisting. • The sensor can accurately interact with human and monitor the vital signal. [ABSTRACT FROM AUTHOR]

Developing a generalized route to effectively fabricate periodic mechanically flexible graphene aerogels across several size orders and whole structural integrity on a large scale for flexible electronics is still a challenge. Herein, inspired by bamboo's natural hierarchical structure, a general method is developed to effectively fabricate biomimetic cellular graphene fibers using hydrogen bubbles and ice simultaneously as templates, whose whole size ranges from micro to several centimeters. Owing to its superior mechanical flexibility demonstrated by the in situ scanning electron microscope test and intrinsically good electrical conductivity, its potential in flexible electronics such as sensors, supercapacitors, and Ni–Zn batteries is carefully investigated. It not only shows superior sensitivity in the monitoring of the pulse pressure in sensor devices but also directly serves as a promising binder, flexible scaffold, and conductive additive, as well as extra active material in the energy storage device without any extra additives. This strategy can also be extended to fabricate other configurations of graphene aerogels such as spring‐like type and bulk film, able to serve as the next generation of intelligent infrastructure for achieving multifunctional structural and functional tasks. [ABSTRACT FROM AUTHOR]

• The sensor achieves favorable trade-off between sensitivity (S max > 450 kPa−1) and sensing range (250 kPa). • The sensor shows an excellent self-cleaning attribute. • Flexible circuit board was successfully integrated with the sensor to transmit the force signal. A wearable integrated tactile sensory system consisting of self-cleaning flexible pressure sensors with ultrahigh sensitivity (S max > 450 kPa−1) and flexible circuit board can wirelessly transmit the force signals. [Display omitted] Flexible tactile sensors (FTS), which have been extensively used in force sensing devices, are gaining tremendous attentions in various application fields, such as robots, electronic skin (E-Skin), human-machine interaction (HMI), and many other rapidly developing frontier technologies. However, fabricating FTS achieving both high sensitivity and broad sensing range remains a great challenge. Moreover, the integration of FTS with flexible circuit boards has long been a hot topic due to its potential applications in flexible hybrid electronics (FHEs). Here, we report a novel flexible tactile sensor with ultrahigh sensitivity and wide sensing range and its application in a self-cleaning and fully integrated wearable tactile sensing system for real-time analysis. Benefiting from the conductive sensing materials composed of fine inverted pyramid arrays and double-covered sensing layers, the sensor exhibits a superior sensitivity of 451.292 kPa−1, a wide working range up to 250 kPa, and a fast response time of 31 ms, as well as long-term durability. Furthermore, the sensor system can accurately monitor the grasped force in real-time and easily be fixed on a flexible clamping jaw or human hands. Our design concept and experimental approach, either for the flexible sensor or the whole system, potentially push further the wearable electronics toward practical applications. [ABSTRACT FROM AUTHOR]