The development of wearable strain sensors with simultaneous large stretchability (strain >55%) and high sensitivity (gauge factor >100) remains a grand challenge to this day. Drawing on inspiration from nature, nacre has demonstrated outstanding mechanical properties, especially combining high strength and toughness, which is due in part to its delicate hierarchical layered architecture with rich interfacial interactions. We demonstrate that strain sensors based on this nacre-mimetic microscale “brick-and-mortar” architecture can simultaneously achieve ultrahigh sensitivity and large stretchability while performing well in linearity, reliability, long-term durability, and monotonicity. The bioinspired sensor demonstrated a gauge factor >200 over a range of working strains up to 83% and achieved a high gauge factor exceeding 8700 in the strain region of 76–83%. This successful combination of high sensitivity and large stretchability is attributed to (1) the microscale hierarchical architecture derived fro...

Bioinspired Ultrasensitive and Stretchable MXene-Based Strain Sensor via Nacre-Mimetic Microscale "Brick-and-Mortar" Architecture.

High-energy all-in-one stretchable micro-supercapacitor arrays based on 3D laser-induced graphene foams decorated with mesoporous ZnP nanosheets for self-powered stretchable systems

Stretchable strain sensors based on conductive polymer composites commonly utilize elastic polymers as the matrix. However, elastic polymers always show strong mechanical hysteresis effect leading to shoulder peak phenomenon and thereby poor recoverability of strain sensors. Herein, we design a stretchable rough filament strain sensor with dentate groove structure to eliminate the shoulder peak phenomenon and improve recoverability. The filament strain sensor is fabricated by the extrusion of poly(styrene-b-ethylene-b-butylene-b-styrene) (SEBS) filament constructing dentate groove structure and the subsequent ultrasonic treatment decorating carbon nanotubes (CNTs) on the surface of the SEBS filament. It is interesting to find that the strain sensing range of rough SEBS/CNTs filaments with dentate groove structure is wider than that of smooth filaments. More importantly, the rough filament strain sensors exhibit significantly enhanced recoverability without shoulder peak during the releasing process while the rough dentate groove structure has minor effects on the mechanical properties of SEBS filaments. The great improvement is ascribed to the uniform distribution of deformation because of the dentate groove structure, which induces reduction of the mechanical hysteresis effect and thereby decreases residual strain. Moreover, the rough filament strain sensors have a favorable integration of good stability, fast response time of 300 ms (0.5% strain is applied with a high strain rate of 500 mm/min) and excellent durability (1976 cycles at the strain of 50%). The rough filament strain sensors can accurately and stably monitor both large and subtle human motions (such as body motion, expression and phonation), showing broad application prospects in wearable devices.

Stretchable strain sensors with dentate groove structure for enhanced sensing recoverability

High accuracy measurement of mechanical strain is critical and broadly practiced in several application areas including structural health monitoring, industrial process control, manufacturing, avionics and the automotive industry, to name a few. Strain sensors, otherwise known as strain gauges, are fueled by various nanomaterials, among which graphene has attracted great interest in recent years, due to its unique electro-mechanical characteristics. Graphene shows not only exceptional physical properties but also has remarkable mechanical properties, such as piezoresistivity, which makes it a perfect candidate for strain sensing applications. In the present review, we provide an in-depth overview of the latest studies focusing on graphene and its strain sensing mechanism along with various applications. We start by providing a description of the fundamental properties, synthesis techniques and characterization methods of graphene, and then build forward to the discussion of numerous types of graphene-based strain sensors with side-by-side tabular comparison in terms of figures-of-merit, including strain range and sensitivity, otherwise referred to as the gauge factor. We demonstrate the material synthesis, device fabrication and integration challenges for researchers to achieve both wide strain range and high sensitivity in graphene-based strain sensors. Last of all, several applications of graphene-based strain sensors for different purposes are described. All in all, the evolutionary process of graphene-based strain sensors in recent years, as well as the upcoming challenges and future directions for emerging studies are highlighted.

https://www.mdpi.com/2072-666X/13/1/119/pdf?version=1642063746

Graphene as a Piezoresistive Material in Strain Sensing Applications

This study demonstrates a scalable fabrication process for producing biodegradable, highly stretchable and wearable melt spun thermoplastic polypropylene (PP), poly(lactic) acid (PLA), and composite (PP:PLA = 50:50) conductive yarns through a dip coating process. Polydopamine (PDA) treated and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) coated conductive PP, PLA, and PP/PLA yarns generated electric conductivity of 0.75 S/cm, 0.36 S/cm and 0.67 S/cm respectively. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the interactions among the functional groups of PP, PLA, PP/PLA, PDA, and PEDOT:PSS. The surface morphology of thermoplastic yarns was characterized by optical microscope and Scanning Electron Microscope (SEM). The mechanical properties of yarns were also assessed, which include tensile strength (TS), Young’s modulus and elongation at break (%). These highly stretchable and flexible conductive PP, PLA, and PP/PLA yarns showed elasticity of 667%, 121% and 315% respectively. The thermal behavior of yarns was evaluated by differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Wash stability of conductive yarns was also measured. Furthermore, ageing effect was determined to predict the shelf life of the conductive yarns. We believe that these highly stretchable and flexible PEDOT:PSS coated conductive PP, PLA, and PP/PLA composite yarns fabricated by this process can be integrated into textiles for strain sensing to monitor the tiny movement of human motion.

Highly Stretchable and Flexible Melt Spun Thermoplastic Conductive Yarns for Smart Textiles.

Stretchable and wearable opto-electronics have attracted worldwide attention due to their broad prospects in health monitoring and epidermal applications. Resistive strain sensors, as one of the most typical and important device, have been the subject of great improvements in sensitivity and stretchability. Nevertheless, it is hard to take both sensitivity and stretchability into consideration for practical applications. Herein, we demonstrated a simple strategy to construct a highly sensitive and stretchable graphene-based strain sensor. According to the strain distribution in the simulation result, highly sensitive planar graphene and highly stretchable crumpled graphene (CG) were rationally connected to effectively modulate the sensitivity and stretchability of the device. For the stretching mode, the device showed a gauge factor (GF) of 20.1 with 105% tensile strain. The sensitivity of the device was relatively high in this large working range, and the device could endure a maximum tensile strain of 135% with a GF of 337.8. In addition, in the bending mode, the device could work in outward and inward modes. This work introduced a novel and simple method with which to effectively monitor sensitivity and stretchability at the same time. More importantly, the method could be applied to other material categories to further improve the performance.

/pdf/enhanced-stretchable-and-sensitive-strain-sensor-via-1f8krgm9wt.pdf

Enhanced Stretchable and Sensitive Strain Sensor via Controlled Strain Distribution.

A large bandwidth and high-efficiency subwavelength quarter-wave plate (QWP) is an indispensable component of an integrated miniaturized optical system. The bandwidth of existing plasmonic quarter-wave plates with a transmission efficiency of more than 50% is less than 320 nm in the near-infrared band. In this paper, a metallic quarter-wave plate with a bandwidth of 600 nm (0.95–1.55 µm) and an average transmittance of more than 70% has been designed and shows excellent potential to be used in miniaturized optical polarization detection systems and as an optical data storage device. For TE mode incident waves, this miniaturized optical element can be equivalent to a Fabry-Perot (FP) resonator. Meanwhile, for the TM mode incident wave, the transmission characteristics of this structure are controlled by gap surface plasmon polaritons (G-SPPs) existing in the symmetric metal/insulator/metal (MIM) configuration.

Large bandwidth and high-efficiency plasmonic quarter-wave plate.

2.X μm InGa(As)Sb/AlGaAsSb compressively strained quantum wells laser has been grown and fabricated. Antimonide laser with 1.5mm*90μm without AR/HR emitted 550mW of continuous wave output power at 2μm.And 2.4μm laser without AR/HR output 195mW at room temperature.

Chuanchuan Li

Papers

Enhanced Stretchable and Sensitive Strain Sensor via Controlled Strain Distribution.

Large bandwidth and high-efficiency plasmonic quarter-wave plate.

MBE growth and fabrication of 2.Xμm InGa(As)Sb/AlGaAsSb laser