Electrospining: Bioinspired Ultrasensitive Flexible Strain Sensors for Real‑Time Wireless Detection of Liquid Leakage

On 23 October, 2024, Academician Qu Jinping, Associate Professor Ting Wu from Huazhong University of Science and Technology, Heng Xie from Wuhan University of Technology, and Professor Jinlian Hu from City University of Hong Kong published a new research paper in Nano-Micro Letters (impact factor: 31.6), " Bioinspired Ultrasensitive Flexible Strain Sensors for Real‑Time Wireless Detection of Liquid Leakage ". The sensor combines micro-extrusion compression molding and surface modification technology for real-time wireless detection of liquid leaks.

【Method】

The researchers focused on a biomimetic super-hydrophobic thermoplastic polyurethane/carbon nanotube/graphene nanosheet flexible strain sensor (TCGS). TCGS utilizes the synergistic effect of Archimedean spiral crack arrays and micropores, and this design is inspired by the excellent perception ability of scorpions. The design achieved a sensitivity of 218.13 at a strain of 2%, an increase of 4300%. In addition, TCGS showed excellent durability and was able to withstand more than 5,000 cycles of use.

【Research innovation】

Source of inspiration and sensor development: Inspired by the excellent sensing capabilities of organisms in nature (especially scorpions), a bio-inspired ultra-sensitive flexible strain sensor was developed. Scorpions rely on their highly developed and sensitive sensing mechanisms to adapt to harsh environments, which provides inspiration for sensor design.

TCGS design and manufacturing: The sensor (TCGS) adopts an innovative manufacturing method that combines micro-extrusion compression molding (μ-ECM) and surface modification. TCGS combines thermoplastic polyurethane (TPU), carbon nanotubes (CNTs) and graphene nanosheets (GNS) and is cost-effective, easy to operate and suitable for mass production. The sensor replicates the scorpion's advanced sensing mechanism, using micropores and cracks to deform when subjected to forces in different directions, thereby changing resistance and providing a highly sensitive electrical response.

Superior sensor performance and features: TCGS has a super-hydrophobic conductive surface design, which significantly improves the efficiency and stability of detecting liquid leakage in humid environments. The sensor utilizes the synergistic effect of micropores and Archimedean spiral cracks to achieve a sensitivity of 218.13 at 2% strain, an increase of 4300%. The sensor has excellent durability and is able to withstand over 5,000 cycles of use. The superhydrophobic properties of TCGS effectively prevent liquid adhesion and maintain high sensitivity and stability even in humid environments.

Application and real-time detection: Integrating TCGS into leak detection equipment enables real-time wireless monitoring of liquid leaks of various sizes, speeds and compositions. Leak detection equipment can cover the range from droplets to high flow leaks and issue corresponding real-time alerts. The equipment can be widely used in pipeline networks to quickly respond to leaks and prevent resource losses while significantly reducing safety hazards and promoting sustainable development. 

【Graphic Explanation】

figure 1. Schematic illustrations of TCGS inspired by the scorpion sensory system. a Scorpions possess ultrasensitive crack organs that help them perceive external forces and vibrations. The enlarged image depicts the sensory system, which consists of crack arrays, numerous cells, and neurons. b Illustration showing the preparation procedure of TCGS. c Application of TCGS in real-time wireless detection of liquid leakage

figure 2. Microscopic morphology and characterization of TCGS. a A square TC-1 supported by a pink flower. b TC-1 shown before and after immersion in deionized water for 12 h. c FTIR spectra. d XRD patterns of TC-0, TC-0.5, TC-1, TC-1.5, and CNTs. e Tensile stress–strain curves. f Tensile strength and elongation at break for TC foams. g Pore size distribution of TC foams. h Cross-sectional SEM images of TC-1. i Enlarged view of h, j, k Surface SEM images of TCGS-7. l Cross-section SEM images and m elemental distribution of TCGS-7. n Laser scanning confocal microscopy image. o XPS survey spectra of GNS, TC-1, and TCGS-7. p C 1s XPS spectrum of TCGS-7

figure 3. Working mechanism and performance of TCGS. a Resistance changes within the strain range of 0 to 2%. b ΔR/R0-strain curves at 0.1%, 0.2%, 0.3%, 0.5%, 0.7%, 0.9%, and 1% strain. c ΔR/R0-strain curves under various applied frequencies at 0.3% strain. d Response and recovery times under 0.2% strain. e Long-term stability over 5000 cycles at 0.3% strain. f FEA simulations for models with N of 0, 3, 5, and 7. g Displacement changes under different pressures for the model with N = 7. h Stress distribution and current density modulus distribution within the micropore-crack synergistic structure under various strains. i Comparison of the sensitivity of flexible strain sensors recently reported in the literature with our sensor

figure 4. Analysis of sensor properties including static wettability, dynamic wettability, and electric response signals for various liquid droplets. a Analysis of CA, RA, and static wettability. b Selected snapshots showing droplets impacting the TCGS-7 surface at velocities of 0.77 and 0.99 m s −1, incorporating dynamic wettability analysis. c Electrical responses to water droplets of different sizes dropped from a height of 30 cm, including linear analysis. d Electrical responses to 70 μL water droplets falling from varied heights, with linear analysis. e Response to various compositions of water droplets: tap water, acidic (pH=4), alkaline (pH=10), 5% saline, and 5% mud solutions. f Analysis of CA, RA, and the electrical responses of droplets in solutions with varying pH levels, salt concentrations, and mud contents. g Long-term detection of electrical response signals from water droplets

figure 5. Applications of TCGS-based leakage detection device. a Overview of pipe distribution and leakage beneath the city (left), an enlarged view of different pipe leakages (center), and the components of TCGS-based leakage detection device (right). b Liquid leakage detection process: from a normal state, to water droplet leakage, small water flow leakage, large water flow leakage, and finally, to recovery. c Design of the hardware for leakage detection. d Design of the software. e Response signals for normal state, droplet leakage, small flow leakage, large flow leakage. f Leakage detection for various liquids: acidic (pH=5), alkaline (pH=10), saline (5% concentration), and mud (5% concentration)

The TCGS leak detection device with excellent sensitivity and stability has been successfully developed, which can accurately detect and provide warnings of liquid leaks. TCGS uses the synergy of micropores and Archimedean spiral cracks and has multiple advantages, including high cost-effectiveness, high sensitivity, high stability, super hydrophobicity, quantitative detection capabilities, and real-time wireless detection capabilities. The device has shown practical value in preventing global liquid leaks and promoting sustainable development, and has excellent environmental adaptability and scalability.

link：

https://link.springer.com/article/10.1007/s40820-024-01575-2