scholarly journals Self-Healing Mechanism and Conductivity of the Hydrogel Flexible Sensors: A Review

Gels ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 216
Author(s):  
Juan Zhang ◽  
Yanen Wang ◽  
Qinghua Wei ◽  
Yanmei Wang ◽  
Mingju Lei ◽  
...  

Sensors are devices that can capture changes in environmental parameters and convert them into electrical signals to output, which are widely used in all aspects of life. Flexible sensors, sensors made of flexible materials, not only overcome the limitations of the environment on detection devices but also expand the application of sensors in human health and biomedicine. Conductivity and flexibility are the most important parameters for flexible sensors, and hydrogels are currently considered to be an ideal matrix material due to their excellent flexibility and biocompatibility. In particular, compared with flexible sensors based on elastomers with a high modulus, the hydrogel sensor has better stretchability and can be tightly attached to the surface of objects. However, for hydrogel sensors, a poor mechanical lifetime is always an issue. To address this challenge, a self-healing hydrogel has been proposed. Currently, a large number of studies on the self-healing property have been performed, and numerous exciting results have been obtained, but there are few detailed reviews focusing on the self-healing mechanism and conductivity of hydrogel flexible sensors. This paper presents an overview of self-healing hydrogel flexible sensors, focusing on their self-healing mechanism and conductivity. Moreover, the advantages and disadvantages of different types of sensors have been summarized and discussed. Finally, the key issues and challenges for self-healing flexible sensors are also identified and discussed along with recommendations for the future.

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Hüsnügül Yılmaz Atay ◽  
Leyla Eral Doğan ◽  
Erdal Çelik

Chitosan has a very wide application range in different parts of life such as in biomedical and antimicrobial areas. In recent years the self-healing property of chitosan becomes more of an issue. In the study chitosan was used to obtain a self-healing composite material. An epoxy dye was converted to a self-healing coating. Different types of samples were prepared by coating the glass substrates with a polymer matrix reinforced with various amounts of chitosan. The samples were characterized by fourier transform Infrared (FTIR) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS). In addition, self-healing test was applied as a primary objective of this research. In this respect, the samples were scratched with a very thin pin, and they were analyzed by SEM periodically. It was observed that chitosan-reinforced dyes showed self-healing property. Mechanism of the self-healing process was also scrutinized.


Author(s):  
K. Rudi ◽  
D. H Andrew ◽  
R. Managam ◽  
Zainuddin Nawawi ◽  
Naohiro Hozumi ◽  
...  

2018 ◽  
Vol 932 ◽  
pp. 57-61
Author(s):  
Wei Sun ◽  
Rong Xin Yan ◽  
Li Chen Sun ◽  
Zheng Li ◽  
Guan Qing Lang ◽  
...  

It is great significance to study self-healing aluminum alloy materials for spacecraft the structure protection from high energy space weapon attack and debris impact in future. In this paper, Using aluminum alloy (6063) as matrix material with low melting point alloy (Sn60Pb40, the melting point of 183°C) as repairing materials, the self-healing Aluminum Alloy material was designed and manufactured by the smelting and casting method. The crack damage repair performance of the self-healing Al alloy was researched through the experiment. The results show that the self-healing aluminum alloy has certain self-healing ability without help, when the temperature reaches the melting point temperature of Sn60Pb40. The repair time is about 20min, the crack filling rate can reach 84%. The research conclusion can provide a reference for the development of metal self-healing material technology.


2015 ◽  
Vol 40 (21) ◽  
pp. 5066 ◽  
Author(s):  
Liyun Zhang ◽  
Fengjuan Ye ◽  
Mingtao Cao ◽  
Dong Wei ◽  
Pei Zhang ◽  
...  

2021 ◽  
Vol 9 ◽  
Author(s):  
Feng Ji ◽  
Min Jiang ◽  
Qingyu Yu ◽  
Xuefang Hao ◽  
Yan Zhang ◽  
...  

Currently, stretchable hydrogel has attracted great attention in the field of wearable flexible sensors. However, fabricating flexible hydrogel sensor simultaneously with superstretchability, high mechanical strength, remarkable self-healing ability, excellent anti-freezing and sensing features via a facile method remains a huge challenge. Herein, a fully physically linked poly(hydroxyethyl acrylamide)-gelatin-glycerol-lithium chloride (PHEAA-GE-Gl-LiCl) double network organohydrogel is prepared via a simple one-pot heating-cooling-photopolymerization method. The prepared PHEAA-GE-Gl-LiCl organohydrogel exhibits favorable stretchability (970%) and remarkable self-healing property. Meanwhile, due to the presence of glycerol and LiCl, the PHEAA-GE-Gl-LiCl organohydrogel possesses outstanding anti-freezing capability, it can maintain excellent stretchability (608%) and conductivity (0.102 S/m) even at −40°C. In addition, the PHEAA-GE-Gl-LiCl organohydrogel-based strain sensor is capable of repeatedly and stably detecting and monitoring both large-scale human motions and subtle physiological signals in a wide temperature range (from −40°C to 25°C). More importantly, the PHEAA-GE-Gl-LiCl organohydrogel-based sensor displays excellent strain sensitivity (GF = 13.16 at 500% strain), fast response time (300 ms), and outstanding repeatability. Based on these super characteristics, it is envisioned that PHEAA-GE-Gl-LiCl organohydrogel holds promising potentials as wearable strain sensor.


Coatings ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 421 ◽  
Author(s):  
Lei Peng ◽  
Musong Lin ◽  
Sheng Zhang ◽  
Li Li ◽  
Qiang Fu ◽  
...  

A self-healing coating with UV-shielding property was prepared in this paper. The self-healing property was based on the inclusion between a host (β-CD-TiO2) and a guest HEMA-Ad). After inclusion of the host and guest, the host–guest complex (HEMA-Ad/β-CD-TiO2) was polymerized with other reactive monomers (HEMA and BA) to obtain the final coating. The coating had good hydrophobicity (water contact angle >90°, moisture absorption rate <2%) and excellent UV-shielding performance (ultra-violet protect factor >90%), and could be firmly bonded to a soft substrate. In addition, the coating had good self-healing property, which means that cracks in the material can recover many times after being damaged and that the UV-shielding ability can be fully restored with the self-healing process.


Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 490 ◽  
Author(s):  
Haifeng Zhao ◽  
Heng An ◽  
Baozhong Xi ◽  
Yan Yang ◽  
Jianglei Qin ◽  
...  

Self-healing hydrogels have drawngreat attention in the past decade since the self-healing property is one of the characteristics of living creatures. In this study, poly(acrylamide-stat-diacetone acrylamide) P(AM-stat-DAA) with a pendant ketone group was synthesized from easy accessible monomers, and thermo-responsive self-healing hydrogels were prepared through a series of diacylhydrazide compounds cross-linking without any additional stimulus. Although the copolymers do not show thermo-response, the hydrogels became thermo-responsive andboth the lower critical solution temperature (LCST) and upper critical solution temperature (UCST) varied with the composition of the copolymer and structure of cross-linkers. With a dynamic covalent bond connection, the hydrogel showed gel-sol-gel transition triggered by acidity, redox, and ketone to acylhydrazide group ratios. This is another interesting cross-linking induced thermo-responsive (CIT) hydrogel with different properties compared to PNIPAM-based thermo-responsive hydrogels. The self-healing hydrogel with CIT properties could have great potential for application in areas related to bioscience, life simulation, and temperature switching.


2014 ◽  
Vol 50 (18) ◽  
pp. 2356-2359 ◽  
Author(s):  
Shibaji Basak ◽  
Jayanta Nanda ◽  
Arindam Banerjee

Self-healable, multi-stimuli responsive metallo-hydrogels based on a series of tyrosine containing amphiphiles have been discovered. Formation of these metallo-gels is highly selective to Ni2+ ions. Moreover, the self-healing property can be modulated by varying the chain length of the corresponding gelator amphiphiles.


Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1194
Author(s):  
Nik Nur Farisha Nik Md Noordin Kahar ◽  
Azlin Fazlina Osman ◽  
Eid Alosime ◽  
Najihah Arsat ◽  
Nurul Aida Mohammad Azman ◽  
...  

The versatility of polymeric materials as healing agents to prevent any structure failure and their ability to restore their initial mechanical properties has attracted interest from many researchers. Various applications of the self-healing polymeric materials are explored in this paper. The mechanism of self-healing, which includes the extrinsic and intrinsic approaches for each of the applications, is examined. The extrinsic mechanism involves the introduction of external healing agents such as microcapsules and vascular networks into the system. Meanwhile, the intrinsic mechanism refers to the inherent reversibility of the molecular interaction of the polymer matrix, which is triggered by the external stimuli. Both self-healing mechanisms have shown a significant impact on the cracked properties of the damaged sites. This paper also presents the different types of self-healing polymeric materials applied in various applications, which include electronics, coating, aerospace, medicals, and construction fields. It is expected that this review gives a significantly broader idea of self-healing polymeric materials and their healing mechanisms in various types of applications.


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