| Author: | Tian, Xiao |
| Title: | Study of multifunctional one-, two- and three-dimensional fiber-based triboelectric nanogenerators and self-powered sensors |
| Advisors: | Hua, Tao (SFT) |
| Degree: | Ph.D. |
| Year: | 2023 |
| Subject: | Nanoelectronics Nanotechnology Electronic textiles Wearable technology Hong Kong Polytechnic University -- Dissertations |
| Department: | School of Fashion and Textiles |
| Pages: | xxvi, 235 pages : color illustrations |
| Language: | English |
| Abstract: | With the development of the Internet of Things (IoTs), wearable electronics which can meet the requirements of flexibility and lightweight have attracted long-lasting attentions. However, in order to power wearable electronics, conventional energy storage units such as batteries and capacitors are typically employed, which have limitations such as heavy weight, bulky volume, limited lifetime and requiring recharging by the immobile power plants. The triboelectric nanogenerator (TENG) is a newly developed energy harvesting technology that can effectively convert biomechanical energy into electrical energy. By virtue of its low cost, simple structure and environmental friendliness as well as easy fabrication, integration of TENG with conventional textiles paves a new avenue for wearable electronics. Up to now, a variety of textile-based triboelectric nanogenerators (t-TENGs) with numerous materials, various structures and fabrication techniques have been developed. However, it is still challenging to fabricate high-performance t-TENGs with good electrical properties, wearability and functionality by continuous fabrication technologies. To address these challenges, this thesis focuses on designing and developing flexible and wearable t-TENGs based on the synergistic effect of fiber materials, structures and textile engineering. Four types of t-TENGs, including one-dimensional (1D) PVDF yarn-based textile triboelectric nanogenerator, 1D core-spun yarn structured triboelectric nanogenerator based on chitosan/Tencel fibers, two-dimensional (2D) triboelectric nanogenerator fabric and three-dimensional (3D) woven structured triboelectric nanogenerator fabric, were developed. Firstly, since 1D fiber/yarn-based t-TENGs are easily extensible, a 1D braiding-structured triboelectric yarn (BYTENG) fabricated by a polyamide (PA) conductive yarn and wet-spun poly (vinylidene fluoride) (PVDF) yarn has been designed and developed by scalable wet spinning and braiding technologies for energy harvesting and biomechanical sensing. Owing to unique material and structural configuration, the BYTENG possesses the merits of mechanical robustness and flexibility. The BYTENG exhibits good machine washability and sensing performance, with a wide working range from 7 kPa to 127 kPa and a relatively high pressure sensitivity of 0.2V kPa−1. More importantly, compared with PVDF electrospun films, this structure has better integration capability and can be used in sports products for real-time exercise detection. Furthermore, knitted and woven triboelectric fabrics (FTENGs) fabricated by the as-prepared BYTENG not only possess excellent air permeability but also can be applied to the seat cushion, backrest or carpet for human motion monitoring. This work greatly promotes the numerous applications of the t-TENGs and contributes to the further development of wearable electronics. In order to further improve the functionality, biodegradability and compatibility with textile technology of 1D triboelectric yarn, an extremely durable and eco-friendly 1D core-spun structured triboelectric yarn (CYTENG) as a composite yarn has been developed by a scalable fancy spinning twister technology, which was made of PA conductive yarn (core yarn) and Tencel-chitosan blended yarn (wrapping yarn). The as-prepared CYTENG possesses the characteristics of high softness, small diameter, low weight and cost, high scalability and productivity. A voltage with value of 14.2 V and a current of 0.8 µA can be obtained from the CYTENG with the length of 45 cm under impacting frequency of 3 HZ and force of 100 N. A smart glove with sewed CYTENGs was fabricated, which can be used to monitor various gesture signals. Subsequently, a novel 2D triboelectric fabric (FTENG) with woven structure was fabricated based on continuously spun CYTENG by automatic weaving machine, which overcame the problems of complicated manufacturing process, high cost, poor comfort and small-scale production. A desirable open-circuit voltage of 31.3 V and a short-circuit current of 1.8 µA as well as instantaneous power density of 15.8 mW/m2 under a load resistance of 70 MΩ are realized by the prepared FTENG with the size of 5 × 5 cm2. Besides, the FTENG performs excellent wearability and comfort, such as high flexibility, desirable breathability and good machine washability. Moreover, the FTENG exhibits excellent antibacterial property, wherein the inhibition rates against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Candida albicans (C. albicans) can reach up to 99%. Furthermore, it can be used as a self-powered sensor, wherein the developed FTENG can be attached under the arm and foot to demonstrate the ability to detect different body movements. At last, based on a rational design of material system and structure, a multifunctional 3D triboelectric nanogenerator fabric (3D SP-FTENG) was designed and developed, which was composed of three layers, including the inner polypropylene (PP)-cotton fabric layer close to skin for moisture transfer and absorption, the middle Ag-cotton fabric layer for conducting electrode and antibacterial agent, and the outer PTFE-cotton fabric layer for tribo-negative layer and repelling water, respectively. The 3D SP-FTENG performs excellent electrical output (27.33 V, 1.76 µA and 61.6 mW/m2) and wearability (directional water transport and breathability) as well as antibacterial activity. The geometric models of the functional zones of the 3D FTENGs are proposed to explain the electrical output and directional water transport performance. Moreover, in contrast to the previously reported multilayer t-TENGs which were constructed by directly stacking multilayer functional fabrics together, the fabric interface of this new structure is not easily delaminated through weaving the support area and the functional area together. The 3D SP-FTENG demonstrates outstanding durability such as machine washability and ultrahigh abrasion resistance. In addition, the SP-FTENG is able to drive wearable electronics and be used as a self-powered sensor, such as constantly monitoring the movement signals of human body. In summary, this thesis carried out a systematic research on developing fully textile-based TENGs including 1D yarn-based TENGs, 2D fabric-based TENG and 3D fabric-based TENG by utilizing the synergistic effect of fiber materials, structures and textile engineering. Various types of flexible t-TENGs have been successfully demonstrated. Such t-TENGs exhibit satisfactory electrical output performance, excellent integration ability and functionality as well as wearability. This study opens a new avenue to combine economically available materials and current textile technologies for fabricating t-TENGs with flexible yarn/fabric structures that are promising to promote the commercialization of smart energy garments. Moreover, fabrication and integration strategies reported in this thesis can not only achieve the desired electrical properties, but also maintain the inherent advantages of the textile, which contribute to the further development of t-TENGs for the self-powered sensor applications. |
| Rights: | All rights reserved |
| Access: | open access |
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