Mechanical energy harvesting and self-powered electronic applications of textile-based piezoelectric nanogenerators: a systematic review

Environmental pollution resulting from fossil fuel consumption and the limited lifespan of batteries has shifted the focus of energy research towards the adoption of green renewable technologies. On the other hand, there is a growing potential for small, wearable, portable electronic devices. Therefore, considering the pollution caused by fossil fuels, the drawbacks of chemical batteries, and the potential applications of small-scale wearables and portable electronic devices, the development of a more effective lightweight power source is essential. In this context, piezoelectric energy harvesting technology has attracted keen attention. Piezoelectric energy harvesting technology is a process that converts mechanical energy into electrical energy and vice-versa. Piezoelectric energy harvesters can be fabricated in various ways, including through solution casting, electrospinning, melt spinning, and solution spinning techniques. Solution and melt-spun filaments can be used to develop woven, knitted, and braided textile-based piezoelectric energy harvesters. The integration of textile-based piezoelectric energy harvesters with conventional textile clothing will be a key enabling technology in realising the next generation smart wearable electronics. This review focuses on the current achievements on textile based piezoelectric nanogenerators (T-PENGs), basic knowledge about piezoelectric materials and the piezoelectric mechanism. Additionally, the basic understanding of textiles, different fabrication methods of T-PENGs, and the strategies to improve the performance of piezoelectric nanogenerators are discussed in the subsequent sections. Finally, the challenges faced in harvesting energy using textile based piezoelectric nanogenerators (T-PENGs) are identified, and a perspective to inspire researchers working in this area is presented

Wearable nanocomposite textile-based piezoelectric and triboelectric nanogenerators: progress and perspectives

In recent years, the widespread adoption of next-generation wearable electronics has been facilitated by the integration of advanced nanogenerator technology with conventional textiles. This integration has led to the development of textile-based nanogenerators (t-NGs), which hold tremendous potential for harvesting mechanical energy from the surrounding environment and serving as power sources for self-powered electronics. Textile structures are inherently flexible, making them well-suited for wearable applications. However, their electrical performance as nanogenerators is significantly limited when used without any modifications. To address this limitation and enhance the electrical performance of textile-based nanogenerators, nanocomposite textiles have been extensively utilized for fabricating advanced nanogenerators. This critical review focuses on the recent progress in wearable nanocomposite textiles-based piezoelectric and triboelectric nanogenerators. The review covers the fundamentals of piezoelectricity and triboelectricity, the working principles of nanogenerators, and the selection of materials. Furthermore, it provides a detailed discussion of nanocomposite textiles in various forms, such as fibers or yarns, fabrics, and electrospun nanofibrous webs, which are employed in piezoelectric and triboelectric nanogenerators. The review also highlights the challenges associated with their implementation and outlines the prospects of textile-based nanogenerators. It can be concluded that nanocomposite textile based piezoelectric and triboelectric nanogenerators exhibit better electrical output and mechanical strength compared to conventional textile based nanogenerators. Nanocomposite electrospun web based piezoelectric nanogenerators exhibit higher piezoelectric output compared with nanocomposite fibre/yarn or fabric based piezoelectric nanogenerators. This is because an in-situ poling takes place in electrospinning unlike with fibre or fabric based piezoelectric nanogenerators. Nanocomposite electrospun web based triboelectric nanogenerators also show better triboelectric output compared to the fibre or fabric-based equivalents. This is due to the higher contact area developed with electrospun nanocomposite webs compared to the fibre or fabric cases. Overall, it can be concluded that while nanocomposite construction can boost output and durability of textile based nanogenerators, more research is required to bring output, stability and durability up to the levels achievable with non-textile based devices

Investigating the Combined Effect of Natural and Metal Salt Mordants on Coloring Potential of Indian Rhubarb (Rheum emodi) Natural Dye

Synthetic dyes produce wide range of shades, but some of them especially azo dyes have been recently discovered to cause severe human health and environmental problems. This has motivated research activities in the exploitation of dyes from natural products for the coloration of different textile materials. In the present investigation, Indian rhubarb (Rheum emodi) was used as a source of natural dye for the development of deep and bright shades on premordanted woollen yarn samples. Dyeing experiments were carried on wool samples pretreated with different combinations of natural and chemical mordants such as 2.5% myrobalan + 10% alum, 2.5% myrobalan + 2% iron, and 2.5% myrobalan + 0.5% tin. The light, wash, and rub fastness properties of dyed woollen yarn samples were evaluated along with the determination of lightness (L*), chroma (c*), hue angle (h°), and strength (K/S) values using 8% concentration of Indian rhubarb dye

Dyeing of wool with the extract of henna leaves using mixed metal mordants

Woollen yarns have been dyed with colourant extracted from henna (Lawsonia inermis) leaves, in the absence and presence of mixed metal mordants for producing shades of different colours ranging from orange-yellow to reddish brown. Thirty six shades with appreciable change in hue and tone were obtained by varying mordants combinations as well as dye concentrations and investigated for colour characteristics and fastness properties. The use of mixed mordants produces significant improvement in depth of shade with remarkable changes in colour parameters. Dyed woollen yarns, in general, showed acceptable fastness to light, washing and rubbing. No considerable difference in light and wash fastness values were observed between mordanted and un-mordanted samples, however rub fastness values were improved significantly after mordanting

Mixed metal mordant dyeing of wool using root extract of Rheum emodi (Indian Rhubarb/Dolu)

In the present study, the root extract of Rheum emodi (Indian Rhubarb/Dolu/Revandchini) has been used as a natural dye to develop a variety of harmonizing natural shades on woolen yarn using combination of ecofriendly mixed metal mordants. Dyeings were carried out in neutral acidic, and alkaline medium using 0.5%–5% dye concentrations pre-treated with (4.5% iron + 0.1% tin), (2.5% iron + 0.5% tin), and (0.5% iron + 0.9% tin) mordant combinations. A total of 54 shades have been developed by varying the amount of dye and percentage combination of mordants. The hue of color ranged from reddish-brown, greenish-yellow to dark yellow. The color of dyed woolen yarns was investigated in terms of color strength (K/S), CIELab, CIELch values. Fastness properties (light, washing, and rub/crocking) of dyed woolen yarn samples were also assessed

SALVAGE SURGERY FOR ANAL CANAL CA. LONG TERM OUTCOMES FROM A TERTIARY REFERRAL CENTRE

Purpose: The purpose of this study was to analyse the outcome of salvage surgery in the management of anal canal cancer.Methodology: All patients with a diagnosis of anal canal carcinoma from 2006 to 2015 were studied. Basic demographic data were recorded. Treatment modalities used were recorded for all patients. Long-term surgical outcomes were recorded. Median survival in months was recorded. All data were recorded in the SPSS ver. 20.Results: A total of 62 patients were included in the study. Median age was 51. 38 patients had SCCa on histology and 24 had an adenocarcinoma. 52% of patients had a T4 lesion. Chemoradiotherapy (CRT) was offered to 59 (95%) patients as the first line of therapy. 12 (19%) patients had a complete response. 37 (60%) patients had a partial and 10 (16%) patients had no response to chemoradiation. Salvage surgery was offered to 27 patients. Of these, 21 had a curative resection. Six had irresectable disease and underwent a colostomy only. Median overall survival for all patients was 46 months with a 5-year survival of 55%. Patients with partial response who were offered salvage surgery the 5-year survival were 40%. For patients with no response or progressive disease after chemoradiation therapy, the 5-year survival was 20%.Conclusion: Long-term survival can be achieved in majority of patients who undergo radical salvage surgery after failed CRT for carcinoma of the anal canal.Key words: Adenocarcinoma, anal canal, chemoradiotherapy, surger