Advances in Functional Finishing of Textiles PDF by Mohammad Shahid and Ravindra Adivarekar

Contents

Surface Modification of Textiles with Nanomaterials for Flexible Electronics Applications

Abstract 

In the recent past, wearable electronics has emerged as one of the significant products of nanoscience and nanotechnology initiatives. Multi-functional textiles achieved by means of surface modification with nanomaterials are a promising strategy by which flexible and wearable electronics, also called as “next generation electronics” could be developed. Nanostructured metal and metal oxide materials, metal organic frameworks (MOF), nanostructured carbon derivatives and conducting polymers are themajor kinds of materials being used to modify the surface of textiles for the fabrication of wearable devices. In this chapter, modification or functionalization of textile surface with nanomaterials through predominantly used techniques like Physical Vapour Deposition (PVD), Chemical Vapour Deposition (CVD) and other chemical techniques have been reviewed. Also, applications of wearable textiles with functionalized surface for energy harvesting, electromagnetic interference filter with special focus on UV, and wearable sensors for healthcare and environment quality monitoring, etc., have been highlighted.

Keywords Multifunctional textiles ・ Surface modification techniques ・ Metal organic frameworks ・ Nanomaterials ・ Flexible electronics ・ Wearable sensors

1 Introduction
Nanomaterials are highly functional as well as versatile and can be utilized for a variety of applications. Nanomaterials are like alchemists; different combinations of chemical precursors and physical conditions can result in versatile nanostructures that finds utility in a range of applications [1]. In recent years, materials scientists have taken a paradigm shift and concentrated on engineering nanomaterials, where they intentionally design and develop synthetic materials with the desired physiochemical properties for a targeted purpose or function [2]. Nanomaterials have greatly enhanced the functional properties of matter, making them the most sought-after candidate for biocompatible applications like drug delivery [3], nanosensors [4] and nanomaterial modified textiles [5].

The demand for highly durable and functional garments has resulted in a growing necessity for textiles modified with nanomaterials. Nanomaterials offer enhanced functionalities to textiles such as enhancement of oil/water repellence [6], ultraviolet (UV) blocking ability [7], reduction ofwrinkles [8], elimination of static charge build up [9], continuous monitoring of bodily functions and metabolism [10], rehabilitation, toxicity reduction [11], long term durability, and environmental impact without compromising their flexibility or comfort. This new approach has opened up several windows in the wearable and flexible technologies including garments, which is capable of sensing and responding to environmental stimuli including mechanical, chemical, electrical, thermal, optical, or magnetic sources. Studies have been conducted on electronic and photonic nanomaterials [12] integrated with textiles especially, to validate their plausible potential in sensing, optical displays [13], and drug delivery applications where they are examined in terms of their performance, durability, and connectivity.

Cotton is widely preferred by textile manufacturers towards realizing wearable textiles owing to its high absorbing capacity, chemically adaptable surface and flexibility. Notwithstanding these merits, the fibres of cotton fabrics have lower strength and easily flammable nature. As a result, such exacerbating properties of natural cotton imparts greater limitations in (i) electronic applications (where repeatability and durability at end user); (ii) antibacterial actions of cotton relatively decreases as a consequence of laundering [14]. To overcome these challenges with cotton, synthetic fibres have emerged as the other alternatives. It has been proved to have better anti-microbial and stain-resistance properties but at the cost of comfort. Thus, nanoengineered fabrics would plausibly stand as a conglomeration of the merits of both natural and synthetic fibres, while furnishing novel functionalities.

Chemical vapour deposition (CVD) and physical vapour deposition (PVD) techniques offer several advantages for surface modification of textiles [15]. Among the two techniques, PVD has proven to furnish high adherent coatings. PVD is a thin film coating technique, which involves condensation of vaporized thin film materials over the substrate/textile. PVD is generally conducted in vacuum, thereby offering high purity and uniformly coated thin films owing to the increased mean free path of the sputtered atoms. PVD techniques include cathode arc deposition, pulsed laser deposition, electron beam evaporation, evaporative deposition, sputtering, ion plating, thermal evaporation, and enhanced sputtering. The general mechanism in PVD techniques involve evaporation of the solid thin film materials to be coated onto the substrate by heat or ion bombardment (sputtering) [16]. Simultaneously, a reactive species in the form of gas is introduced into the vacuum chamber to form a compound with the target and the reactive species, which is subsequently coated on the surface of the substrate/textile as a thin film. Such deposited thin films are generally used in applications that demands high purity and repeatability in its functionality.

On the other hand, thin films preparation through CVD techniques like spray coating, dip coating were carried out at atmospheric environment, where the influence of other gases in the atmosphere might influence and modify the prepared samples. These modifications limit the potential applications of the prepared samples. However, preparation of high purity thin films using PVD techniques fulfil the required demands and hence could be potentially employed in many applications like aircraft parts, biomedical instrumentations, optical devices, surface modification of textiles, etc.

Textile has proven to be a versatile substrate for the integration of nanostructured materials owing to its universality and the same has been exploited for the fabrication of wearable electronics devices. Laundering greatly decreases the effects imparted by functionalization of the fabrics thereby reducing its long-term usage. This poses a significant challenge in developing functional textiles. Hence, nanotechnology plays a major role in introducing unique and permanent functional fabrics.