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Functional Nanostructured Materials (including low-D carbon)
Screen Printing of Graphene Oxide Patterns onto Viscose Nonwovens with Tunable Penetration Depth and Electrical Conductivity Jiangang Qu, Nanfei He, Shradha V Patil, Yanan Wang, Debjyoti Banerjee, and Wei Gao ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b00715 • Publication Date (Web): 28 Mar 2019 Downloaded from http://pubs.acs.org on March 28, 2019
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ACS Applied Materials & Interfaces
Screen Printing of Graphene Oxide Patterns onto Viscose Nonwovens with Tunable Penetration Depth and Electrical Conductivity Jiangang Qua,b, Nanfei Heb, Shradha V. Patilb, Yanan Wangb, Debjyoti Banerjeeb, Wei Gaob* a School b
of Textile and Clothing, Nantong University, Nantong, Jiangsu 226019, China
Textile Engineering, Chemistry, and Science Department, North Carolina State University,
Raleigh, NC 27606, USA
ABSTRACT. Graphene-based e-textiles have attracted great interests due to their promising applications in sensing, protection, and wearable electronics. Here we report a scalable screen-printing process along with continuous pad-dry-cure treatment for the creation of durable graphene oxide (GO) patterns onto viscose nonwoven fabrics at controllable penetration depth. All the printed nonwovens show lower sheet resistances (1.2-6.8 kΩ/sq) at a comparable loading as those reported in literature, and good washfastness, which is attributed to the chemical crosslinking applied between reduced GO (rGO) flakes and viscose fibers. This is the first demonstration of tunable penetration depth of GO in textile matrices, wherein GO is also simultaneously converted to rGO and cross-linked with viscose fibers in our processes. We have further demonstrated the potential applications of these nonwoven fabrics as physical sensors for compression and bending. KEYWORDS. graphene oxide, screen printing, crosslinking, e-textile, textile sensors
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E-textiles, with capabilities of physiological sensing, wireless communication, energy harvesting and storage etc., have received enormous attention recently due to their potential applications in military uniforms, healthcare medical textiles, high-performance sportswear, and even fashion-show garments.1-6 However, the conductive materials involved so far, including high-cost metals,7 carbon nanotubes,8 transition metal oxides,9 conductive polymers,10 are not only uneconomic, but also toxic and nonbiodegradable.11 Graphene oxide (GO) and its derivatives directly derived from natural/synthetic graphite are reasonable alternatives for relevant applications which have been extensively studied for sensing, separation, conduction, and energy-storage applications over the last decades, mainly due to their extraordinary molecular-level properties such as excellent electrical and thermal transport, high surface area, aqueous dispersibility/processability and good mechanical properties.12-16 However, its scalable and tunable integration into textile systems for intended applications is currently only in its infancy.1 Various strategies have been employed for the preparation of graphene-based textiles, such as dip coating,17 electrostatic self-assembly,18 inkjet printing,19,20 chemical vapor deposition,21 brush coating22 and vacuum filtration.23 Although these processing methods work in small scale, the associated high costs and the limited processing dimension hinders their applications in large-scale.1 In traditional textile industry, screen printing and pad-dry-cure processes are considered the most efficient, low cost and large-scale production technologies to textile dyeing and finishing. Both processes have also been used to integrate electronic devices directly onto textile substrates.4,
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The pad-dry-cure process is effective in dyeing textiles with a uniform 2
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color, while the screen printing process can yield colored patterns in an efficient manner,25 sometimes with tunable penetration of the dyestuff involved.26 Tunable penetration depth on textile substrates is especially favorable for e-textile systems, since more human comfort and biosafety can be explored through limited or eliminated intimate contact of active components with human skin. Moreover, screen printing process ensures the pattern to be repeatedly positioned at the same location over the human body,27 leading to improved accuracy of sensing and effective utilization of active materials. Although stratagem of screen printing of GO on cotton was reported,28 the thickening agent could be redundant, and significance of tunable penetration depth needs to be developed. For wet processing, GO and its derivatives are generally chosen over intact graphene systems because of their scalability and wet-chemical processability and reactivity. Negative charges on GO can assist in its formation of a stable dispersion in water and allow for its interaction with hydroxyl groups on cellulose fibers/fabric surfaces.13 The effective interactions and strong bonding between GO and fiber substrate is crucial for the full utilization of GO derivatives in smart textiles. Unfortunately, so far, limited investigations have been performed on the crosslinking between GO and cellulosic fibers. There have been a few reports on the modification of cotton surfaces, either by plasma treatment29 or cationizing,30 where the use of toxic chemical such as hydrazine hydrate as a reducing agent poses challenges on scalability. Benign reagents such as Vitamin C31,32 and L-cysteine33 have also been used to generate reduced GO (rGO) but are generally considered less effective and time-consuming. Therefore, it is highly desirable to identify an effective and non-toxic crosslinking-reduction recipe for the scalable 3
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production of GO/rGO-based e-textiles.
Figure 1. Schematic diagram of the fabrication process of our viscose nonwoven fabric-based sensors, with tunable penetration depth of GO. Herein, we report a lab-scale screen-printing process to create GO patterns onto viscose nonwovens with controlled penetration depth that can be readily scaled up to industrial production. In our procedure, GO was chemically reduced and cross-linked with cellulosic fabric simultaneously with butane tetracarboxylic acid (BTCA) and sodium hypophosphite (SHP), reagents that are commercially available and commonly used for textile formaldehyde-free durable finishing study.34,35 As illustrated in Figure 1, a GO/H2O dispersion is prepared and used as the printing paste. A modified drawdown coater is used as screen printing setup, by which patterns and tunable penetration depth of GO on fabric can be obtained. The lab-scale printing process has been recorded as shown in Supplementary video 1. The GO printed and cross-linked fabric (GPC-F) is subsequently prepared, as GO is reduced and cross-linked with the fabric via a 4
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continuous pad-dry-cure unit that has been widely adopted in textile industry for dyeing and finishing. The correlation between the penetration depth and the GO dispersion concentration has been clarified, while the electrical behaviors of the resulted rGO patterns have been characterized as a function of penetration depth, chemical crosslinking, compression, and bending. RESULTS AND DISCUSSION Figure 2a depicts a SEM (Scanning Electron Microscopy) image of GO sheets synthesized by a modified Hummers method.36 Visible wrinkles and sharp edges can be seen in each GO sheet. The lateral dimensions of GO sheets prepared show a relatively wide range from 0.8 μm to 28.9 μm, and the average size is ca. 4.5 μm (distribution of lateral dimensions is shown in Figure S1, supporting information). Apart from GO sheet sizes, the rheology of GO dispersions are the key factors to consider when developing screen printable GO paste.37 As shown in Figure 2b, the apparent viscosity of GO dispersion increase dramatically with the increase in the concentration at relatively low shear rates (
