Achieving Highly Conductive, Stretchable, and Washable Fabric from Reactive Silver Ink and Increased Interfacial Adhesion

Abstract

There is a major need to manufacture highly electrically conductive fabrics with stretch- and wash-durability. In this work, we provide both modeling and experiments of the mechanical failure of silver ink coatings on knitted fabric. Large thickness metal films are needed for high conductance but tend to debond from the underlying fabric microfibers that lead to cracking and failure. Strong adhesion between the metal film and microfiber is thus key to achieving high thickness films with good mechanical robustness. The use of a reactive silver ink addresses this need due to in situ silver reduction and conformal coverage. Furthermore, a chemical etchant pretreatment of the textile microfibers functionalizes the surface to enable covalent bonding with the surface and increases theinterface area. The use of a polymer provides for an additional protective barrier during washing. Treated fabrics demonstrate low sheet resistance <100 mΩ per square with only two coats and <200 mΩ per square after 1000 stretching cycles or 300 min of ultrasonic washing with detergent.

Ink-Coated Silver Films on PET for Flexible, High Performance Electromagnetic Interference Shielding and Joule Heating

“…The silver ink consists of a reactive silver ink, which can achieve high conductivities at low curing temperatures. 35 Coated samples with a thickness of 11.7 μm were observed to have sheet resistance as low as 56.9 mohm/sq and SE as high as 82.6 dB EMI in the X band (8−12 GHz) and 85.3 dB EMI in the Ku band (12)(13)(14)(15)(16)(17)(18). Without the PUD, the silver films crack after a single bend.…”

“…Traditional EMI shielding consists of metal cages, foils, and meshes. − However, these materials are thick, heavy, bulky, and rigid and are unsuitable for flexible electronics and wearables . Conventional EMI shielding is fabricated by subtractive manufacturing methods such as die cutting, extrusion, or molding, which consume much material and energy and their cost is high. , New lightweight EMI shielding materials are needed that may accommodate a variety of substrates including polyethylene terephthalate (PET) for flexible electronics or textiles for wearable electronics. , …”

“…However, there are some shortcomings with these methodsthey usually require vacuum or high energy to perform the deposition. Recent research in conductive inks ,, and additive manufacturing methods such as gravure, flexographic, offset, and inkjet printing have demonstrated the ability to print electronics on a variety of soft and flexible substrates, while reducing material and energy consumed. , These 3D printing technologies provide high throughput, lightweight, and roll-to-roll process integration …”

“…12,13 New lightweight EMI shielding materials are needed that may accommodate a variety of substrates including polyethylene terephthalate (PET) for flexible electronics 14 or textiles for wearable electronics. 15,16 It is important to achieve high SE with small thicknesses, as larger thickness films tend to more easily debond, crack, and tear during bending. 15 The bending stiffness of a film is proportional to the cube of its thickness 17 and thus, thinner materials are more desirable for flexible electronics.…”

“…15,16 It is important to achieve high SE with small thicknesses, as larger thickness films tend to more easily debond, crack, and tear during bending. 15 The bending stiffness of a film is proportional to the cube of its thickness 17 and thus, thinner materials are more desirable for flexible electronics. 18 For military defense applications, the requirement for SE is higher than 80 dB.…”