Highly Conductive and Flexible Nylon-6 Nonwoven Fiber Mats Formed using Tungsten Atomic Layer Deposition

Abstract

Low-temperature vapor-phase tungsten atomic layer deposition (ALD) using WF6 and dilute silane (SiH4, 2% in Ar) can yield highly conductive coatings on nylon-6 microfiber mats, producing flexible and supple nonwovens with conductivity of ∼1000 S/cm. We find that an alumina nucleation layer, reactant exposure, and deposition temperature all influence the rate of W mass uptake on 3D fibers, and film growth rate is calibrated using high surface area anodic aluminum oxide. Transmission electron microscopy (TEM) reveals highly conformal tungsten coatings on nylon fibers with complex "winged" cross-section. Using reactant gas "hold" sequences during the ALD process, we conclude that reactant species can transport readily to reactive sites throughout the fiber mat, consistent with conformal uniform coverage observed by TEM. The conductivity of 1000 S/cm for the W-coated nylon is much larger than found in other conductive nonwovens. We also find that the nylon mats maintain 90% of their conductivity after being flexed around cylinders with radii as small as 0.3 cm. Metal ALD coatings on nonwovens make possible the solvent-free functionalization of textiles for electronic applications.

Conductivity and touch-sensor application for atomic layer deposition ZnO and Al:ZnO on nylon nonwoven fiber mats

“…1,4 Zinc oxide is easily deposited by atomic layer deposition (ALD) at low temperatures (<200 C) using diethyl zinc (DEZ) and water, [1][2][3][4][5] and adding cycles of trimethylaluminum (TMA), trimethylgallium, or trimethylindium to the ALD sequence leads to Al-doped ZnO (AZO), 1,4 Ga-doped ZnO, 4,6 or In-doped ZnO, 6,7 respectively. 8 Nylon-6 is an attractive example nonwoven substrate, in part, because it does not begin to melt until $215 C. 9 Previous reports demonstrate ZnO ALD on various polymer fiber substrates including nylon-6, 10-12 cotton, 13 paper, 13 polypropylene, 5,12-14 polyethylene terephthalate, 14 polybutylene terephthalate, 15 polylactic acid, 16 and polyacrylonitrile. 3 For conductive coatings on polymer fibers, nonwoven fiber mats are highly versatile because they can be produced in high volume at low cost, in many polymer chemistries, and offer control over fiber geometry, fiber diameter (10 lm to <100 nm), web density, and specific surface area.…”

Atomic layer deposition onto carbon fiber fabrics

“…26,27 Especially ALD onto textiles made from polymeric fibers like cotton, 28-31 cellulose 32,33 ,polyester, 30,34 polyamide, 35,36 polypropylene 36,37 , and silk 38,39 was successfully demonstrated in the literature. 26,27 Especially ALD onto textiles made from polymeric fibers like cotton, 28-31 cellulose 32,33 ,polyester, 30,34 polyamide, 35,36 polypropylene 36,37 , and silk 38,39 was successfully demonstrated in the literature.…”

“…26,27 Especially ALD onto textiles made from polymeric fibers like cotton, 28-31 cellulose 32,33 ,polyester, 30,34 polyamide, 35,36 polypropylene 36,37 , and silk 38,39 was successfully demonstrated in the literature. 35 These investigations focused primarily on organic fabrics. 28,29,39 Furthermore, conductive ALD metal coatings on polymer fabric can enable flexible and wearable electronics.…”

“…Although ALD originates from semiconductor technology, nowadays it finds increasing interest in other areas, for example for the coating of fibrous and textile materials. 26,27 Especially ALD onto textiles made from polymeric fibers like cotton, 28-31 cellulose 32,33 ,polyester, 30,34 polyamide, 35,36 polypropylene 36,37 , and silk 38,39 was successfully demonstrated in the literature. Inorganic coatings on such fibers can for example lead to a higher water contact angle and can protect these fabrics from collecting dirt.…”

“…28,29,39 Furthermore, conductive ALD metal coatings on polymer fabric can enable flexible and wearable electronics. 35 These investigations focused primarily on organic fabrics. There is a smaller number of papers on ALD coating of inorganic fabrics.…”