Ultraelastic Yarns from Curcumin-Assisted ELD toward Wearable Human-Machine Interface Textiles

Abstract

Intelligent human-machine interfaces (HMIs) integrated wearable electronics are essential to promote the Internet of Things (IoT). Herein, a curcumin-assisted electroless deposition technology is developed for the first time to achieve stretchable strain sensing yarns (SSSYs) with high conductivity (0.2 Ω cm^-1) and ultralight weight (1.5 mg cm^-1). The isotropically deposited structural yarns can bear high uniaxial elongation (>>1100%) and still retain low resistivity after 5000 continuous stretching-releasing cycles under 50% strain. Apart from the high flexibility enabled by helical loaded structure, a precise strain sensing function can be facilitated under external forces with metal-coated conductive layers. Based on the mechanics analysis, the strain sensing responses are scaled with the dependences on structural variables and show good agreements with the experimental results. The application of interfacial enhanced yarns as wearable logic HMIs to remotely control the robotic hand and manipulate the color switching of light on the basis of gesture recognition is demonstrated. It is hoped that the SSSYs strategy can shed an extra light in future HMIs development and incoming IoT and artificial intelligence technologies.

Keywords: curcumin; electroless deposition; human–machine interfaces; textiles; wearable electronics.

Figure 1

The illustration of fabrication process of SSSYs and observations of elastic yarns in each different state (bottom).

Figure 2

a) The transmittance FTIR spectrum of the raw elastic yarn (black) and the curcumin‐coated core‐spun yarn (red). b) The XPS spectrum of Pd 3d for the Pd/curcumin sample. c) The XRD spectrum of Ni‐coated samples (black) and Cu‐coated yarns (red). d–i) SEM images of the pristine yarn, the copper‐coated yarn (30 min ELD), Ni coatings (60 min ELD) at 2.5 keV, the pristine yarn in high magnification, the copper‐coated yarn in high magnification (the inset is the magnified image), and Cu coatings (60 min ELD) at the low‐voltage mode, respectively.

Figure 3

a) The conductivity results of Ni (black) or Cu (red)‐coated yarns at different ELD durations (n = 5). SEM images and the scheme illustrations of nickel‐coated yarns at b) 0% strain and c) 50% strain. d) The resistance changes of conductive yarns when stretching and releasing at different strains. e) The resistance changes of as‐made nickel‐based yarns when continuously stretching to 300% elongation (n = 5). f) Resistance stability of sensor materials under repetitive stretching (50% strain) and relaxing (0% strain) cycles (the change in resistance is defined as: R/R ₀) (n = 5). g) The tensile test of raw elastic yarns and Ni‐coated stretchable yarns (the original sample length is 45 mm). The durability test of Cu‐coated samples including h) air stability (n = 5) and i) washing fastness (n = 5).

Figure 4

Deformation mechanics analysis of the metal‐coated core‐spun yarns: structural illustrations with a) side view without deformation, b) cross‐sectional view without deformation, and c) detached nylon windings under tension. d) The comparison of theoretical prediction with experimental results for SSSY under tension (n = 3). e) Simplified beam model for the deformation of SSSY attached in smart glove system (a straight beam when relaxing and a deformed beam when bending), ρ is the radius of the deformed beam. f) The comparison of analytical prediction with experimental values for bending angle–resistance responses of Ni‐coated core‐spun yarns (n = 3).

Figure 5

a) Schematic diagram of the human–machine remote control system. b) The resistance values of five fingers under different strains. Applications c) to control the robotic hand and d) to control the color of light by using hand gestures.