Machine embroidery of light-emitting textiles with multicolor electroluminescent threads

Abstract

Advances in electroluminescent threads, suitable for weaving or knitting, have opened doors for the development of light-emitting textiles, driving growth in the market for flexible and wearable displays. Although direct embroidery of these textiles with custom designs and patterns could offer substantial benefits, the rigorous demands of machine embroidery challenge the integrity of these threads. Here, we present embroiderable multicolor electroluminescent threads-in blue, green, and yellow-that are compatible with standard embroidery machines. These threads can be used to stitch decorative designs onto various consumer fabrics without compromising their wear resistance or light-emitting capabilities. Demonstrations include illuminating specific messages or designs on consumer products and delivering emergency alerts on helmet liners for physical hazards. Our research delivers a comprehensive toolkit for integrating light-emitting textiles into trendy, customized crafts tailored to the unique requirements of diverse flexible and wearable displays.

Fig. 1.. Embroiderable multicolor EL threads.

(A) Schematic illustration of producing the EL threads and their subsequent use in machine embroidery for crafting light-emitting textiles. (B) Schematic representation of a light-emitting pixel formed at the contact point between the EL thread and transparent conductive fiber (TCF). (C) Photographs of the multicolor light-emitting pixel arrays. (D) Photographs showcasing the light-emitting textiles embroidered on a cotton towel, flag, t-shirt, and rug.

Fig. 2.. Physical and optical characterizations of EL threads.

(A) Shear rate dependence of the viscosity of ZnS phosphor/TPU slurries. (B) Weight ratio dependence of thread diameter with respect to ZnS phosphors and TPU. Error bars represent SD, n = 3 for each group. (C) Load-strain curves comparison of a plain thread and the EL threads with different weight ratios of ZnS phosphors and TPU. (D) Surface roughness comparison of a plain thread and the EL threads with different weight ratios of ZnS phosphors and TPU. (E) Weight ratio dependence of EL intensity of the EL threads with respect to ZnS phosphors and TPU. Error bars represent SD, n = 3 for each group. (F) Luminance distribution around the circumference of the EL threads. Error bars represent SD, n = 3 for each group. a.u., arbitrary units.

Fig. 3.. Overall structure and characterization of light-emitting pixels.

(A) Schematic representation, side-view, and top-view photographs of a light-emitting pixel created at the point of contact between the EL thread and TCF. (B) Photographs of the light-emitting pixels at various stitch distances and angles. (C) Relative EL intensity of the light-emitting pixels in relation to the stitch distance and angle between the EL thread and TCF. Error bars represent SD, n = 3 for each group. (D) Relative EL intensity of the light-emitting pixels as a function of upper thread tension. Error bars represent SD, n = 3 for each group. (E) Relative EL intensity of the light-emitting pixels under repetitive pressing and releasing cycles.

Fig. 4.. Light emission characteristics.

(A) Luminance variation of the light-emitting pixels in response to applied voltages at different frequencies (circles) and corresponding fitting curves (lines). (B) Current density of the light-emitting pixels with respect to applied voltages at different frequencies. (C) Power consumption of the light-emitting pixels with respect to luminance at different frequencies. (D) Photographs of light-emitting textiles under stretching, bending, and rolling. (E) Relative EL intensity of the light-emitting pixels during 10,000 stretching cycles at a tensile strain of 20%. Error bars represent SD, n = 3 for each group. (F) Relative EL intensity of the light-emitting pixels during 10,000 cycles of vertical, diagonal, and horizontal folding. Error bars represent SD, n = 3 for each group. (G) Relative EL intensity of the light-emitting pixels during multiple laundry cycles. Insets show photographs of the corresponding light-emitting textile. Error bars represent SD, n = 3 for each group. (H) Local temperature variations of the light-emitting pixels. Error bars represent SD, n = 3 for each group. (I) Thermal images of the light-emitting pixels after continuous operation up to 6 hours.

Fig. 5.. Proof-of-concept demonstrations.

(A) Schematic representation of the comprehensive head impact monitoring system, which incorporates a 6 × 3 array of light-emitting pixels into a commercial helmet liner designed for compatibility with a football helmet and includes an integrated impact sensor. (B) Photographs of the illuminated light-emitting pixels following an impact in either the x direction (θ = 0°) or at an oblique angle (θ = 70°) with varying levels of impact severity (mild, moderate, and severe).