Continuous and scalable manufacture of amphibious energy yarns and textiles

Abstract

Biomechanical energy harvesting textiles based on nanogenerators that convert mechanical energy into electricity have broad application prospects in next-generation wearable electronic devices. However, the difficult-to-weave structure, limited flexibility and stretchability, small device size and poor weatherability of conventional nanogenerator-based devices have largely hindered their real-world application. Here, we report a highly stretchable triboelectric yarn that involves unique structure design based on intrinsically elastic silicone rubber tubes and extrinsically elastic built-in stainless steel yarns. By using a modified melt-spinning method, we realize scalable-manufacture of the self-powered yarn. A hundred-meter-length triboelectric yarn is demonstrated, but not limited to this size. The triboelectric yarn shows a large working strain (200%) and promising output. Moreover, it has superior performance in liquid, therefore showing all-weather durability. We also show that the development of this energy yarn facilitates the manufacturing of large-area self-powered textiles and provide an attractive direction for the study of amphibious wearable technologies.

Fig. 1

Continuous manufacture of amphibious energy yarns. a Schematic diagram of a specialized melt-spinning process for scalable manufacture of single-electrode triboelectric yarn (SETEY). Light pink indicates silicone rubber tube while purple indicates stainless steel yarn. F_x1 and F_x2 are the tensile force on the silicone rubber tube during the stress storing and releasing, respectively. F_y is the resultant gravity. The rotational speed (V₁) of compaction roller I equals to that (V₂) of compaction roller II. The rotational speed (V₃) of reeling roller = r₂V₂/(1 + ε)r_3, where r₂ and r₃ are radius of the compaction roller II and reeling roller, respectively. ε is prestrain. Insets (1) and (2) are enlarged cross-sectional views of compaction rollers I and II, respectively. b The enlarged view of silicone rubber tube molding process. Temperature: 250–280 °C in area I, 120–180 °C in area II, and 30–50 °C in area III. c The photograph of SETEY collected on reeling rollers. Inset: the enlarged view of an individual SETEY

Fig. 2

Working mechanism of the single-electrode triboelectric yarn. a Kinetic demonstration of the stretching process of the SETEY. b A potential well model proposed for explaining charge transfer during the contact and separation of two materials under a single electrode. D is the distance between potential wells of inner stainless steel yarn and silicone rubber tube sheath, E_S and E_R are the occupied energy levels of electrons in the atoms of stainless steel yarn and silicone rubber tube, E₁ and E₂ are the required potential energies for electrons to escape from the surfaces of stainless steel yarn and silicone rubber tube, respectively. E_S and E_R are respectively smaller than E₁ and E₂. c Simulation results of the potential distribution of the SETEY by using COMSOL software. From left to right: the potential on the silicone tube gradually increases and the potential on the stainless steel yarn remains stable. SETEY single-electrode triboelectric yarn

Fig. 3

Working mechanism of amphibious energy yarns during underwater operation. a The output voltages of the single-electrode triboelectric yarn (SETEY) in nitrogen, cyclohexane, methylbenzene, diethyl ether, ethyl acetate, phenylcarbinol, alcohol and water. A SETEY with sheath thickness of 0.5 mm and length of 30 cm was tested in these experiments. The error bars correspond to standard deviation caused by the statistical uncertainty of measurement. b The output voltages of SETEYs with different sheath thickness measured in nitrogen and water. The principle of field intensity superposition $\left(\overrightarrow{\mathbf{E}}=\sum _n\overrightarrow{{\mathbf{E}}_{\mathbf{n}}}=\frac{1}{4\mathrm{\pi }{K}_{\mathrm{s}}}\sum _n\frac{q_n}{r_n^2}\overrightarrow{{\mathbf{r}}_{\mathbf{n}}}\right)$ is used to describe the relationship between the electric field intensity at different locations and its distance to the point charge group.$\overrightarrow{{\mathbf{E}}_{\mathbf{n}}}$ is the electric field intensity of a point charge at a certain point, which is a vector. q_n is the charge of a point charge. $\overrightarrow{{\mathbf{r}}_{\mathbf{n}}}$ is the radial vector from a certain point in the electric field to a point charge. K_s is the relative dielectric constant of the silicone rubber. $\overrightarrow{\mathbf{E}}$ is the total electric field intensity at a certain point under the point charge group. The error bars correspond to standard deviation caused by the statistical uncertainty of measurement. c Schematic of a dynamic polarization process during single cyclic tensile of the SETEY in water. Water exhibits distinct layered structures near surface of the silicone rubber tube. h_i and h_s are the thicknesses of the interfacial water and the silicone rubber wall, respectively. K_i and K_b are dielectric constants of the interfacial water and the bulk water, respectively. K_i is only ~2 ^, while h_i is only 1.5−2 nm; therefore, interfacial water is difficult to reorient in electric field^–. The surface potential from triboelectrification only interacts with bulk water (K_b ≈ 80). d Digital photos showing the self-powered application: A liquid crystal display (LCD) is lit up by the SETEY in water. e The output performances of the SETEY measured under different depth in water

Fig. 4

Structure design and electrical output performance of the energy textiles. a Fabrication processes of the e-textile. b Resultant torsional moment diagram of the double-plied yarn. M₁ and M₂ are the torsional moments of the two primary plied yarn, respectively. M₃ is the torsional moment of the double-plied yarn. Their resultant torsional moment is 0, namely M₃ = M₁ + M₂. c Photographs of the experiment setup with a stretch-retraction mode. d Electrical outputs of four distinct patterns measured under 100% tensile strain at a fixed frequency of 0.5 Hz. e Output voltage of the warp-weft-connection single-electrode e-textile measured at different frequency (0.5–5 Hz) with a 100% tensile strain. The error bars correspond to standard deviation caused by the measurement noise. f Output performance of the warp-weft-connection single-electrode e-textile measured under different tensile strain (25, 50, 75 and 100%). The error bars correspond to standard deviation caused by the statistical uncertainty of measurement. g Output current/voltage, and h power of the warp-weft-connection single-electrode e-textile measured at different external load resistances varied from 50 KΩ to 1 GΩ with a fixed frequency of 0.5 Hz. i An image of a self-charging system that harvests biomechanical energy by the e-textile to power an electronic watch. j A snapshot of an e-textile working underwater. k The electrical output results of the e-textile after repeated washing