Cotton Fabrics Decorated with Conductive Graphene Nanosheet Inks for Flexible Wearable Heaters and Strain Sensors

Abstract

Wearable conductive fabrics are an essential part of flexible electronics, which can be used as portable devices for human thermal management, healthcare, and motion detection. However, obtaining low-cost and scalable production of these types of conductive fabrics with high conductivity, low-voltage-activating electrothermal response, and satisfactory washability still has critical challenges. Herein, high-conductive graphene ink-decorated cotton fabrics (CFs) are fabricated via a facial double-side screen-printing technique for flexible wearable heaters and strain sensors. The porous and rough CFs with spatially distributed graphene inks create efficient pathways for electron movement, and the outmost water-soluble polyurethane could dramatically promote the washability, cycling stability, and environmental resistance properties of conductive fabrics. Interestingly, the as-obtained graphene conductive textiles demonstrate high conductivity (1.18 × 104 S/m), which are applied to flexible wearable heaters, showcasing a high steady-state temperature (52.6 °C) at a low voltage of 3 V, excellent washability, cycling stability, and environmental resistance properties. Additionally, the fabricated conductive fabrics can also be applied to wearable strain sensors, which exhibit high sensitivity, excellent recovery, and stability in a refined strain range for responding to human motions. Consequently, the designed graphene conductive fabrics provide a promising strategy to realize low-cost and scalable next-generation wearable electronic textiles.

Advances in the Robustness of Wearable Electronic Textiles: Strategies, Stability, Washability and Perspective

“…The wearable heater made of graphene-ink printed cotton fabric sustained 10 washing cycles in 0.1 wt.% detergent aqueous solution at different temperatures. The effect of the washing temperature on the heating performance of the device was found to be very minimal (1.38% and 1.46% variations in the heating temperature profile observed for washing at 20 • C and 50 • C, respectively) (Figure 10k) [270].…”

Printed Stretchable Graphene Conductors for Wearable Technology

“… 8 Recently, printed stretchable sweat sensors were realized from an ink containing GNP and a thermoplastic polyurethane (TPU) binder in N -methyl-2-pyrrolidone (NMP), 33 and strain sensors were produced by decorating cotton fabrics with a GNP-based ink followed by a polyurethane layer. 42 Although these inks offer significant progress, additional strategies are needed to realize graphene-based inks with adjustable rheology, to increase the conductivity of printed tracks, and to preserve stretchability over many cycles.…”

“…GNP-based inks suitable for screen printing of flexible conductors with applications in sensors, photovoltaics, and wireless communications have already been demonstrated. − Beyond flexibility, many applications require stretchability. ,,, The main difference between flexible and stretchable printed electronics is the strain level reached in each case, which is orders of magnitude higher in stretchable electronics. This is essential for applications such as athletic garments, on-body sensors, , sensory artificial skin, wearable energy storage devices, stretchable light-emitting diodes (LEDs), soft robotics, , strain sensors, − and cardiac implants . Furthermore, stretchability is expected to generally improve the lifetime of flexible electronic devices by reducing fatigue and enables conformal printing to nonflat, flexible substrates …”

“…Lately, graphene-based strain sensors have been manufactured through screen printing. − In addition, stretchable supercapacitors were printed from inks composed of a conductive polymeric binder (PEDOT:PSS) to which some graphene was added to enhance the performance . Recently, printed stretchable sweat sensors were realized from an ink containing GNP and a thermoplastic polyurethane (TPU) binder in N -methyl-2-pyrrolidone (NMP), and strain sensors were produced by decorating cotton fabrics with a GNP-based ink followed by a polyurethane layer . Although these inks offer significant progress, additional strategies are needed to realize graphene-based inks with adjustable rheology, to increase the conductivity of printed tracks, and to preserve stretchability over many cycles.…”

Synthesis and Application of Tackifying Dispersant Poly (Vinyl Alcohol-Acrylic Acid-Triallyl Cyanate)

“…Meanwhile, researchers are rarely involved in the application of modified thickeners [ 17 ]. For example, applications in wearable and implantable conductive textile materials have increased in recent years [ 18 , 19 , 20 ], one method of which is preparing the graphene (Gr) finished onto the surface of the fabric via multiple impregnation [ 20 , 21 ]. However, the surface of Gr lacks groups that form a good combination with textile materials, showing the poor adhesion between Gr and the matrix, along with weak physical fastness, seriously affecting the product quality [ 22 ].…”