Highly conductive, stretchable, durable, breathable electrodes based on electrospun polyurethane mats superficially decorated with carbon nanotubes for multifunctional wearable electronics

Abstract

As smart wearable electronics become commonplace, there exists an unmet need for stretchable, durable and breathable electrodes that can be easily integrated with the electronics and comfortable for the users when used for extended periods. Despite the enormous effort in the development of stretchable electronic materials and structures, limited progress has been made in terms of developing a facile, scalable fabrication process to produce mechanically and electrically robust, breathable conductive electrodes for wearable electronics. Herein, we develop a novel stretchable polymer-carbon nanotube composite electrode based on a fibrous polyurethane mat decorated with conductive carbon nanotubes superficially embedded into individual polyurethane fibers. The fibrous polyurethane mat is fabricated through a facile technique of electrospinning, followed by a scalable ultrasonic cavitation treatment in a carbon nanotubes suspension solution. During ultrasonic cavitation treatment, long carbon nanotubes are embedded into electrospun polyurethane fibers and mechanically interlocked with one other, forming a dense, structurally robust, and electrically stable conductive network surrounding each fiber. The as-fabricated electrodes exhibit several superior properties that are characterized by good stretchability (recoverable stretching rate up to 200 %), high conductivity (low sheet resistance of 30 ∼ 50 Ω/sq), excellent stability (over 20,000 bending and stretching cycles), remarkable durability (capable of ultrasonic washing for over 30 min), and efficient air permeability (22.83 mm s−1 at a pressure difference of 100 Pa). Based on the integrated superior performances, the multifunctional capability of this novel electrode for wearable electronics is demonstrated in applications including thin-film heaters, strain sensors, and wearable energy supply of stretchable supercapacitor electrodes. It is supposed that the developed fabrication process and stretchable electrodes could be a versatile platform for development of flexible and wearable electronics.