Highly Elastically Deformable Coiled CNT/Polymer Fibers for Wearable Strain Sensors and Stretchable Supercapacitors

Abstract

Stretchable yarn/fiber electronics with conductive features are optimal components for different wearable devices. This paper presents the construction of coil structure−based carbon nanotube (CNT)/polymer fibers with adjustable piezoresistivity. The composite unit fiber is prepared by wrapping a conductive carbon CNT sheath onto an elastic spandex core. Owing to the helical coil structure, the resultant CNT/polymer composite fibers are highly stretchable (up to approximately 300%) without a noticeable electrical breakdown. More specifically, based on the difference in the coil index (which is the ratio of the coil diameter to the diameter of the fiber within the coil) according to the polymeric core fiber (spandex or nylon), the composite fiber can be used for two different applications (i.e., as strain sensors or supercapacitors), which are presented in this paper. The coiled CNT/spandex composite fiber sensor responds sensitively to tensile strain. The coiled CNT/nylon composite fiber can be employed as an elastic supercapacitor with excellent capacitance retention at 300% strain.

A Review of Yarn-Based One-Dimensional Supercapacitors

“…Linear compression of the coil enabled linear and areal capacitances of 4.8 mF/cm and 22.8 mF/cm 2 , respectively, and the synergistic effect of the coiled and buckled structures imparted outstanding capacitance retention performances of up to 90% under a tensile strain of 800%. Our research group employed commercially available spandex fibers to fabricate the coiled and buckled hybrid fiber structures [ 59 ]. As a result, the prepared fiber supercapacitor could be applied to both fiber-type strain sensors and stretchable fiber supercapacitors, resulting in linear and areal capacitances of 1.12 mF/cm and 11.89 mF/cm 2 , respectively, with a stretchability of 300%.…”

“…Photographs of the bent, pristine, and stretched coiled CNT/polymer fiber (initial length: 1 cm and final length: 4 cm). Reproduced under the terms of the CC BY 4.0 license [ 59 ]. ( c ) Schematic showing the highly twisted CNT-wrapped spandex fiber consisting of the first coil, supercoils, and a buckled surface.…”

Bionic Spider Web Flexible Strain Sensor Based on CF-L and Machine Learning

“…The flexible sensor is composed of surface encapsulation layer, sensitive layer and substrate, of which the sensitive material is the main part of the sensor. At present, the existing sensitive materials have a variety of kinds, including carbon materials, − metal nanoparticles, , conductive fabrics, and liquid metal . Based on the excellent electrical conductivity, large specific surface area, and good biocompatibility of graphene, it shows a better performance than other materials in terms of sensor construction. , …”

Investigation and Improvement of Test Methods for Capacitance and DCESR of EDLC Cells

“…Electrochemical double-layer capacitor (EDLC) cells are a type of emerging electrochemical energy storage device with a high power density of up to 15 kW/kg [ 1 , 2 ], and are widely used in the areas of energy, IoT sensors, wearable strain sensors, electric power, construction machinery, rail transit, automobile transportation, and military [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. The accurate performance characterization of EDLC cells is of great engineering significance to ensure their safety and reliability, especially under the two critical parameters: the capacitance reflecting the capacity to store electric energy and the direct-current equivalent series internal resistance (DCESR) affecting their instantaneous discharge ability.…”