Hybrid strategy of graphene/carbon nanotube hierarchical networks for highly sensitive, flexible wearable strain sensors

Abstract

One-dimensional and two-dimensional materials are widely used to compose the conductive network atop soft substrate to form flexible strain sensors for several wearable electronic applications. However, limited contact area and layer misplacement hinder the rapid development of flexible strain sensors based on 1D or 2D materials. To overcome these drawbacks above, we proposed a hybrid strategy by combining 1D carbon nanotubes (CNTs) and 2D graphene nanoplatelets (GNPs), and the developed strain sensor based on CNT-GNP hierarchical networks showed remarkable sensitivity and tenability. The strain sensor can be stretched in excess of 50% of its original length, showing high sensitivity (gauge factor 197 at 10% strain) and tenability (recoverable after 50% strain) due to the enhanced resistive behavior upon stretching. Moreover, the GNP-CNT hybrid thin film shows highly reproducible response for more than 1000 loading cycles, exhibiting long-term durability, which could be attributed to the GNPs conductive networks significantly strengthened by the hybridization with CNTs. Human activities such as finger bending and throat swallowing were monitored by the GNP-CNT thin film strain sensor, indicating that the stretchable sensor could lead to promising applications in wearable devices for human motion monitoring.

Crack engineering boosts the performance of flexible sensors

“…By blending 1D CNTs with 2D graphene nanoplatelets (GNP), a GNP/CNT hybrid film, which possessed the characteristics of lowdimensional structures and initiated cracks among GNPs during stretching, was prepared. 46 Differently, the CNT dispersion showed relative sliding and functioned as the bridges among cracks, which could reconnect the broken GNPs under large strain and maintain a conductive path (Figure 5A), overcoming the defect in highly sensitive graphene strain sensor that the conductive network could be irreversibly damaged under small strain (7%). As a result, the optimized sensor realized a GF as high as 197 in a strain range of 10%, and possessed an excellent stretchability of over 50%.…”

“…Reprinted with permission. 46 Copyright 2021, Springer Nature. (B) Microcrack sensing models for reduced graphene oxide (rGO) strain sensors and rGO/polydopamine (PDA)/Ni strain sensors.…”

Carbon nanotube-graphene hybrids for soft electronics, sensors, and actuators

“…Li et al reported graphene nanoplatelets and CNTs forming hierarchical hybrid networks fabricated by spray coating. These were demonstrated in flexible wearable strain sensors by applying them to a human finger and front neck area [92]. In general, the enhanced sensitivity of the graphene from introducing the CNTs allows for the detection of subtle motions.…”

Quantitative Performance Analysis of Flexible Ink-jet Printed Low-cost DNA Sensors Based on a CNT Network

“…Ink-jet printing has recently emerged as a potential route for developing miniaturized, low-cost, flexible sensors based on nanostructure network array for various personal health, biological, and environmental sensing [1]- [8]. In this regard, carbon-based nanomaterials such as carbon nanotubes (CNTs) and graphene have been extensively investigated as response components in ink-jet printed flexible biosensors due to their unique electrical and mechanical properties [1], [7], [9]- [12]. Biosensors utilize several readout methods which are based on either optical or mechanical based transduction methods, however, these methods are bulky due to the integration of various optical sources and detectors and therefore increase the total system cost [13]- [16].…”