Graphene: Diversified Flexible 2D Material for Wearable Vital Signs Monitoring

Abstract

Flexible wearable sensors are expected to be the future generation of personal health monitoring devices with large‐area, multimodal, multipoint sensing, and complicated data analysis. However, multimaterial interfacial coalescence and mechanical matching critically challenge the advancement of flexible devices and multifunction integration. Graphene, with characteristic carbon sheet 2D material, is endowed with good transparency, stability, superior electron mobility, heat conductivity, excellent flexibility, and mechanical performance. A summary of the progresses of flexible graphene‐based sensors in terms of material processing, sensor configuration, and property is presented. Various assembly structures could perform different electrical behaviors with unitary graphene material. The diversity of graphene‐based temperature, humidity, pressure, strain, and integrated multifunctional sensors developed in recent years is detailed. Benefitting from the commendable flexible mechanical performance and high durability, flexible graphene‐based sensors promote practical applications in body temperature monitoring, voice recognition, pulse‐beating, motion, and respiration detection. Finally, future research following the development trends and challenges of integrated graphene‐based sensors to develop their potential in human health monitoring and human–machine interfaces are discussed.

Graphene Nanostructure-Based Tactile Sensors for Electronic Skin Applications

“…On one hand, the inherent characteristics of graphene and its derivatives, such as a large surface area and planar geometry, good electrical conductivity (ultrahigh mobility, ballistic transport, anomalous quantum Hall effect, nonzero minimum quantum conductivity, Anderson weak local change, and Klein tunneling), high chemical and thermal stabilities, and low toxicity, as well as being readily functionalizable, enable the effective detection of various stimuli [6][7][8][9][10]. On the other hand, additional unique superiorities, such as their lightweight, mechanical flexibility, and generally good processability, as well as their good compatibility with large-area and flexible solid supports, endow these materials with great potential for the manufacturing of sensing devices using a wide range of desirable or arbitrary solid supports [11][12][13][14][15]. Furthermore, diverse assembly and processing approaches, such as chemical modification, interfacial assembly, nanodoping, layer-by-layer assembly, laser scribing, dip-coating and others, can be employed to obtain graphene materials with new functions.…”

Research Progress of Graphene-based Flexible Sensor in Wearable Health Monitoring

“…It can solve many problems in the practical application of intelligent wearable devices. Wearable technology develops rapidly, but there are still many problems in practical application [45]. Firstly, the use of graphene and composite materials and the preparation technology of sensors are the research focus.…”

“…To overcome this shortcoming, graphene can be compounded with flexible materials, such as biocompatible materials and high-functional carbon-based materials. Or the design of a structure with high sensitivity, such as spider web structure, serpentine structure, porous structure and coiled fiber structure, is of great significance for the practical application of Graphene-based sensors in wearable health monitoring [40,41].…”

Two‐dimensional materials: From mechanical properties to flexible mechanical sensors

“…Atomically thin two‐dimensional (2D) materials have attracted a large amount of attention in the past few years due to their unique and excellent electric, optical, magnetic, and mechanical properties since graphene was obtained successfully by micromechanical cleavage from graphite in 2004 . As a monolayer atomic carbon of crystal, graphene has shown high thermal conductivity (3000‐5000 W m −1 K −1 ), an excellent optical transparency of 98%, and an extremely high Young's modulus of 1 TPa . Meanwhile, it can bear strains of more than 25% without fracture .…”