Design and applications of graphene-based flexible and wearable physical sensing devices

Abstract

The rise of human–machine interaction and the internet of things technology requires the development of functionalized sensors that are mechanically flexible and fabulously wearable. Therefore, the emergence of new materials and devices is particularly important for technology design and development. Graphene has the atomically level thickness, mechanical flexibility, lightweights, and high conductivity and transparency. Especially, the large specific area of graphene enables the perception of external stimuli with high sensitivity, which is expected to be used in flexible sensor technology. In this review, we will introduce the research progress of graphene in flexible physical signal sensors, including the device structure design and the applications of these devices in wearable technology. We will overview the development of new directions of sensors, such as miniaturization, intelligence, and multi-modal. We will also focus on the latest technical progress of related sensing devices and point out the challenges and directions of future development of wearable sensors.

Quantifying the Piezoresistive Mechanism in High-Performance Printed Graphene Strain Sensors

“…This parameter is one of the most important and certainly the most studied in piezoresistor research. However, for sensors to be useful, as well as having high G , they also need to have a good linear range, low load/unload hysteresis, and minimal variation of G with frequency. − Ideally, they would also be relatively easy to fabricate and install where needed. − In terms of commercial sensors, while metal foil strain gauges are relatively cheap and simple to produce, these have a relatively low G -value of ∼2 as the resistance change is based entirely on geometric changes …”

“…Much effort has been made to develop sensors with gauge factors well beyond G ≈ 2. Many researchers have turned to materials science to fabricate sensing materials with high G -values while minimizing negative properties such as hysteresis and frequency dependence. − , Nanocomposites have shown great promise due to their versatility and the ability to tune sensor response by varying the matrix, the filler, and the composition , with hundreds of papers reporting results for piezoresistive nanocomposites with gauge factors as high as 2600 . However, composite sensors have a number of limitations: for example, the conductivity can be low, partly due to polymer coatings around the conducting filler particles .…”

Graphene Synthesis Techniques and Environmental Applications

“…Thanks to their superior characteristics such as excellent thermal, electrical, mechanical, and optical properties, graphene-based materials have also been widely used in electronic applications. Furthermore, graphene and its derivatives have also seen enormous applicability in optical devices including photodetectors, electronic sensors, light-emitting diodes (LEDs), and other applications including temperature sensors, transducers, thermoelectric sensors, and energy-management systems [ 119 , 120 , 121 ].…”

Untitled Document

“…The flexible devices in flexible electronic equipments are made by using printing technology and connecting various functional components (6). The choice of ink depend on different applications in flexible devices (7)(8)(9). Conductive ink can be divided into organic conductive ink, inorganic conductive ink and composite conductive ink according to the types of conductive fillers (10)(11)(12).…”