Wide‐Area Strain Sensors based upon Graphene‐Polymer Composite Coatings Probed by Raman Spectroscopy

Abstract

Functional graphene optical sensors are now viable due to the recent developments in hand-held Raman spectroscopy and the chemical vapor deposition (CVD) of graphene fi lms. Herein, the strain in graphene/poly (methyl methacrylate) sensor coatings is followed using Raman band shifts. The performance of an "ideal" mechanically-exfoliated single crystal graphene fl ake is compared to a scalable CVD graphene fi lm. The dry-transferred mechanically exfoliated sample has no residual stresses, whereas the CVD sample is in compression following the solvent evaporation during its transfer. The behavior of the sensors under cyclic deformation shows an initial breakdown of the graphene-polymer interface with the interface then stabilizing after several cycles. The Raman 2D band shift rates per unit strain of the exfoliated graphene are ≈35% higher than CVD graphene making the former more strain sensitive. However, for practical wide-area applications, CVD graphene coatings are still viable candidates as a Raman system can be used to read the strain in any 5 µm diameter spot in the coating to an absolute accuracy of ≈0.01% strain and resolution of ≈27 microstrains (µs), which compares favorably to commercial photoelastic systems.

Graphene/elastomer nanocomposites

“…It has been found that the rate of band shift per unit strain can be associated with the Young modulus of carbon fibres [89,90] and other high-performance fibres [89,91]. In a similar way it has been shown that the deformation of graphene leads to lattice distortion and bond stretching, which ultimately affect its properties [45,90,[92][93][94][95]. From the slope of the values of the Raman wavenumbers versus strain, the modulus of elasticity for monolayer graphene is calculated, using carbon fibres as a calibration, to be equal to 1000 ± 100 GPa [90], similar to values measured directly [31].…”

An experimental investigation on the tangential interfacial properties of graphene: Size effect

“…Varisized graphene materials have been widely applied to the new domain of microelectronic devices, such as flexible electronic components, ultra-sensitive strain sensors and battery electrodes [1][2][3]. The quality and performance of these devices are often limited by the mechanical properties and the deformation transmission efficiency of the interface between graphene and the substrate or surrounding material.…”

Theoretical investigations of the interfacial sliding and buckling of graphene on a flexible substrate

“…Graphene, a two-dimensional (2D) monolayer nanomaterial, has attracted significant attention in recent decades because of its unique electronic, thermal, and mechanical properties, and it is considered to have promising applications in the fields of nano-electronics, [1][2][3][4] flexible/stretchable electronics, 5,6 and nanocomposites, [7][8][9] etc. In graphene-based stretchable electronics and graphenereinforced nanocomposites, the interfacial failures between graphene and substrate materials is the main factor limiting their overall performance and reliability.…”