A new strain gauge based on graphene piezoresistivity was fabricated by a novel low cost technique which suits mass production of micro piezoresistor sensors. The strain gauge consists of a monolayer graphene film made by chemical vapor deposition on a copper foil surface, and transferred to Si/SiO2 surface by using a polymethyl-methacrylate (PMMA) assisted transfer method. The film is shaped by laser machine to work as a conductive-piezoresistive material between two deposited electrical silver electrodes. This method of fabrication provides a high productivity due to the homogeneous distribution of the graphene monolayer all over the Si/SiO2 surface. The experimentally measured gauge factor of graphene based device is 255, which promises a new strain gauge sensor of high sensitivity.

Monolayer and multilayer graphene films have been grown on a Cu substrate by chemical vapor deposition (CVD) and then transferred onto a SiO 2 /Si substrate using polymethyl methacrylate (PMMA) to fabricate an ultrasensitive graphene-based strain gauge sensor. The graphene films were patterned using a CO 2 laser beam. The sensitivity and temperature dependence of the gauge factor (GF) of the fabricated sensors were examined at different applied strains and operating temperatures up to 0.05% and 75 °C, respectively. The fabricated gauges based on monolayer and multilayer graphene films show stable GFs of 255 and 104 within the applied temperature range, respectively. The patterning technique provides an interesting, lowcost, fast, and high-throughput process to realize scalable microfabrication for highly sensitive strain sensors with good temperature stability based on graphene piezoresistivity. A theoretical simulation of the GF of monolayer graphene has also been carried out on the basis of firstprinciples calculation. Simulation results follow the measured GFs in our experiment and other references. *. The data are averaged for all angles (0° ≤ θ < 360°).

Purpose The purpose of this paper is to develop a new simple technique to synthesize graphene film on a flexible polyethylene terephthalate (PET) substrate and applied as a strain sensor. Design/methodology/approach Graphene film was synthesized using laser treatment of graphene oxide (GO) film deposited on PET substrate. A universal laser system was used to simultaneously reduce and pattern the GO film into laser reduced graphene oxide (LRGO) film. Findings The laser treatment synthesizes a multilayer graphene film with overlapped flakes, which shows structure integrity, mechanical flexibility and electrical conductivity of 1,330 S/m. The developed LRGO/PET film was used to fabricate a high sensitivity strain sensor. The sensitivity and temperature dependency of its gauge factor (GF) was examined at applied strains up to 0.25 per cent and operating temperatures up to 80°C. The fabricated sensor shows stable GF of approximately 78 up to 60°C with standard error of the mean not exceeding approximately ± 0.2. Originality/value The proposed method offers a new simple and productive technique of fabricating large-scale graphene-based flexible devices at a low cost.

New technique is developed to synthesize graphene film on flexible substrate for strain sensing applications. A flexible graphene/Poly-ethylene Terephthalate (PET) strain sensor based on graphene piezoresistivity is produced by a new simple low cost technique. Graphene oxide film on PET substrate is reduced and patterned simultaneously using 2 Watt CO2LASER beam. The synthesized graphene film is characterized by XRD, FT-IR, SEM, and Raman techniques. Commercial strain gauges are used to predict experimentally the gauge factor (GF) of the graphene film at different values of applied strain. The stability of the graphene film and its GF are studied at different operating temperatures. The fabricated sensor showed high GF of 78 with great linearity and stability up to 60 °C.

The piezoresistive effect in graphene ribbon has been simulated based on the first-principles electronic-state calculation for the development of novel piezoresistive materials with special performances such as high flexibility and low fabriccation cost. We modified theoretical approach for piezoresistivity simulation from our original method for semiconductor systems to improved procedure applicable to conductor systems. The variations of carrier conductivity due to strain along with the graphene ribbon models (armchair model and zigzag model) have been calculated using band carrier densities and their corresponding effective masses derived from the one-dimensional electronic band diagram. We found that the armchair-type graphene nano-ribbon models have low conductivity with heavy effective mass. This is a totally different conductivity from two-dimensional graphene sheet. The variation of band energy diagrams of the zigzag-type graphene nano-ribbon models due to strain is much more sensitive than that of the armchair models. As a result, the longitudinal and transverse gauge factors are high in our calculation, and in particular, the zigzag-type graphene ribbon has an enormous potential material with high piezoresistivity. So, it will be one of the most important candidates that can be used as a high-performance piezoresistive material for fabricating a new high sensitive strain gauge sensor.