Realization of Closed Cavity Resonator Formed by Graphene-PMMA Membrane for Sensing Audio Frequency

Abstract

Large area graphene-poly (methyl methacrylate) (PMMA) closed cavity resonator has been fabricated. The resonator has been formed by transferring an ultra-large graphene-PMMA membrane over 3.5 mm diameter circular closed cavity with 220 µm depth. The graphene-PMMA membrane includes 6-layer graphene and 450 nm PMMA film. A modified graphene-PMMA dry transfer method has been developed in this work. Using the Kapton tape supporting frame, the graphene-PMMA membrane has been dry transferred onto the substrate with a small membrane's static deformation of around 180 nm. The membrane's static deformation aspect ratio (suspended membrane's diameter over the membrane's deformation) is around 19,500. The graphene-PMMA closed cavity resonator has been actuated mechanically, acoustically and electro-thermally. The dynamic behaviour of the membrane suspended over the closed cavity shows that the (1, 1) mode dominates the graphene-PMMA membrane's resonance with a resonant frequency of around 10 kHz and suggests the device is under good gas encapsulation. Acoustic vibration amplitude sensitivity of graphene-PMMA membrane over the closed cavity is measured to be around 6 µm/Pa. The membrane's dynamic behaviour, simulated under similar mechanical and electro-thermal actuation conditions, has been shown to be consistent with the trend of the device's experimental results. The strain in the suspended graphene-PMMA membrane is estimated to be 0.04 ± ± ± 0.01 % % %.

Realization of a Graphene/PMMA Acoustic Capacitive Sensor Released by Silicon Dioxide Sacrificial Layer

“…26 A DC voltage of 0.01 V has been applied to this work, which is supposed to minimize the electrical softening, compared to our work. 19,25 In the suspended graphene/PMMA structure, the built-in tension dominates the overall tension. 19,25 The decrease in the overall tension (N i + N a ) in this work might indicate that using the silicon dioxide sacrificial layer compensates the built-in stress generated in the graphene-transfer method.…”

“…The total tension in the graphene/PMMA membrane under electrostatic actuation has been calculated with eq , and the results are shown in Table . In our other work, , the bilayer membranes have been suspended over the same cavity diameter, but the graphene-transfer methods are different. In comparison to similar samples actuated electrothermally by 1 V AC and 1 V DC, , the tension and strain in this work are the minimum.…”

“…In our other work, , the bilayer membranes have been suspended over the same cavity diameter, but the graphene-transfer methods are different. In comparison to similar samples actuated electrothermally by 1 V AC and 1 V DC, , the tension and strain in this work are the minimum.…”

“…However, for sensing audio frequency (20 Hz to 20 kHz), the diameter of the graphene-based membrane reported in graphene-based acoustic sensors has been required to be a few millimeters (3.5–7 mm). − Considering that the multi-layer graphene membrane is about a few atoms thick, it is challenging to transfer graphene due to the large aspect ratio of the membrane. So far, there have been a few acoustic applications based on graphene. − In recent research, the graphene membrane has been thickened by increasing the graphene layer number ranging from 67 to 1800 or by attaching 200 nm or micrometer thick poly­(methyl methacrylate) (PMMA) in order to increase the stability of the devices. A 10-layer graphene diaphragm with up to a 4 mm diameter has been fabricated but with a complex vacuum-assisted sublimation transfer method .…”

Stress-strain in electron-beam activated polymeric micro-actuators

“…Our calibration is relevant not only for applications of polymer-based strain engineering, but also for any device whose behavior is affected by stress transfer at the interface between a polymeric layer and a 2D material [16,17,18]. Applications go from the use of cross-linked PMMA as an anchorage for mechanical resonators [19] or for composite graphene/PMMA suspended membranes [20] up to stretchable/wearable devices [21,22,23], where the shear forces and sliding between a 2D material and its soft substrate are particularly relevant.…”