Effects of Sample Adhesives Acoustic Properties on Spatial Resolution of Pulsed Electroacoustic Measurements

The media chosen to couple the PEA stack (electrode/sample/sensor/backing) can affect the spatial resolution and shape of the response from a Pulsed Electroacoustic (PEA) system significantly. The PEA stack layers must be electrically and acoustically coupled to optimize the amplitude, quality, and spatial resolution of the PEA measurements. Various coupling layer materials were used with 250 μm thick polymethylmethacrylate (PMMA) samples and a standard ~10 μm thick PVDF sensor. Coupling layers tested in this study include no media (with substantial pressure applied), light machine oil, silicone oil, and cyanoacrylate (super glue). Pulse amplitudes of 2000 V and 5 ns width were used. Static 8 kV DC bias was applied to the sample in order to detect a signal, as the samples were initially free of charge, and to see the interfaces more clearly and showcase the differences in response from the various coupling media. The best option was found to be a single layer of cyanoacrylate at the ground electrode-sample interface; this is the only viable option for in vacuo PEA measurements of the media tested.