Droplets, vapours and clouds - A new approach to capacitive transducer manufacture

Abstract

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Finite element analysis simulations for ultrasonic array NDE inspections

“…This resulted in a total simulation time of 512 minutes to generate a single FMC dataset. Where suitable hardware is available, employing a parallel architecture could significantly reduce computation time by executing each simulation in parallel [19]. This gives the prospect of a total time of only 4 minutes to generate FMC data for a 128 element phased array transducer.…”

“…This made the computational time required to sequentially generate the FMC dataset very large. Options are available to reduce this through parallelization with a Message Passing Interface (MPI) [20], which was seen to reduce a single run by five times, using PZFlexCloud [19]. The simulations on PZFlexCloud, produced a FMC dataset for a full 3D model in 5 hours.…”

Gas coupled polymeric capacitive transducers via pad printing

“…Previous work by the author has indicated that for aircoupled operation, an orthogonal layout of 700nm deep, 500μm diameter cavities on a 1000μm pitch will result in a 500kHz operation in air [6]. Matlab was used to create the design, a 20mm circular aperture comprising 500μm diameter planar tipped styli on a 1000μm pitch.…”

“…Polystyrene absorbs toluene causing it to swell, however regions of polystyrene under the deposited droplets do not absorb toluene and hence the do not swell thus forming small cavities. The period of time the sample is exposed to the toluene vapor governs the extent of the swelling and hence depth of the cavity [5], [6]. After exposure to toluene vapor, the sample is air dried at 20 O C and 500μm then washed by sonication in methanol to remove the PEG droplets and further air-drying at 20 O C. In order to manufacture transducers, the polystyrene substrate is then electroded on all faces with silver using an electroless process with a tin sensitizer [7].…”

“…Typical MSL constructed devices tend to be limited to low operating frequencies <200kHz [3], [4] -a consequence of the available voxel size in the MSL process. More recently, the author has reported a new process for the manufacture of cavities within cMUT devices [5], [6]. Deposition of a positive mask onto a polymer substrate which is subsequently exposed to a vapour of solvent, which is absorbed into the substrate allows for controlled formation of cavities.…”