Thermo-formed piezoelectrets with open-tubular channels produced from water-filled FEP pads

In this work an alternative method for producing piezoelectrets with open-tubular channels is presented. The method consists of compressing two heated stamped metal plates over a water-filled pad prefabricated with fluoroethylenepropylene (FEP) films. During hot compression the heated water increases the pad internal pressure, helping to mold the FEP film over the metal stamped pattern. A corrugated pattern was used to create piezoelectrets with open-tubular channels similar to those previously reported in the literature, however, in this process instead of discarding a polytetrafluorethylene (PTFE) template water vapor is released. Some previous results obtained with these piezoelectrets regarding temporal stability, charging conditions and measurements performed under different pressures are also presented.