Patterned piezoelectricity in charged, cellular polymers for air-borne ultrasound devices

Soft, flexible and sensitive piezoelectric materials are in demand for applications, like piezoelectric phased arrays for direction sensitive acoustic wave detection and emission. Here we report on air-borne ultrasound generation with novel piezoelectric polymers: charged, cellular polypropylene foams from VTT Chemical Technology. Based on polymer foams, two focusing devices have been developed and acoustically characterised: spherical acoustical sound generators and acoustical Fresnel zone plates. Both devices may pave the way for simple tools for non-destructive materials inspection.