Fig. 1: PillarWaveTM technology.
a Confocal microscope image of the P(VDF-TrFE) film directly after embossing. b Schematic cross section of the flexible ultrasound transducers. On top of a polyimide foil (thickness 14 μm) and a patterned molybdenum-aluminum electrode (500 nm thick) a ca. 40 μm P(VDF-TrFE) film is embossed resulting in 3D structures that are ca. 70 μm high with a residual layer of ca. 10 μm below. On top of the 3D structures, a 10 μm P(VDF-TrFE) film is laminated at elevated temperatures, whereafter a 500 nm molybdenum-aluminum top-electrode is deposited. The stack is finished with an isolating and flexible encapsulation film. c Side view of the complete transducer after lamination of the top electrode. The white areas are the P(VDF-TrFE) film. The orangish areas are air-filled gaps between the pillars. d Photograph of the finished ultrasound transducer foil, illustrating its thinness of 0.1 mm and mechanical flexibility. e Transducer foil wrapped around the inner wire of a dilatation catheter for percutaneous transluminal angioplasty (PTCA) (Blue Medical Force NC) that has a radius of 0.25 mm for intravascular ultrasound. f Ultrasound transducer foil placed in the neck on top of the carotid artery for blood pressure measurements.
