Fig. 4: A 3D imaging meta-lens via BC meta-skin paper-cutting.

a Graphite rods for 3D ultrasonic imaging, for which the diameter is 200 μm. The graphite rods are set to position in three planes (1, 2, 3) with different orientations for testing the longitudinal resolution, and the projection forms a hexagram pattern. Inset shows an imaging meta-lens based on BC meta-skin paper-cutting. b The ultrasonic images of graphite rods with different depths (b1, b2, b3). Here the 3D ultrasonic images are reconstructed by extracting and arranging the echo signal data. c 3D reconstruction image of graphite rods. d 3D-printed metal patterns ‘HUST’ and ‘SIAT’ for 3D ultrasonic imaging. The distance between the two patterns is 900 μm. The horizontal shift between letters ‘T’ is 200 μm for testing the transverse resolution. e Reconstructed images of ‘HUST’ and ‘SIAT’ at the depths of e1, e2. f Intensity profiles extracted on the dashed lines (e1, e2) in (e). We also show the superimposed result of e1+e2.