  We design an impedance matching underwater acoustic bend with pentamode
microstructure. The proposed bend is assembled by pentamode lattice. The
effective density and compressive mod- ulus of each unit cell can be tuned
simultaneously, which are modulated to guarantee both the bending effect and
high transmission. The standard deviations of transmitted phase are calculated
to quantitatively evaluate the degree of the distortion of the transmitted
wavefront, while the trans- mission is calculated to appraise the degree of
acoustic impedance matching. The low standard deviations and high transmission
indicate that the designed bend has a nice broadband bending effect and is
impedance-matched to water. This design has potential applications in
underwater communication and underwater detection.
