Fig. 5: Special PMUTs which can be classified as follows.
From: Thin-film PMUTs: a review of over 40 years of research
a Structurally modified PMUTs: (i) bimorph PMUT with enhanced transmit sensitivity54; (ii) PMUT with venting rings and enhanced transmit sensitivity55; (iii) curved PMUT with increased pressure output56; (iv) PMUT with relaxed boundary conditions57; (v) PMUT with isolation trench and enhanced sensitivity60; (vi) PMUTs with V-shaped rings61; (vii) broadband PMUTs62; (viii) central and annular PMUTs on a single chip65; (ix) ring-shaped PMUT66; and (x) Archimedean PMUT array67. b Flexible PMUTs: (i) polymer PMUT72; (ii) fully flexible PMUT53; and (iii) flexible PMUT die with rigid elements52. All pictures have been adapted with permission
