Towards a locally constructed multi-element ultrasound imaging transducer for resource poor environments

This paper investigates techniques and materials for making a multi-element ultrasound imaging transducer with craft-based techniques available in resource poor environments. The transducer housing can be conveniently divided into three parts: the body supporting the piezoelectric (PZT) elements and other components; the matching layer between the PZT elements and the human body; and the backing layer behind the PZT elements. Low-cost 3D printing systems based on photopolymers were found to be suitable for manufacturing the body. Finite Element Modelling (FEM) showed that the material characteristics of the backing layer and the thickness of the matching layer were much less critical than predicted by ultrasound plane wave theory and transmission line theory, respectively. The backing and matching layers are normally made from epoxy-tungsten composites that are pourable in the uncured state. However, the composite required for the backing layer was putty-like when uncured. When the tungsten was allowed to settle under gravity during curing, a 20 % by volume uncured tungsten-epoxy composite gave a 30 % by volume concentration of tungsten at the bottom when cured at 20–30 °C. These findings, when coupled with the findings from the FEM modelling, suggests that constructing a multi-element ultrasound imaging transducer using craft-based techniques is feasible.