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Vector Controlled Ultrasonic Transducer Applied to Soft Material Mechanical Impedance Estimation

The study of skin mechanical impedance is a clue to analyse its health. We use a Langevin Transducer at 60kHz to excite the skin. In return we observe the acoustic forces generated by the interaction. To achieve that, the system is identified and presented in the rotating reference frame, and we describe the design of two PI controllers that accurately control the vibration velocity. However, in vivo analysis can be tricky when it comes to safety and duration of tests. Thus, phantom tissues are used as substitute to simulate skin behaviour. Due to its mechanical properties similar to skin, and its simple manipulation, Dragon Skin ®, a silicone rubber type of phantom, was chosen. The paper presents the characterisation of the mechanical impedance of three silicon phantoms with different properties based on force observation. The results show that the phantoms can be indeed identified based on this method.