Microfabrication and evaluation of piezoceramic actuators

Abstract: There is an increasing interest for miniaturised actuators in a number of technological fields such as automation or medicine (e.g. prostheses, medical pumps etc.). The focus of the thesis work has been the development of fabrication techniques for miniaturised piezoceramic actuators and actuator systems, Different piezoceramic actuators has been fabricated and evaluated.For a piezoelectric motor an analytic model has been derived and confirmed to agree with a macroscopic prototype. A piezoelectric miniature motor (Ø 4 mm) has been developed and characterised. A reasonable agreement with the derived analytical model is shown. The maximum output torque and rotational velocity was 1.4 mNm and 4.2 rpm. An improved design of the piezoelectric miniature motor gave enhanced performance and a maximum output torque of 3.8 mNm and a rotational velocity of 65 rpm were achieved. Those values are among the highest presented for miniature motors of this size.One of the most realistic fabrication techniques for complex piezoceramic actuator systems is assembling. Two methods are presented, one is suitable for high precision assembly and the other when moderate precision is needed. Miniaturisation of multilayer ceramic actuators puts high demands on the techniques used for patterning of electrode layers. A new technique for high resolution patterning of electrode layers on ceramic green bodies is presented. By embossing, line widths and spacings as low as 20 µm have been accomplished. To comply with the embossing technique a wet building process for multilayer ceramic actuators has been developed.

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