Micro rotary-linear actuator assisted by ferrofluid levitation for 3-dimensional endoscopic imaging

This paper reports the first microactuator that selectively and simultaneously produces rotational and linear motions of its rotor/slider targeted at applications for minimally invasive active catheters. The magnet rotor/slider component is levitated by ferrofluid accumulated around it inside a catheter tube, achieving low-friction actuation for electromagnetic rotation of the component and/or its pneumatic sliding along the tube´s axis. A microfabricated prototype of the actuator is coupled with a prism mirror to demonstrate full 3-dimentional (3D) scanning of an energy beam, verifying the designed functionality of the actuator. Testing of the prototype reveals a superior axial stability of rotation over the preceding device with no linear actuation function. The results indicate a promising potential for circumferential 3D imaging usable for different types of endoscopic imaging including ultrasound and optical coherence tomography.