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UBC Theses and Dissertations

A ferrofluid-assisted planar micromotor for endoscopic multimodal imaging Searles, Kyle


Optical endoscopy is a common technique for diagnosing and treating disease given its ability to analyze tissue in real time and in a non-destructive manner. There are many different imaging modalities used in endoscopes, with common ones being white light endoscopy, optical coherence tomography (OCT) and Raman spectroscopy. Each modality provides fundamentally different information, while white light endoscopy works just like a visual camera, OCT provides high resolution cross-sections, and Raman spectroscopy provides chemical composition data. For these imaging modalities, the optical path needs to be circumferentially rotated to provide a full 360° field-of-view, with each modality requiring a different rotation scheme (e.g., Raman spectroscopy requires stepping and OCT requires high speed). Rotating the beam using a micro distal scanner embedded at the tip of an endoscope is a way to improve the image quality. This work proposes a hollow and planar ferrofluid-based micro actuator that can be actuated in both a stepping and highspeed manner, which enables a distal scanner usable for multimodal imaging. Compared to preceding tubular designs, the planar topology allows for downsizing in the actuator’s axial size, which helps preserve probe flexibility. Furthermore, the hollow design provides an unobstructed optical path through the actuator body, which removes imaging blind spots. The novel design is first prototyped to prove its ability to act as an optical scanner by using flex-circuit microfabrication and 3D printing techniques to manufacture it. The prototype is successfully driven to revolve the rotor with 45 steps on a ring-shaped planar stator, which are then cycled at high frequencies to continuously spin the rotor. The proof-of-concept actuator was then coupled with fiber optic terminated with a gradient-index (GRIN) lens to allow for real time OCT imaging of a human index finger and thumb. The acquired images had no shadows from the electrical wiring and were of high enough quality to differentiate skin layers and make out sweat glands.

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