Two problems in biomedical engineering: Design of surgical tools for an ocular implant and the effects of leg morphology on running performance

James Bradley Lohmeyer, Purdue University

Abstract

Part I: Surgical Tool Design. The primary objective of this thesis was the development of a surgical tool to implant a specialized micro-scale sensor into the anterior chamber of a mouse eye. The sensor measures intra-ocular pressure continuously under normal living conditions, creating a measurement system that is needed in the field of Glaucoma research. The sensor has a complex geometry comprised of both compliant and non-compliant materials, and requires careful handling. Previously, the surgical procedure required three separate tools; a knife, a syringe and needle, and forceps. That procedure suffered from issues of ease of use, efficiency, safety and reliability. The objective was to design, fabricate, and test a single unified tool that could perform all necessary surgical functions. The motivation for unifying the toolset into a single device was primarily to improve surgical efficiency and ease of use. The development of the surgical tool faced a number of different challenges. These issues pertained to creating a sharp cutting instrument within unusual geometrical constraints, loading the sensor into a narrow tube, delivering both fluid and an object through the same tube, optimizing dimensions against competing constraints, and satisfying the ergonomic needs of the surgeon. Two generations of prototypes were fabricated and tested. The second generation prototype was comprised of three telescoping tubes, each with a specific function. All three surgical steps were successfully carried out on a cadaver pig eye, with minor complications in the handling of the tool. Due to inherent design constraints in the implant and available materials, the size of the tool is likely more appropriate for the anatomy of a larger animal. Part II: The Effects of Leg Morphology on Running Performance. The secondary objective of this thesis was to explore how differences in joint morphology impact the dynamics and energetics of running. An analysis was completed on the effects of kinematic knee orientation on legged locomotion, specifically simple running patterns. The analysis compared the dynamics of a forward facing knee found in humans, a rear facing ankle found in birds, and a linear knee found in pogo sticks and simple robots. The equations of motion for the models reveal that joint orientation has a direct effect on the dynamics of the system. The early simulation results show that leg morphology directly effects deflection and force patterns, which in turn effects the trajectory of the system. In forward facing joints, hip torque increases ground reaction forces, creating the appearance of higher compliance in the leg. In rear facing joints, hip torque decreases ground reaction forces, creating the appearance of lower compliance in the leg. The results suggest that a forward facing knee joint found in humans is more energy efficient than a rear facing ankle joint found in birds.

Degree

M.S.M.E.

Advisors

Seipel, Purdue University.

Subject Area

Biomedical engineering|Mechanical engineering|Kinesiology|Surgery|Biomechanics

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