An Automated Microsurgery System for Embryo Biopsy

• Main Author: Bait Bahadur, Issam M.
• Other Authors: Mills, James
• Language: en_ca
• Published: 2013
• Subjects: Autofocusing; PGD; Vision; Hysteresis; needle; embryo
• Online Access: http://hdl.handle.net/1807/35772

Embryonic biopsy routinely involves the removal of one or two blastomeres in the preimplantation genetic diagnosis (PGD) procedure to determine the presence of a specific disease. The rapid development of the PGD technique and stem cell research has led to great demand for highly automated high precision equipment for cellular component micro-extraction. This thesis presents the development of an automated microsurgery system for embryo biopsy. While the ultimate objective of this research is to improve the so called “take-home-baby rate”, the primary focus of this research, however, is devoted to demonstrate the automation of the first two steps in the embryo biopsy procedure: embryo immobilization and embryo perforation with a piezoelectric actuated micro-cutter mounted on a five DOF micromanipulator. A biological embryo holding device incorporating a unique configuration of fluidic channels is designed to increase embryo mobility in order to overcome friction force while maintaining a low suction flow rate and pressure. The validity of this design is demonstrated by good qualitative agreement between the experimental and simulation results. 3D nonlinear equations of motion of a micro-needle driven longitudinally by a piezoelectric actuator are developed based on Kane’s method . The longitudinal vibration of a micro-needle results in excitation of its out-of-plane, lateral eigenmodes at low damping coefficients. The dynamic model is in good agreement with experimental observations. This model is exploited further to describe the response of an immersed glass micropipette with imbedded mercury in piezo-assisted intracytoplasmic sperm injection (ICSI). Furthermore, piezoelectric actuator dynamic nonlinearity introduced by hysteresis is addressed in this research. A new model is proposed to characterize the rate-dependent hysteresis based on Duffing's equation. A nonlinear capacitor element is incorporated into a linear second-order system to predict the relationship between an input state and a hysteretic output. The proposed hysteresis model is verified experimentally. Based on this approach, a new electromechanical piezoelectric actuator model is proposed. A vision-assisted controller for embryo perforation is proposed by implementing a vision tracking and robust autofocusing algorithm using the particle swarm optimization (PSO) method. The performance of the proposed visual-based controller demonstrated experimentally to be effective in providing accurate embryo and micro-needle 3D positioning. Finally, an automated embryo perforation with the proposed mechanical approach was conducted successfully.