Needles are commonly used to reach target locations inside of the human body for various medical interventions such as drug delivery, biopsy, and brachytherapy cancer treatment. The success of these procedures is highly dependent on whether the needle tip reaches the target. One of the most significant contributors to the target accuracy is the needle insertion force that causes needle-tip deflection, tissue deformation, and tissue damage. Recently there has been tremendous interest in the medical community to develop innovative surgical needles using biologically-inspired designs. It is well known that insects such as honeybee and mosquito steer their stingers effortlessly to a specific target and release their venom in a certain path through the skin with minimal force. These unique traits inspire this dissertation work to develop bioinspired needles and to study the insertion mechanics of these needles for reducing the insertion force, needle-tip deflection, tissue deformation, and tissue damage. In this work, the insertion mechanics of honeybee-inspired needles with applied vibration in polyvinyl chloride (PVC) tissue phantom and chicken breast tissues was first investigated. It was observed that the insertion force was decreased by 43% and the needle tip deflection was minimized by 47% using honeybee-inspired needles. Furthermore, the insertion mechanics of mosquito-inspired needles in PVC tissue phantom and bovine liver tissues were studied. Design parameters such as maxilla design on the needle body, labrum-tip, vibration, and insertion velocity were considered. It was found that the insertion force was reduced by 60% in PVC tissues and 39% in bovine liver tissues using mosquito-inspired needles. To validate the developed bioinspired needle prototypes, a size scale study was performed using insertion test in a PVC tissue phantom. It was confirmed that the insertion force was decreased by 38% using different needle sizes. An analytical LuGre friction model was used to explain the insertion mechanics and to confirm the experimental results. Lastly, to investigate the effect of the insertion force reduction, the tissue deformation and the tissue damage studies were performed. Using a novel magnetic sensing system, it was observed that the tissue deformation caused by mosquito-inspired needles was decreased by 48%. A histological study was performed to quantify the tissue damage in bovine liver tissues. It was observed that the tissue damage of mosquito-inspired needles was reduced by 27% compared to standard needles. In conclusion, this dissertation study shows that applying bioinspired needle designs and vibration during insertion into tissues reduces the insertion force, the needle-tip deflection, the tissue deformation, and the tissue damage. The outcome of this study will benefit medical communities to advance the bioinspired needles for vibration-assisted clinical procedures. / Mechanical Engineering

This dissertation presents innovative research on Shape Memory Alloy (SMA)-actuated active steerable needles to address the limitations of conventional bevel tip needles in needle-based medical procedures such as biopsy, brachytherapy, tissue ablation and drug delivery. The active needle design proposed in this study surpasses the limitations of conventional needles by enabling large tip deflection and active control of deflection during needle insertion, thereby achieving accurate needle placement. A needle prototype was developed, demonstrating substantial 50mm and 39mm tip deflections at a 150mm insertion depth in liver and prostate-mimicking gels, respectively. Finite Element Analysis (FEA) accurately predicted the tip deflection in tissue-mimicking gels, with simulation errors measuring only 16.42% and 12.62% in the liver-mimicking gel and prostate-mimicking gel, respectively, validating the effectiveness of the FEA framework developed in this research for predicting tip deflection in soft tissues. Furthermore, a real-time trajectory tracking control system using a Proportional Integral (PI) controller was designed for the SMA-actuated needle, which resulted in minor root mean square errors (RMSE) of 1.42mm and 1.47mm in the two gels, respectively, highlighting the applicability of the needle design. The capabilities of the active needle, including improved tip deflection and trajectory tracking control, enable it to bypass obstacles, maneuver around critical anatomical structures, and increase the accuracy of needle placement, thus enhancing patient safety and procedure success rates.A bioinspired approach was introduced to enhance the functionality of SMA-actuated needles, drawing inspiration from the mosquito proboscis's unique design and skin-piercing technique. By incorporating an innovative cannula design and applying axial vibration to the SMA-actuated needle, a significant reduction in needle-tissue interaction friction was achieved, which resulted in increased needle tip deflection and improved steering accuracy. Including these bioinspired features led to a remarkable decrease in insertion force by up to 26.24% and an increase in tip deflection by 37.11%. Furthermore, the trajectory tracking error was reduced by 48%, and the control effort decreased by 23.25%, underscoring the benefits of the bioinspired enhancements in improving needle insertion mechanics and control. The findings presented in this dissertation illustrate the potential of SMA-actuated needles and bioinspired features in enhancing needle steering performance during minimally invasive needle-based procedures. Future research will focus on further refining the needle design and control systems, expanding experimental tests to biological tissues, and exploring the application of these advancements on a clinically applicable scale. / Mechanical Engineering

Background: Majority of cancer interventions today are performed percutaneously using needle-based procedures, i.e. through the skin and soft tissue. Needle insertion is known as one of the recent needle-based techniques that is used in several diagnostic and therapeutic medical procedures such as brachytherapy, thermal ablations and breast biopsy. The difficulty in most of these procedures is to attain a precise navigation through tissue reaching target locations. Insufficient accuracy using conventional surgical needles motivated researchers to provide actuation forces to the needle’s body for compensating the possible errors of surgeons/physicians. Therefore, active needles were proposed recently where actuation forces provided by shape memory alloys (SMAs) are utilized to assist the maneuverability and accuracy of surgical needles. This work also aims to introduce a novel needle insertion simulation to predict the deflection of a bevel tip needle inside the tissue. Development of a model to predict the behavior of the needle steering in the soft tissue has been always a point of interest as it could improve the performance of many percutaneous needle-based procedures. Methods: In this work first, the actuation capability of a single SMA wire was studied. The complex response of SMAs was investigated via a MATLAB implementation of the Brinson model and verified via experimental tests. The material characteristics of SMAs were simulated by defining multilinear elastic isothermal stress-strain curves. Rigorous experiments with SMA wires were performed to determine the material properties as well as to show the capability of the code to predict a stabilized SMA transformation behavior with sufficient accuracy. The isothermal stress-strain curves of SMAs were simulated and defined as a material model for the Finite Element Analysis of the active needle. In the second part of this work, a three-dimensional finite element (FE) model of the active steerable needle was developed to demonstrate the feasibility of using SMA wires as actuators to bend the surgical needle. In the FE model, birth and death method of defining boundary conditions, available in ANSYS, was used to achieve the pre-strain condition on SMA wire prior to actuation. This numerical model was validated with needle deflection experiments with developed prototypes of the active needle. The third part of this work describes the design optimization of the active using genetic algorithm aiming for its maximum flexibility. Design parameters influencing the steerability include the needle’s diameter, wire diameter, pre-strain, and its offset from the needle. A simplified model was developed to decrease the computation time in iterative analyses of the optimization algorithm. In the fourth part of this work a design of an active needling system was proposed where actuation forces of SMAs as well as shape memory polymers (SMPs) were incorporated. SMP elements provide two major additional advantages to the design: (i) recovery of the SMP’s plastic deformation by heating the element above its glass transition temperature, and (ii) achieving a higher needle deflection by having a softer stage of SMP at higher temperatures with less amount of actuation force. Finally, in the fifth and last part of this study, an Arbitrary-Lagrangian-Eulerian formulation in LS-DYNA software was used to model the solid-fluid interactions between the needle and tissue. A 150mm long needle was considered to bend within the tissue due to the interacting forces on its asymmetric bevel tip. Some additional assumptions were made to maintain a reasonable computational time, with no need of parallel processing, while having practical accuracies. Three experimental tests of needle steering in a soft phantom were performed to validate the simulation. Results: The finite element model of the active needle was first validated experimentally with developed prototypes. Several design parameters affecting the needle’s deflection such as the needle’s Young’s modulus, the SMA’s pre-strain and its offset from the neutral axis of the cannula were studied using the FE model. Then by the integration of the SMA characteristics with the automated optimization schemes an improved design of the active needle was obtained. Real-time experiments with different prototypes showed that the quickest response and the maximum deflection were achieved by the needle with two sections of actuation compared to a single section of actuation. Also the feasibility of providing actuation forces using both SMAs and SMPs for the surgical needle was demonstrated in this study. The needle insertion simulation was validated while observing less than 10% deviation between the estimated amount of needle deflection by the simulation and by the experiments. Using this model the effect of needle diameter and its bevel tip angle on the final shape of the needle was investigated. Conclusion: The numerical and experimental studies of this work showed that a highly maneuverable active needle can be made using the actuation of multiple SMA wires in series. To maneuver around the anatomical obstacles of the human body and reach the target location, thin sharp needles are recommended as they would create a smaller radius of curvature. The insertion model presented in this work is intended to be used as a base structure for path planning and training purposes for future studies. / Mechanical Engineering

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