During a vitrectomy procedure vitreous is removed from the eye with a vitreous cutter, called a vitrectome. This instrument is comprised of two needles that move to cut the vitreous into small pieces before aspirating them. Vitreous cutters are complex instruments that are light and small in size to increase their accuracy. Because of their small size, and complexity, they are assembled by trained technicians with the help of a microscope. It is believed that new technologies such as additive manufacturing (AM) might be able to reduce the manufacturing complexity associated with vitreous cutters. The goal of this study was therefore; "To create a non-assembly driving mechanism for a vitreous cutter that is designed for AM". In order to achieve this goal, the functions of a vitreous cutter were identified, as well as the mechanisms that fulfil these functions in current instruments. Furthermore, the general limitations of AM were researched and listed. Extensive research was done to identify examples in the scientific literature to find linear actuators that were made by means of AM as an integrated assembly. A diaphragm actuator was selected to drive the mechanism based on the limitations of AM, the requirements, and examples found in the scientific literature. An in depth analysis of diaphragm driven vitreous cutters revealed that it would be a challenge to seal the air chamber of the instrument. A new concept was created that used one of the strengths of AM to solve this problem, by creating a compliant interface between the moving needle and the air chamber. A proof of principle prototype was created to quickly test if it would be possible to create movement by sealing the air chamber with differently sized diaphragms. Based on the concept of sealing an air chamber with flexible diaphragms, four concept variations were created.
It was decided to make a series of prototypes of one of these concept variations to study its performance. In total, 9 prototypes were manufactured using material jetting, out of Agilus30 and Vero, without the need of post-assembly. The prototypes were tested by applying a range of air pressure pulses, while measuring the force, the displacement, the actuation time, and the spring properties of the mechanism. With the successful manufacturing of the prototypes, it has been shown that it is possible to produce the novel driving mechanism using current AM techniques without any assembly steps other than the sealing of a cleaning hole to remove support material.  The tests revealed that the spring force of the mechanism was not linear for all materials, and that there was hysteresis present in the mechanism.  Furthermore, it was shown that none of the samples were capable of operating at the desired speed of 8000 pulses per minute (PPM). The soft samples were seen to have the best response time during the backward motion of the mechanism. A new driving mechanism was created in this study that utilized one of the strengths associated with AM. To the knowledge of the author this mechanism is the first of its kind, and has not been previously applied in another instrument. Additional knowledge on the material properties of digital materials is needed to be able to design a diaphragm mechanism that has the appropriate performance characteristics. With additional design efforts and research it could be possible to produce vitreous cutters using AM in a non-assembly manner. This could lead to a future where surgical instruments are manufactured on site and on demand.

The DragonFlex, world’s first 3D-printed steerable Minimally Invasive Surgery (MIS) instrument, showing promising results for the medical field, is made by means of 3D-printing, and features simple assembly, while exhibiting high bending stiffness. In this research, the possibilities with additive manufacturing are explored even further, by minimizing the number of parts and thereby reducing the assembly time. The objective of the study was to design a one-part instrument, based on the DragonFlex, having the same functionality as the DragonFlex, while only requiring the assembly of the control wires. This one-part instrument is called the MonoFlex. In an iterative process of designing in SolidWorks (2018) and testing printed samples, the design of the MonoFlex was developed until final prototypes were obtained, both with and without steering segments. Final compression and torsion tests showed that the grasping forceps side and the control handle side, broke when exposed to torsion moments of 32.9 Nmm and 20.8 Nmm respectively and compression forces of 0.2 N and 1.5 N respectively. When the instruments were exposed to tensile forces up to 19.6 N, both sides did not show any sign of failure. The maximum grasping force reached was 2.4 N, lower that the average grasping forces (of 10 – 20 N), required to grasp tissue. The printed parts were slightly different from the parts drawn in SolidWorks, this was because of the incomplete addition of support material, and the post-processing method. The working principle of a one-part 3D-printed grasping prototype was proven. A recommendation for future research is to make the MonoFlex stronger and more durable by using multiple materials. This will bring medical technology another step closer to fully non-assembly 3D-printable MIS instruments.

Flexible steerable needles can follow curved paths inside the human body, allowing to steer around objects, to adjust for mispunctures, and to reach multiple targets. However, the designs of existing ultra-thin (diameter < 1 mm) steerable needles require axial rotation of the needle to steer in 3D space causing needle twisting, which results in difficulties in needle trajectory control. Therefore, the goal of this paper is to design and experimentally evaluate an ultra-thin steerable needle, which can steer omnidirectional without the need of axial rotation.This study describes a new way of ultra-thin needle steering by a retractable steering mechanism inside a flexible cannula. The steering mechanism prototype consists of three Nitinol wires with a small custom-made curvature at the tip to increase the internal bending moment. Pulling one or multiple elements results in reorientation of the tip , thereby allowing to steer without axial rotation of the needle. An experimental prototype was made, which includes the needle together with a control unit. The final needle prototype has a total of three elements to steer in three-dimensional space and has an outer diameter of 0.5 mm.The prototype was tested in porcine gelatine phantoms (10 wt%) to evaluate the performance of the needle in terms of steering direction and curvature. The needle was able to steer towards the direction of the retracted element. Increasing the level of element retraction resulted in a higher steering curvature.The maximal median deflection was 62.76 mm for an insertion of 65 mm into the gelatine. The proposed needle showed good potential in omnidirectional steering with high curvature and it is able to follow multi-curved trajectories. Future improvements can be done to refine the design and make it user-friendly. Possibly, this will allow the proposed needle to compete with ultra-thin standard bevel-tip and pre-curved needles.

Engineers typically design heavy and powerful tools for the use of bulk transfer. High forces are needed to penetrate and to propagate into the bulk. Especially when using a grab, a reduction of mass is desirable. In the conventional approach an optimization problem is encountered as a further reduction in mass reduces the grabs ability to propagate into the bulk and fill itself effectively. To avoid this trade-off a different approach is required.
In nature, there are organisms capable of burrowing into substrates, such as mud or sand, without the use of high forces. The aim of this work is to find and evaluate a new digging mechanism for the use in a grab, using a bio-inspired approach. The new digging mechanism is evaluated in order to make weight reduction possible, while maintaining the digging properties of the grab. The most important parameters of the new principle are evaluated by a series of experiments. The results of the experiments look promising to apply in a grab. Several potential concepts are discussed.