Background: Accessing targets through complex trajectories with multiple curves in series, remains challenging today in many application fields, like surgery, the Fukushima disaster, maintenance of complex tube networks, mining and space operations. Current steerable devices require control of an extensive amount of segments, while moving as a whole through the environment. In contrast, growth-from-the-tip devices move only at the tip by creating a solidified support structure, allowing for active curvature creation at any point of the trajectory with limited effect on the environment. However, reversible and accurate growth remain challenging for these type of devices.Method: Competitive design requirements are setup and quantified. Subsequently, a broad concept generation is performed, based on the ACRREX (i.e. Abstracting, Categorizing, Reflecting, Reformulating and Extending ) method. After selection of one working principle, a proof-of-principle is designed, prototyped and evaluated. Based on the outcome, a second prototype is created and evaluated again. Evaluation of both prototypes comprise accuracy measurements, based on the ratio of path deviation from a kinematic model and insertion length. Moreover, load bearing capacity of the support structure, forces acting on the environment and overall performance are assessed.Results: The selected concept is based on everting chains, driven by torque at the tip and consisting of two chains with lockable sliding hinged joints. Both prototypes successfully show reversible and steerable growth-from-the-tip, by the fact that counter rotation of the tip gears resulted in a translation of the tip, while differential rotation of the gears resulted in curvature creation. Prototype I (PI) had an accuracy of 4.5% for pure translations and 6.2% to 8.1% for the formation of two sequential (90 degrees) curvatures. Prototype II (PII), which was not fully operational, had a deviation per insertion length of 2.9% for a single curvature and to 10.7% to 19.1% for a combination of translations and curvatures in series. Even though the shape-locks of Prototype I had 3 degrees play per joint and a limiting amount of locking positions, the average orthogonal load bearing capacity was high (49N) with an accompanied deformation of maximally 8 degrees. In contrast, the friction-locked drum brakes of Prototype II rotated up to 70 degrees, by both deformation (22%) and slippage (78%) at a load of 20N. A rotation of 25 degrees was reached at an average load of 7.3N. Normal forces acting on the environment during movement were only measured for Prototype I, resulting in direct distortions (78%) of <4N and indirect distortions (22%) of <0.36N. Moreover, both prototypes had comparable elongation rates (PI: 92.9mm/min, PII: 156mm/min), extension rates (PI: 2.6mm/mm, PII: 0.9mm/mm) and widths (PI: 268mm, PII: 270mm). Lastly, a minimal inner curvature of zero and a minimal outer curvature equal to the device’s width were realized, due to the presence of sliding hinged joints.Conclusion and discussion: Both prototypes performed reversible growth-from-the-tip based on the everting chains principle. Accordingly, the generated kinematic model that links gear rotations to tip rotations and translations seems to be an accurate simplification of the experimental data.In addition, the normal forces acting on the environment were much lower than the load bearing capacity of Prototype I, confirming sufficient support and limited deflection and deformation by the built structure. The everting chain principle has many advantages. First, multiple curves in series can be formed in a reversible manner. Moreover, high load bearing capacity of locked chains results in high accuracy of the system’s movement. Furthermore, the system has limited interaction with the environment and no additional system is required to create curvature. Lastly, sliding hinged joints allow for movement along sharp edges. The next generation of everting chain robots should incorporate improved power and load tuning, size reduction and chains that allow for fully selfsupporting movements in 3D space.

Background: Currently colonoscopies are difficult procedures to complete without complications. Due to the limitations in the state of the art flexible colonoscopes specialized maneuvers are required in order to allow the colonoscope to travel into the colon and reduce colon stretching. This thesis proposes a novel self-propelling mechanism designed to enhance the current flexible colonoscopes allowing for a better completion rate and fewer complications in colonoscopies. Methods: First an analysis was made of the fundamental types of propulsion and how well they could be used for locomotion inside the human colon. In order to determine the conditions the design has to meet a list of requirements was made. A wide variety of concepts were considered, which were then reduced to the three most promising concepts. These concepts were further developed and out of these, the most promising design was chosen. This design was adjusted in order to create a proof-of-principle prototype which was used to validate the design and give new insights into the type of self-propulsion used. Results: The prototype is able to perform locomotion in all tested tube/instrument diameter combinations, including tubes with a significant larger diameter than the instrument. Furthermore, the prototype is also able to perform well in tubes with an irregular shape and with a conical shape, both with and without lubrication. The effect of added weight to the tubes was also investigated and showed no significant effect. The efficiency of the prototype, as determined by the slip ratio, showed no significant variation during these tests. Discussion and Conclusion: The proof-of-principle experiments demonstrated that the design is capable of performing locomotion in the tested scenarios with better than expected efficiency. The lack of significant variation of slip ratio in tubes with a larger diameter than the prototype itself were unexpected and could significantly change the design of future iterations of the instrument. The issues which came up during the experiment gave new insights into the working of this type of locomotion which were used to make recommendations for future iterations of the design and recommendations for further tests, which could be performed to investigate unexplained results. The current design meets all the requirements set out for it and gave valuable new insights which will be useful for future iterations of the design making it a good first step towards developing a better colonoscope.

Retinal detachment occurs when liquid slips behind the retina and does not allow the latter to lay flat on the posterior region of the eye. It alters the vision of the patient, hence requiring surgery to be corrected. In some cases, retinal detachment can occur after the retina has been treated for other pathologies. Indeed, more than 20% of highly myopic patients who have been treated for retinal diseases are subject to retinal detachment a few months after the surgery and are required to undergo a second surgery. It is believed that a membrane, also called Vitreous Cortex Remnants (VCR), that arises due to vitreoschisis, a retinal disease, is the reason for the re-detachment. VCR is often not dealt with during surgery because its removal is time-costly, the VCR is not well visible and instruments are not optimally adapted for removing VCR. The work aims to develop and experimentally evaluate new methods of removing VCR. For that purpose, a series of test prototypes were manufactured, and three surgeons assessed the efficiency of the prototypes for removing VCR from dissected pig’s eyes. Each eye was treated pre-experimentally according to a new model that tries to recreate vitreoschisis in a young porcine eye. The efficiency of each test prototype was assessed based on the force that the instrument tip exerted on the pig’s retina, the number of strokes taken to remove the VCR completely, the tissue damage and the time used. Furthermore, the optimal tip length was determined based on the surgeons’ feedback. The results show that the force greatly depended on the stiffness of the instrument tip and that the most efficient prototype consisted of a PVA wipe cut to size 6x1x1 mm and a 0.1 mm diameter Nitinol wire. The prototype exerted a maximum force of 0.68 gr. The number of strokes was around 40, and the optimal tip length was just under 4.5 mm. While the experiments showed that it is a promising design, the tip needs to be remodeled to comply with the low stiffness needed and to be able to fit within a 23 gauge tube.