When treating a Chronic Total Occlusion (CTO) via Percutaneous Coronary Intervention (PCI), a guidewire first needs to be passed through or around the occlusion, a task requiring considerable skill and clinician experience. Proper backup support for the guidewire being used by the clinician is a prerequisite to prevent buckling or uncontrolled movement. Three different concepts that can vary their stiffness were generated, prototyped and evaluated against each other. Finally, a mechanism was designed that can vary its stiffness drastically by radially jamming wires together between a braided sheath and a radially rigid core that is also flexible in bending. Friction between the wires and the steerable segment generates the stiff configuration. If the braided sheath is released the wires can move along each other and the mechanism is flexible. The variable stiffness ability was tested by clamping the mechanism into a frame while applying a load to the distal tip. This resulted in a force-displacement curve that was 20 times stiffer in the stiff state than in the flexible state. The use of a braided sheath in a Variable Stiffness Mechanism (VSM) is an effective and simple way to obtain variable stiffness. The proposed design is a step forward in the developing process for VSM for cardiovascular applications.

In the history of medicine and surgery, a slow transition is made from open surgery to minimally invasive surgery. Nowadays, natural orifice transluminal endoscopic surgery (NOTES) is investigated and tested. A NOTES procedure includes flexible instruments, which are inserted through natural orifices such as the mouth, nose, anus or vagina. The instrument then passes transluminally towards the areas of interest. Benefits of this surgery method compared to conventional open surgery include, among others: the reduction in tissue trauma, no external scar tissue, less blood loss and a shorter recovery period. However, the method requires highly advanced medical devices that are slender and able to bend and form different paths to reach the area of interest. Bio-inspired by the movement and the propulsion of a snake, new instruments are being developed that provide a follow-the-leader motion (FTL-motion). In a follow-the-leader mechanism, the user steers the tip of the instrument. The position given to the tip is stored and passed on proximally from segment to segment. This thesis aims to improve the existing mechanically controlled FTL-mechanisms, in which the shaft is controlled with four-cable control. In this research, a cylindrical mechanical path-planning module is designed and manufactured: the Cryptex Programmable Memory Mechanism (CPMM). The cylindrical shape improves cable-control, as it can simultaneously steer one cable and its antagonist, and control the motion of a compliant shaft in one plane. Two prototypes were developed: a machined prototype and a 3D printed prototype. Both designs were manually tested in four phases: individual components and subassemblies; the key component solely; integrated design excluding the key component; completely integrated design. It is concluded that the design of the 3D printed prototype is limited by the accuracy of the parts and the material properties. The machined prototype shows promising results, as it can form diagonal and curved paths as an output. Even though the performance of the CPMM prototype leaves room for improvement, it validates that the proposed concept can provide the follow-the-leader motion.

Standard treatment methods for prostate cancer often result in side-effects because of damage to the surrounding tissue. Magnetic resonance imaging (MRI) guided focal laser ablation to treat prostate cancer reduces the risk of adverse effects by preserving noncancerous tissue. Prostate cancer diagnosis and focal laser ablation treatment both require the insertion of a needle for biopsy and optical fibre positioning. The insertion of needles in soft tissues causes tissue motion and deformation, resulting in tissue damage. In this study, we propose an MRI-ready actuation system for a needle that can be inserted into tissue with a zero external push force and without buckling. The zero external push force is achieved by moving parallel needle segments in a reciprocating manner. The actuation unit’s design inspired by the click-pen mechanism actuates the reciprocating motion of six parallel needle segments by solely a discrete manual translating actuation as its input. A prototype, called the Ovipositor MRI-Needle, was built using 3D printed parts and six 0.25-mm diameter Nitinol rods. Experimental validation of the Ovipositor MRI-Needle in ex vivo human prostate tissue inside a preclinical MRI scanner showed that the needle could advance in three out of five measurements through the tissue. The Ovipositor MRI-Needle is a step forward in the direction of developing a self-propelling needle for MRI-guided transperineal laser ablation to treat prostate cancer.

A future version of the DEMCON Needle Placement System (NPS) for use in the Magnetic Resonance Imaging (MRI) scanner requires accurate and small actuators that are MR (Magnetic Resonance) safe; actuators that can safely operate without interfering with the MR environment. The pneumatic stepper motor was chosen for actuation of the aiming segments of the future NPS. The pneumatic stepper motor can be made out of MR safe materials and its actuation principle is MR safe. MR safe, small size pneumatic stepper motors that produce high resolution motion however, do not exist. The goal of this thesis is to design and prototype such a pneumatic stepper motor and test its performance. An MR safe, high resolution pneumatic stepper motor was designed. This motor, called the PneuScape, was designed to fit in the orientation module of the NPS. The design of the PneuScape is based on an escapement mechanism. A torque is applied to move the output and the escapement anchor indexes this movement, creating a step. The PneuScape currently has the smallest designed step size st = 0.83º of any MR safe pneumatic stepper motor. A prototype of the Pneuscape was developed using rapid prototyping techniques and its performance was evaluated. The total prototype did not meet all design requirements, in particular the requirement of maximum positioning error. Torque application does not work reliably and results in the motor skipping steps, diminishing the motor's accuracy. The escapement mechanism however, shows promising results in its performance. Recommendations were given to improve the prototype. If the prototype is improved with aid of the recommendations, a future version of the PneuScape is expected to meet the design requirements. Finally, the work in this thesis has made science take a step towards high resolution MR safe actuation.

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: During minimally invasive procedures, tissue damage can be limited by using smaller incisions and by using naturally occurring body orifices to reach the intervention site. During these procedures the need can arise to transport tissue. Think of a biopsy or the removal of polyps. This calls for a tool that can transport tissue and is also flexible such that the tool can be introduced via natural occurring body orifices. Currently either suction based techniques or forceps are used for these procedures. However, both show suboptimal behaviour. Friction-based transport, which is based on the egg laying principle of parasitoid wasps, is not prone to these sub-optimal behaviour modes but is not yet used in flexible systems. Methods: A mechanical analysis was conducted to generate an overview of the challenges that arise in flexible friction-based transport. This resulted in a list of requirements based on which possible concept solutions were analysed. Themost promising design for a flexible friction-based transport mechanism has a flexible shaft that consists of a number of wire ropes in combination with ring magnets. This shaft was manufactured and validated by transporting gelatin tissue phantoms with different material properties with the shaft in straight and in a curved position. After validation of the flexible shaft, an ergonomic handle was designed resulting in the final prototype. This final prototype was also tested by transporting gelatin tissue phantoms. Results: From the results can be concluded that the flexible shaft is able to transport tissue phantoms with different material properties while in straight and curved (R=59mm) position. The final prototype is showed that continuous transport was possible from the tip of the flexible shaft to the end of the handle with the shaft in straight and in curved position. The position of the shaft (straight vs. curved) did not result in a significant difference in the transport rate. Discussion and Conclusion: It can be concluded that friction-based transport is possible in a flexible tool. The mean transport rate in straight position ( 2.3 § 0.29 mm/cycle) is comparable to the transport rate of a rigid friction-based transport mechanism with comparable dimensions. This new flexible friction-based transport mechanism shows great potential to be beneficial for a number of medical procedures.

The MLD massage is a key component of a lymphedema patient’s treatment. Currently, research is ongoing manifesting a transition from system care to self-care by designing robotic sleeves that are able to perform an effective and safe MLD massage enabling the patient to gain a sense of empowerment and ownership over their treatment and time. This research presents an innovative approach towards the MLD treatment by introducing an intermediate step: the bio-inspired design of the patient training education tool (PTET), a tool which aids the patient in performing the MLD massage safely and efficiently by themselves. The PTET is a pliable and slim sheet that easily adapts to the contours of the limb. Exerting manual pressure onto this sheet induces a colour change at a specific pressure threshold, giving the lymphedema patients a visual sign they have reached the required amount of pressure for this type of massage. The mechanism of colour change is inspired by the cephalopod’s dispersion and aggregation of its chromatophores. This study presents the design and validation of the working mechanism of a bio-inspired flexible colour-changing sheet, and first insights into the adaptability of the design variables and their relation to the threshold pressure, threshold indent and degree of colour change.

The human brain integrates tactile sensory information from the fingertips to efficiently manipulate objects. Sensory impairments due to neurological disorders, e.g. stroke, largely reduce hand dexterity and the ability to perform daily living activities. Several feedback augmentation techniques have been investigated for rehabilitative purposes with promising outcomes. However, they often require the use of unpractical, expensive, or complex devices. In this work we propose the delivery of vibrotactile feedback based on the Discrete Event-driven Sensory feedback Control (DESC)to promote motor learning in post stroke rehabilitation. For this purpose, we prototyped a novel wearable device, namely the DESC glove. It consisted of a soft glove instrumented with PolyVinylidene Fluoride (PVDF) sensors at the fingertips and eccentric-mass vibration actuators to be worn on the forearm. We proceeded with the characterization of the device, which resulted in promising outcomes. The DESC glove was tested with ten healthy participants subsequently in a pick and lift timed task. The effects of augmented vibrotactile feedback were assessed comparing it to a baseline, consisting of wearing the device unpowered. The results of this pilot study showed a decrease in the time necessary to perform the task, a reduction in the time delay from load force to grip force activation and a diminishing of the grip force applied on the object, which led to a lower breakage rate in the intervention condition. These promising outcomes encourage further experiments with stroke survivors to validate the effectiveness of the device to improve hand dexterity and promote stroke rehabilitation.

Steerable medical instruments are used to reach difficult locations in the body during minimally invasive surgery (MIS). Researching these instruments helps to further improve their performance and reduce their size making them even less invasive. However, developing new technology can be expensive and often complete custom test rigs are build for these instruments. This thesis presents the design, manufacturing and validation of an affordable, open-source prototype test setup for multi-segmented tendon-driven manipulators aimed at stimulating academic innovation of these manipulators. The prototype allows manipulators to be changed swiftly for other or iterated designs. Computer aided design (CAD) was used to create the design and a novel low-cost 3D printed force sensor comprising a permanent magnet and Hall effect sensor was proposed costing only €2.11. The prototype uses readily available off-the-shelf components and custom 3D printed parts that can be manufactured using hobby grade fused deposition modeling (FDM) printers. Despite the prototype working as intended, there are some tolerance issues in the actuation mechanism and viscoelastic behaviour in the printed force sensor that requires more research. However, the prototype setup already has the potential to be used for preliminary testing of tendon-actuated manipulators. Future work should focus on improving the 3D printed force sensor for enhanced performance and reliability. This work contributes to the progression in testing and validating tendon-driven manipulators.

Minimally invasive surgery (MIS) has several advantages over conventional surgery, including reduced damage to the body, less pain, lower infection risk, and faster recovery. However, MIS reduces the amount of space in which clinicians can operate within the body. This often forces them to work around delicate anatomical structures. A new type of instrument that can manoeuvre the body with snake-like movement, also called follow-the-leader (FTL) locomotion, could be a solution. A challenging design aspect of FTL instruments is to conserve the instrument’s shape accurately while the instrument propagates into or retracts from the body. This thesis presents a new device, called the Dullomatic, which can conserve 2D shapes and fits inside an instrument’s flexible shaft. The Dullomatic contains two adjacent mechanical shape memories which alternate between a flexible and rigid state, together forming a shaft. The device can be operated such that it conserves the shape and shifts the shape backwards as the device propagates forwards, or vice versa, to attain FTL locomotion. A prototype of this design was manufactured at a 2:1 scale containing 3 segments per shape memory. This prototype was evaluated by performing four FTL steps over a curved trajectory and measuring the position of the segments after each step. The results show that the device could be operated to accurately follow this path with FTL locomotion. Further research is required to enhance its user interface and investigate its potential for miniaturization. The Dullomatic forms an interesting addition in the field of FTL devices and might be able to aid in further reducing the invasiveness of surgery.

Developments in minimally invasive surgery such as natural orifice transluminal endoscopic surgery and single port laparoscopic surgery have pushed medical devices to be higher articulated and more dexterous. These surgery methods have proven to greatly decrease bleeding, scar tissue, hospital time, and cost. The procedures involve the navigation of flexible instruments through tortuous anatomical pathways. To reduce chances of tissue damage it is desired to reduce the interaction with anatomical structures during the trajectory. To realize this aspect a so-called Follow-the-Leader (FTL) motion has been adapted as a design feature for medical devices. This motion allows for the shaft of the instrument to conform to the shape taken by its end-effector without relying on anatomical reaction forces. One strategy to achieve FTL motion is the so-called alternating advancement where two shafts subsequently switch from flexible to stiff in order to conserve the configuration of the shaft. These devices have been shown to possess relatively many degrees of freedom for a small number of actuators which can greatly reduce the cost of the device. A state-of-the-art analysis has shown that, despite the kinetic advantages, there are no alternating FTL devices that use pneumatically actuated shape locks to constrain the flexibility of the shaft. In this work an alternating FLT medical device with pneumatically actuated shape locks was designed, produced, and tested. The device has a diameter of 40 mm and nine degrees of freedom. The total bending angle is 90 degrees with a bending radius of 85 mm. The device leaves room for improvement but does show that two concentric shafts can be shape locked pneumatically to perform an alternating FTL motion.

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.