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. ... Read more

Introduction: This research aims to develop a 3D-printed ergonomic handle design for a steerable laparoscopic instrument with minimised part assembly. Steerable laparoscopic instruments are used in minimally invasive surgery (MIS). MIS is a technique where surgeons insert long slender surgical instruments through small incisions of five to ten millimetres in the abdominal wall. According to various studies regarding the ergonomics of laparoscopic instruments, improvements in the control and handle design are necessary. Non-ergonomic design and control, combined with extensive surgery, can cause physical discomfort, muscle fatigue, mental stress, and other complications to the surgeon that can adversely affect the patient. Improvements in the design can overcome inconvenient and uncomfortable movements of laparoscopic instruments to make MIS safer for surgeons and patients. In addition to the improvements in ergonomics, a reduction in assembled parts in current laparoscopic instruments can shorten the assembly time, resulting in lower manufacturing costs. 3D-printing offers design freedom to enable complex structures with minimised part assembly and has the potential to customise the instrument specifically to the surgeon. Methods: The working principles and ergonomics of sixteen steerable laparoscopic instruments were analysed. Requirements were set up from the analysed laparoscopic instruments, handle design ergonomics and control ergonomics to develop an ergonomic handle design. Concepts have emerged from the requirements, and the most promising concept has been developed towards a final design. From the final proposed handle design emerged a working prototype, The LapaJoy. The 3D-printing technique of stereolithography was used to manufacture the LapaJoy. Steering, grasping, bending and locking tests were conducted to compare the retrieved data with the requirements to validate and evaluate the working principle and performance of the LapaJoy. Results: The LapaJoy consists of five assembled parts and allows the surgeon to control the four different functions of the instrument. The surgeon can control the end-effector in two degrees of freedom, lock the end-effector's position, open and close the grasping forceps, and lock the grasping forceps in place. All four functions of the LapaJoy can be performed by a novel two-finger control system using the index finger and thumb. The results show that the LapaJoy can manipulate the end-effector in two degrees of freedom by 20 degrees and lock the end-effector in any desired position. The instrument's grasper is functional, and the grasping forceps can be locked in place upon release of the grasper trigger. However, an analysation showed a reduction in the opening range of the grasping forceps with each opening and closing cycle. Furthermore, a material response wherein deformation of the steering segment's flexure occurred. The steering segment's flexure was deformed by 9.9 degrees after applying almost 1 N to the grasping forceps in the vertical direction. In addition, fatigue and failure of the grasper and joystick design occurred during extensive use and testing. Conclusion: By developing the 3D-printed ergonomic handle design with minimised part assembly, new knowledge was acquired in the possibilities of 3D-printing as a manufacturing technique for laparoscopic instruments. Future research is recommended to increase the steering angle and use more durable materials to create a more reliable product. The instrument's performance showed excellent potential in 3D printable laparoscopic instruments with minimised part assembly. The LapaJoy has the prospect of being an ergonomic, low cost, disposable MIS instrument. ... Read more

Objectives – Over the past decades, more and more cardiac diseases have been treated in interventional cardiology. Catheters are generally used to access the heart through the blood vessels. The previously developed steerable Sigma catheter at Delft University of Technology, tackles cable related challenges of conventional mechanically controlled catheters by an improved tip and shaft design. With its two finger-controlled joysticks, the handle allows full actuation of the four degrees of freedom catheter tip. However, this input control method is not specifically designed for optimal user experience. Therefore, the aim of this research is to design an input control method for the Sigma catheter tip and shaft design to improve task performance while reducing workload for the interventionist. Methods – A theoretical framework was composed and analysed to form design requirements. After detailing the functional and geometrical design, a functional prototype, the Epsilon catheter, was fabricated. To evaluate the proposed control method, an experimental setup was prepared and the control method of both catheters were compared. Six participants were asked to conduct the task, which consisted of contacting targets with the catheter end-point. Target-to-target times were measured and a self-report questionnaire was conducted. Results – The theoretical analysis was divided in the interventional environment, the interventionist who controls the catheter, and the instrumentation. A functional design was made, including catheter control through combining multiple fingers and the wrist using positive input-output coupling. The geometrical design achieved these functionalities through bending flexures and a 180° bended shaft. Data analysis of the experiment showed differences in target-to-target times and self-reported measures. Conclusion – The Epsilon prototype showed to fulfil on the requirements in a functionality test. The prototype allows steering the catheter tip in five degrees of freedom, single-handed in a handheld design. In the experimental setup, participants using the control method of the Epsilon catheter, performed the targeting task faster than using the Sigma catheter with reduced workload. Significance – Allowing the interventionist to control all manoeuvrability of the catheter tip single handed, may change the operational procedure during interventional cardiology. A single interventionist could perform extended treatment using two individually controlled multi-steerable catheters. Further developments will be towards design optimisations to further improve user experience and evaluation of the fifth degree of freedom. ... Read more

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. ... Read more

Introduction: When navigating through tight and delicate environments, steerable tools are highly desired. Follow-the-leader locomotion, as in the biological snake, is a solution that is obtained with shape memory control. The often used electric equipment to control the shape makes the current state-of-the-art of snake-like robots too complex. This thesis focused on a snake-like system using mechanical shape control to generate forward motion, to analyze the motion and comment on the expected behavior. Method: A 3D Simulink model was created with friction between the snake-like system and the surroundings as an important relation. A pre-defined sinus wave was passed through the snake-like system to analyze the motion. A low-cost, 3D printed, prototype was developed to validate the friction relation of the model. The prototype contains a belt feature with pre-defined path as shape control system and a snake-like system with four wheeled segments. Different configurations were assessed in the model by changing the wheel axis length, sinus amplitude and sinus frequency. Results: The prototype validated the realistic friction parameters in the model. Given the results of the model, the snake-like system creates forward motion by pushing against the surroundings when a sinus wave is pushed through the system. The wave parameters have a significant influence on displacement. When the configuration of the snake-like system creates more friction with the surroundings, the system is able to push itself further forward and generates more forward displacement. Conclusion:It is demonstrated that forward motion is possible when a snake-like system is connected to a mechanical shape control system. Now, the next step is to investigate random paths, to enable adaptable mechanical shape control being applied. ... Read more

In the field of prostheses, significant developments have been accomplished so far in low-cost prosthetic limbs using 3D printing technology. However, when it comes to prosthetic hands, 3D printed prosthetic hands are still limited in their grasping ability, such as the adaptability to the shape of an object and a sufficient pinch force level for practical use. The goal of this experimental study is to engineer a bio-inspired surface structure to improve the grip action of prosthetic hands. The low-cost FDM 3D printing technology in combination with the flexible material, Thermoplastic Polyurethane (TPU) 95A, was evaluated for this purpose. 3D printed surface (deformable) patterns were printed on top of a flat, rigid surface. The 3D printed patterns consisted of pillars or lines with varying thickness d, tip thickness D, wavelength λ, and curvatures α that were combined into different patterns. The frictional characteristics of the 3D printed patterns were assessed for nine different test scenarios, i.e. three different loads F_N against three different countersurfaces. Despite the small differences in the static coefficient of friction μ_s of the 3D printed patterns, some consistent trends were found. First, μ_s increases with increasing thickness d. Second, μ_s increases with increasing wavelength λ up to a point in which the decrease of number density of the 3D printed features decreases the overall friction. Third, μ_s increases for pattern curvatures with peaks in the opposite direction, such as wave or circular patterns. Lastly, μ_s decreases under increasing normal load F_N. The surface patterns were tested on the fingertips of a 3D printed prosthetic hand. The fingertips were assessed using the Box and Blocks Test (BBT), in which the pattern with the highest score displayed an ~70% increase in the number of blocks moved, compared to the original rigid fingertip of the 3D printed prosthetic hand in question. Further research and development are essential, especially for the FMD 3D print process of small dimensional printing in combination with flexible materials. Nevertheless, the proposed fingertip pattern demonstrated a first step towards future improvements of the grip action of low-budget 3D printed prosthetic hands using soft fingertip patterns.
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Access to prosthetics is very limited to many potential
users, while the need is high. There are two main reasons
for this that both are related to the production of prosthetics: the lack of skilled people and high costs. Minimized
assembly production using 3D printing could be a solution: no training is required, assembly takes only a short
amount of time and cheap materials can be used. Besides,
3D printing is a good method for customization. Therefore, this study proposes a 3D-printed finger for a bodypowered hand prosthesis with minimized assembly. The
design approach is the following. First, the human finger
anatomy is studied. Then, a stylized version of the human
finger is made that includes only the functions required for
the prosthesis. Finally, the design principles of the stylized
finger are evaluated and structurized. Based on the design
principles, a finger for a prosthetic hand is designed and
a prototype is developed. The prototype is produced with
an Ultimaker 3 using a rigid and a flexible material in one
print. The evaluation of the prototype shows promising
results. The finger is suitable for a hand prosthesis that
can perform an adaptive power grip and a pinch grip. The
mass of the finger is 17 grams, which makes the finger
comfortable to wear. An actuation force of only 16 N is
required to fully bend the finger. Minimized assembly and
cheap production are achieved: only four assembly steps
are required and the material costs are only 1.68 euros
per finger. In conclusion, the prototype shows a promising
step in the direction of a hand prosthesis that is affordable,
functional, body-powered, and has minimized assembly ... Read more

Background: Delft University of Technology has developed two working prototypes of flexible instruments for surgery, together with a master-slave system. The master-slave system is compatible with the simple parallel cable configuration and the more complex parallel and diagonal cable configuration. It is assumed that the instrument with a complex cable configuration requires fewer segments, compared to an instrument with a simple cable configuration, to cover a complex path, with the same accuracy.
Study design: research
Methods: The two different cable configurations are modeled. The model will first determine the shapes one segment can form. Afterwards, the possible shapes of the segments are combined to judge the performance of the flexible instruments with an algorithm. The algorithm is purely kinematic and does not take forces into account.
Results: The results show a strong preference for the cable configuration with parallel and diagonal cables. This configuration needs fewer degrees of freedom to reach the same error.
Conclusion: Therefore it can be concluded that the cable configuration with parallel and diagonal cables is more promising in combination with the predesigned master-slave system.
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