All posts by Paul Breedveld

TU Delft – Accessible Prosthetics through 3D Printing and a Smartphone App

This research project is part of the Delft Global Initiative program: the portal and booster of Science and Technology for Global Development at TU Delft. Aim of the program is to contribute to sustainable solutions for global societal challenges, through problem-oriented interdisciplinary technical research in close cooperation with partners in the developing world, to meaningfully improve lives of people living in poverty.


Combining modern advances in smartphone technology with the seemingly unlimited possibilities of 3D-printing, in this project we aim to create easy access to prosthetics for amputees in Third World countries. We will develop an advanced, free IOS / Android app that scans the amputee with a smartphone camera and completely automates the complex prosthetic design process ending in design drawings for a 3D-printer that manufactures a well-fitting prostheses. In this project we will not only generate new, fundamental knowledge on automatic designing and manufacturing, we will also collaborate with a number of charity organizations to stimulate local initiatives in 3D printing and to optimize the prosthetic supply chain.

Photo: Example of 3D-printed prostheses from Mich Ebelings “Not Impossible Project” in Sudan.

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DragonFlex Micro – Towards the Limits of 3D-Printing

Developed in 2012-2015, thickness 5 mm, steering range: ±90º in all directions, complex components made by 3D-printing.

The DragonFlex has been developed in close-collaboration with Dr. Filip Jelinek, former PhD from the BITE-Group and currently employed at ACMIT.

In follow-up of the successful DragonFlex Macro, the DragonFlex Micro has been miniaturized to a 5 mm scale, where special attention has been given to the reliability and precision of the mechanism and optimization of the 3D-printing technique for such small scale components. Developing and optimising new design methodologies for 3D-printing,  a number of prototypes have been manufactured from different materials, resulting in world’s first steerable surgical instrument made entirely by 3D printing.



DragonFlex Macro – Smart Steering by 3D-Printing

Developed in 2010-2011, thickness 15 mm, steering range: ±90º in all directions, made entirely by 3D-printing.

Despite its success, e.g. in prostatectomy, da Vinci’s steerable grasper EndoWrist from Intuitive Surgical has a complex design prone to steel cable fatigue, potential sterilization issues and high associated costs, all of which insinuate a need for an alternative. The aim of our DragonFlex project is to demonstrate a design of a structurally simple handheld steerable laparoscopic grasping forceps free from cable fatigue, while attaining sufficient bending stiffness for surgery and improving on EndoWrist’s maneuverability and dimensions.

Having equal joint functionality to EndoWrist, DragonFlex’s instrument tip contains only four parts, driven and bound by two cables mechanically fixed in the handle. Two orthogonal planar joints feature an innovative rolling link mechanism allowing the cables to follow circular arc profiles of a diameter 1.5 times larger than the width of the instrument shaft. Besides maximizing the cable lifespan, the rolling link was designed to equalize the force requirements on both cables throughout joint rotation, making the handling fluid and effortless. The smart stacked joint design enables control of seven Degrees of Freedom (DOF) by only two cables and seven instrument components in tip, shaft and handgrip altogether.

The DragonFlex prototype was developed by means of 3D-printing, allowing grasping and omnidirectional steering over ±90°, exhibiting promisingly high bending stiffness and featuring extreme simplicity. DragonFlex concept sheds new light on the possibilities of additive manufacturing of surgical instruments, allowing for a feature-packed design, simple assembly, suitability for disposable use and potential MRI compatibility.



NWO – Multi-Steerable Cardiology Instruments – MULTI

This research project is part of the iMIT program and funded by the Netherlands Organization for Scientific Research NWO. The iMIT Program, executed by a community of Dutch Universities, university medical centers, and companies, aims to develop instruments for minimally invasive interventions. The program will result in the development of interactive Multi-Interventional Tools (iMIT)  that can adapt to their environment and integrate diagnostic and therapeutic functionalities, thus permitting effective single-procedure interventions.

Project MULTI – Design and development of multi-steerable tools for cardiac interventions

Cardiac Catheters  
The field of interventional cardiology is a growing branch of cardiology where minimally invasive instrumentation is of high importance. Catheters are among the most versatile and essential instruments used in interventional cardiology. Where in the past they were designed as flexible tubes, meant for monitoring or drug delivery, today catheters have evolved into more complicated and steerable instruments with additional tip functionality. As such, a large variety of commercially available catheters exist, being adopted in treatments of, for instance, heart rhythm defects and heart valve disease.

Current Difficulties
Despite their frequent and essential use, currently existing catheter designs have limited functionality as a result of several difficulties. Precise positioning of the catheter tip in the heart remains one of the biggest challenges as a result of complex 3D shapes inside heart and the absence of vessel wall support. In addition to that, respiration and heartbeat lead to a constant movement of the heart and changes in blood flow inside the cardiovascular system. Therefore, the use of catheters for complex interventions inside the heart requires a catheter tip that can be positioned accurately at the required location without damaging the heart or other surrounding anatomy. Of specific interest are cardiac biopsies and ablations, where mal-positioning of the catheter due to a lack of steerability can results in severe complications such as ventricular perforation or heart block. This research project at the TU Delft therefore focuses on designing and developing a catheter that is multi-steerable and is able to be directed towards and positioned inside any location in the beating heart.

Multi-Steerable Catheter
The aim of this project is to develop new and multi-steerable catheter technology based on the cable-ring technology and human factor experience at the TU Delft. First catheter concepts will allow left/right and forward/backward motion without rotation of the catheter shaft. More advanced concepts will be included with electro-mechanic controls and multiple steering segments that will allow for complex 3D tip motion. Finally, in-vitro evaluation on an isolated beating heart will take place to enable accurate positioning under physiological circumstances. The project is intended to result in explicitly evaluated multi-steerable catheter prototypes that are ready for commercialization. The realization of such a multi-steerable catheter will offer application in more complex minimally invasive cardiac interventions such as annuloplasty procedures, cardiac tissue resections, precision cardiac biopsies, septal defect closures, and valve implantations. Moreover, our focus is on development of steerable catheters for cardiac biopsies and ablations.

I-Flex – Steering Towards Miniaturization Limits

Developed in 2007-2008, diameter 0.9 mm, steering range: ±90º in all directions.

The retina is a light-sensitive layer at the inside of the eye. The macula is the region at the center of the retina with the highest concentration of light-sensitive cells. Macula degeneration – a disease which is a major cause of blindness –  is caused by a disfunctioning choroid layer under the macula. A way to treat macula degeneration is to perform surgery to the choroid layer via a tiny incision in the retina near the macula.  Reaching the choroid layer under the macula is extremely difficult as the surgeon has to operate through the incision under an angle while avoiding damage to the extremely delicate macula layer.  A steerable instrument could potentially solve this issue by making it easier to steer the instrument through the incision.

The largest design and fabrication challenge of such an instrument is the extreme miniaturization of the steerable mechanism in the tip. Down-scaling our patented Cable-Ring mechanism, already applied in the Endo-Periscope III and MicroFlex, to a very small scale, resulted in the  I-Flex – world’s smallest steerable surgical instrument that can be steered in all directions. The compliant tip has a diameter of only  0.9 mm and is constructed from 7 steel cables and a spring. Being equipped with a tiny gripper, the tip can be steered in two Degrees of Freedom (DOF). The instrument contains a novel handle that combines intuitive steering with a fine and precise pincer grip.

Feedback of experienced eye-surgeons from the Eye Hospital in Rotterdam has led to the development of a second prototype which is currently under construction. This instrument incorporates a different handle, allowing further miniaturization of the steerable tip to a diameter of only 0.45 mm – three times the size of a human hair.




MultiFlex – Tentacle from Steel



Developed in 2008-2009, diameter 5 mm, steering range: ±200º in all directions.

The MultiFlex is what we call a multi-steerable instrument. Based on the Cable-Ring mechanism applied in the Endo-Periscope III, the MultiFlex does not contain just one, but five steering segments serially stacked on top of each other. Each of these segments can be actuated in two Degrees of Freedom (DOF) by its own set of four steering cables, resulting in a total of 20 steering cables and a 10-DOF maneuverable tip capable of making a wide range of 3D shapes and curves. This level of maneuverability gives the instrument the ability to steer around anatomic strucures, making it world’s first instrument of this kind developed at 5 mm dimensions.

By using the Cable-Ring mechanism, all actuation cables could be positioned at the same diameter. Consequently, the increase in maneuverability does not affect the outer diameter of the instrument, which is still equal to Ø5 mm with a complexity similar to the Endo-Periscope III. The control handle of the MultiFlex has a  structure similar to the tip, yet its dimensions are scaled-up for a better fit to the surgeon’s hand.





Steerable Guidewire – Maneuvering without Twisting

Developed in 2007-2008, diameter 0.9 mm, length 1 m, steering range: ±90º in all directions.

The Steerable Guidewire has been developed by spin-off DEAM in a very close collaboration with the BITE-group, using our patented Cable-Ring technology. Intended for easy steering through a network of blood vessels during catheter interventions, the guidewire contains a flexible shaft ending in a steerable tip with two Degrees of Freedom (DOF). The mechanism is novel as compared to existing guidewire designs in that it requires no need for twisting the guidewire body for re-directing the tip, which results in a much more stable and fluent 3D steering motion. The tip-mechanism is similar to the I-Fex and composed out of seven steering cables surrounded by a spring. The handle contains two joysticks, one at the proximal handle side and one at the distal handle side, that can both be used to control the 2-DOF tip. The Steerable Guidewire forms the basis for a series of new multi-steerable catheters designs currently being developed in the BITE-group.




MicroFlex – Steering at a Micro-Scale

Developed in 2005-2006, diameter 1.3 mm, steering range: ±90º in all directions.

The MicroFlex is a steerable instrument for micro-surgery with a miniature Cable-Ring mechanism consisting of a ring of six steel cables (Ø0.2 mm) surrounded by a spring. The six cables are used for steering the tip, whereas the inner spring is replaced by a central cable that can be used to drive a miniature gripper on the tip (not yet incorporated in this prototype). The result is an instrument that realizes 3D-steering with only seven cables and a spring – smaller and at the same time simpler than existing steerable instruments.




Endo-Periscope III – Revolution from a Squid

Developed in 2003-2004, diameter 5 mm, steering range: ±110º in all directions.

Construction equivalent to Endo-Periscope II, however with Ring-Springs replaced by novel patented “Cable-Ring” mechanism based on tentacles of squid. The Cable-Ring mechanism consists of a ring of 22 steel cables (Ø0.45 mm) enclosed by two conventional coil springs, allowing only axial cable displacements to control the motion of the steerable tip. The Cable-Ring mechanism is entirely constructed out of standard parts and therefore very suitable for low cost mass production. The Cable-Ring mechanism is being commercialized worldwide by spin-off company DEAM.




Endo-Periscope II – Smart Ring-Spring Steering

Developed in 2001-2002, diameter 12 mm, steering range: ±125º in all directions.

The Endo-Periscope II has been developed in cooperation with Prof. Shigeo Hirose of the Hirose & Fukushima Laboratory, Tokyo Institute of Technology.

Endo-Periscope II is a simplified, patented version of Endo-Periscope I containing two enhanced compliant Ring Springs to control both left/right and up/down tip rotations. Endo-Periscope II contains an improved spatial parallelogram-mechanism that minimizes bending radius in all positions of the tip. A prominent part of the mechanism is a compression spring in the handgrip that compensates the spring force of the two Ring-Springs.