All posts by Paul Breedveld

Wasp-Inspired Tissue Transportation Device

Developed in 2017-2018, diameter 6 mm. 

A wasp ovipositor is a needle-like structure composed out of three elements, called valves. A female wasp uses this structure to drill into wood or fruit and deposit eggs inside a living host. The propagation of eggs through the ovipositor is achieved by a smart push-pull mechanism, in which some valves are pushed while other valves are pulled, using surface- and direction-dependent friction with the egg to make it move forward. Inspired by the ovipositor of parasitoid wasps, we developed a novel tissue transportation device that can transport tissue samples at a precisely controlled speed without any risk of clogging.

The developed mechanism consists of an outer tube surrounding six semi-cylindrical blades that make a reciprocal forward/backward motion, driven by a miniature electric motor with a cam, similar to our Self-Propelling Ovipositor Device. Tissue samples are transported using a friction differential between the tissue and the blades, at a speed which is set by the surgeon. We tested the device with various tissue-mimicking gels as well as with compacted minced meat, using different motion sequences of the blades. In all cases the substance was transported reliably, showing that the ovipositor principle is well-suited for tissue transportation and a useful alternative to conventional aspiration (suction)-based devices that are prone to clogging.

The BBC made a nice animation showing the working principle of the device. In a new research project within Dutch Soft Robotics we are currently equipping the device with a flexible steering section to facilitate tissue transport from difficult-to-reach locations in the human body.

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MemoFlex 2 – Mechanical Cam-Following Snake

Developed in 2018-2020, diameter Ø8 mm

During complex surgical procedures such as in skull-base surgery, there is a need to reach difficult-to-reach locations via narrow anatomic corridors. Performing surgery along complex 3D pathways requires a snake-like instrument that memorizes the 3D shape of the followed pathway and shifts the shape backward as the instrument moves forward. This snake-like method of locomotion is called “follow-the-leader locomotion”, in which the head is the “leader” and the body follows the pathway of the head, see the following animations:

Follow-the-leader locomotion requires a segmented multi-steerable instrument as well as a memory in which the angles of the segments can be stored and shifted. In robotic approaches, the actuation occurs by a range of electric motors controlled by a computer. Although feasible, this will result in a very complex system requiring additional safety measures to ensure reliability during surgery.

In a desire to create a simpler system, we explored an alternative follow-the-leader approach by using a mechanical memoryFollowing our  HelicoFlex design, the MemoFlex II contains an Ø8 mm multi-steerable tip with 14 segments controlled by 56 steering cables in 28 Degrees of Freedom. The novel compliant frame of the tip is entirely non-assembly 3D printed out of one single part, creating an easy-to-make construction with a large range of snake-like motion possibilities.

The mechanical shape memory consists of four 3D printed plates (two for the horizontal plane and two for the vertical plane) containing curved grooves representing the required pathway of the tip. The four plates are mounted in a rotatable blue cylinder that is surrounded by a static exoskeleton. When the instrument is moved forward, the cylinder turns around, driven by a cam in the exoskeleton, and the curved grooves move along a set of ball bearings, each bearing connected to one of the steering cables, causing the tip to move along the shape of the curved grooves. The pre-programmed groove-shape can be derived preoperatively from CT or MRI-images.

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SIGMA Catheter – steering inside the Heart

Developed in 2016-2017, diameter Ø3 mm, lumen Ø1 mm

In recent years, steerable catheters have been developed to combat the effects of the dynamic cardiac environment. However, current solutions are bound to a number of limitations: (1) low torsion, (2) shaft shortening, (3) high unpredictable friction, and (4) coupled tip-shaft movements. These effects make it very hard to steer in tortuous blood vessel and inside the heart.

In order to tackle these limitations we developed a novel multi-steerable catheter prototype with four degrees of freedom. The tip has two steering segments that can be steered in all directions, controlled by two joysticks on the handle: one for the thumb and one for the index finger. The prototype features automatic lock of the steering angle once the joystick is released.

To solve the four limitations mentioned above we used eight miniature Bowden-cables inside of the flexible shaft for independent omnidirectional steering of each tip segment. As each segment can steer in all directions, twisting the shaft is not needy for directing the catheter tip, which solves the issue with low torsion (1). The issue with shaft shortening (2) is solved with the Bowden-cables which are axially incompressible. The Bowden cables generate very low predictable friction (3) and coupled tip-shaft movements (4) are absent as the Bowden-cables transfer the joystick motions directly to the tip without influencing the shaft.

The ability to steer inside the heart with a variety of complex shapes and curves opens great possibilities for complex catheter interventions. We evaluated our SIGMA catheter in a transparent 3D printed heart, based on MRI-images and created by the company Materialize, as well as ex-vivo in a beating porcine heart at the LifeTec Group. Both evaluations show very promising results and superior behaviour as compared to conventional steerable catheters.

Publications:

Ali A., Sakes A., Arkenbout E.A., Henselmans P., Starkenburg R. van, Szili-Torok T., Breedveld P. (2019). Catheter steering in interventional cardiology: mechanical analysis and novel solution. Proc. Inst. Mech. Eng. Part H: Journal of Engineering in Medicine, 12 p.

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https://www.materialise.com/en/blog/how-a-modular-testbed-helps-medical-device-developers

Self-Propelling Ovipositor Device

Developed in 2016 by MSc. student Perry Posthoorn

A wasp ovipositor is a needle-like structure composed out of three elements, called valves. A female wasp uses this structure to drill into wood or fruit and deposit eggs inside a living host. The propagation of the ovipositor through the substrate is achieved by a smart push-pull mechanism, in which one of the valves is pushed while the other two are pulled, using the surface-dependent friction properties with the soft substrate to move forward.

Inspired by the ovipositor of parasitoid wasps, we developed a novel self-propelling Ovipositor Device designed for locomotion through the large intestine (colon). The device contains a miniature electric motor connected to a cylindrical cam. Six sliders are placed around the cam and move forward and backward following the path defined by the cam. Designed for motion through soft environments, the working principle of the propulsion mechanism is that multiple stationary sliders create sufficient friction to allow for a single slider to shuffle forward. In each step, one slider moves forward whereas the others remain stationary relative to the environment, generating a smooth and continuous motion at approximately 1/6 of the speed of a moving slider. The ovipositor mechanism allows a simple and robost construction that can be easily miniaturised to very small dimensions, see our research on self-propelled ovipositor needles.

Experiments were carried out with various flexible 3D-printed structures attached to the outer surface of each slider to generate direction-dependent friction for further enhancement of grip. Tests in plastic tubes showed fast and fluent self-propelled motion. Locomotion in a colon was succesfully achieved with an improved 3D-printed outer surface in which the tangential spacing between the sliding structures was decreased so that the colonic wall does not flex between them. The improved prototype was able to self-propel ex-vivo through a porcine colon without any visual damage to the colonic wall.

(Featured image adapted from “Braconid Wasp Ovipositing” by Katja Schulz is licensed under CC BY 2.0.)

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Ovipositor Needle II – Self-Propelling & Steering through Tissue

Developed in 2016-2019, diameters ranging from 1.2 mm to 0.4 mm. 

A wasp ovipositor is a needle-like structure composed out of three elements, called valves. A female wasp uses this structure to drill into wood or fruit and deposit eggs inside a living host. The propagation of the ovipositor through the substrate is achieved by a smart push-pull mechanism, in which one of the valves is pushed while the other two are pulled, using the surface-dependent friction properties with the soft substrate to move forward. Inspired by the ovipositor of parasitoid wasps, we developed a series of self-propelled steerable Ovipositor Needles with ultrathin diameters ranging from 1.2 mm to 0.4 mm.

Our first Ovipositor Needle prototype consists of six super elastic Nickel Titanium (NiTi) wires concentrically arranged around a seventh NiTi wire. The seven wires are interconnected at the tip with a small flower-shaped ring (Ø 1.2 mm) manufactured for minimal resistance during propulsion. The ring has a central hole to which the central wire is glued, surrounded by six concentric holes through which the six other wires can slide back and forth. Each proximal end of the six movable wires is connected to a miniature stepper motor, in which a leadscrew-slider mechanism converts rotational motion into linear motion.

We performed a series of experiments in which the needle was inserted in tissue-mimicking gel phantoms. The wires were sequentially moved back and forth, resulting in the needle moving forward inside the phantom using the surface-dependent friction properties between the wires and the gel. Different sequences of wire actuation were used to achieve both straight, curved and S-shaped trajectories.

In our second Ovipositor Needle prototype we changed the shape of the interlocking ring from cylindrical to conical to investigate the effect of pre-curved wires. We found out that pre-curved wires facilitate steering, however, at the drawback of a slightly larger tip diameter due to the use of a conical flower-ring.

In a final series of Ovipositor Needle prototypes, the flower-shaped ring was replaced by an thin-walled shrinking tube, glued to one of the outer wires, ultimately resulting in ultrathin 0.4 mm needle diameters three times the size of a human hair. The prototypes were tested in multi-layered gel phantoms with varying stiffness properties and artificial membranes, representing different organs and tissues. In a final series of ex-vivo experiments the needles were evaluated with success in porcine liver, kidney and brain tissue.

This project, in which we developed world’s thinnest self-propelled-steerable needles, shows the strength of a novel bio-inspired approach leading to a new generation of needles that can be used to reach deep targets inside the body without a risk of buckling and with the possibility to correct the trajectory. Our needles were developed within the WASP project that focused on the development of steerable needles for localized therapeutic drug delivery or tissue sample removal (biopsy). In a follow-up project, funded by the Netherlands Organization for Scientific Research (NWO) we will develop the needles further towards clinical application in urological interventions under MRI.

(Picture at the top adapted from “Braconid Wasp Ovipositing” by Katja Schulz is licensed under CC BY 2.0.)

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Design of a Smart Surgical Knife

Lumpectomy is the preferred surgical treatment for women diagnosed with early-stage breast cancer. At this stage, the cancerous tissue only forms a small portion of the breast and during lumpectomy, the surgeon removes this portion of the breast along with some surrounded healthy tissue to assure the complete resection of the tumor and meanwhile satisfactory cosmetic outcomes. On the surgical side, the tumor and healthy breast tissue cannot always be clearly distinguished, making it difficult for the surgeon to determine where to dissect the tissue. Difficulty in detecting the border of the tumor in lumpectomy can result in incomplete tumor resection which only can be determined by histopathological investigation of the excised specimens after the surgery. In this case, the treatment of the patient may continue with a re-excision surgery or extra chemotherapy. Using an intraoperative margin assessment technique during lumpectomy could help the surgeon with detecting the border of the tumor and distinguish it from the breast’s healthy tissue. Among different type of techniques, diffused reflectance spectroscopy (DRS) has recently become known as a promising tumor detection technique and has been widely studied for its application in this field. Recently we studied the possibility of integrating an electrosurgical knife with a DRS system to provide the surgeon with real-time oncological guidance during the lumpectomy. To find the optimum design of the smart surgical knife we are looking for an enthusiastic MSc student who can come up with creative design ideas.

If you are interested in designing surgical instruments and preferably have a background in mechanical design, then you are the right person for this MSc project/assignment.  For more information please contact Sara Azizian Amiri, s.azizianamiri@tudelft.nl.

MemoFlex 1 – Mechanical Surgical Snake

Developed in 2016-2017, diameter Ø5 mm

During complex surgical procedures such as in skull-base surgery, there is a need to reach difficult-to-reach locations via narrow anatomic corridors. Performing surgery along complex 3D pathways requires a snake-like instrument that memorizes the 3D shape of the followed pathway and shifts the shape backward as the instrument moves forward. This snake-like method of locomotion is called “follow-the-leader locomotion”, in which the head is the “leader” and the body follows the pathway of the head, see the following animations:

Follow-the-leader locomotion requires a segmented multi-steerable instrument as well as a memory in which the angles of the segments can be stored and shifted. In robotic approaches, the actuation usually occurs by a range of electric motors controlled by a computer. Although feasible, this will result in a very complex system requiring additional safety measures to ensure reliability during surgery.

In a desire to create a simpler system, we explored an alternative follow-the-leader approach by using a mechanical memory. Following the design approach of our MultiFlex, the MemoFlex 1 contains a 12 cm long, Ø5 mm multi-steerable tip with 14 segments that can be controlled individually in 28 Degrees of Freedom. Using 56 steering cables, the tip is connected to a bendable handle. When the handle is bent in a certain shape, the shape is mirrored and replicated by the tip.

The shape memory is a pre-bent stainless steel rod that slides through the bendable handle, driven by a crank. As the rod slides through the handle, its shape is detected by a 3D-printed compliant helicoid insert that makes the handle follow the shape of the rod precisely. The mechanism replicates the handle-shape to the tip which will then maneuver along a curved pathway equivalent to the shape of the pre-bent rod. The shape of the pre-bent rod can be derived from CT or MRI-images.

Our novel copy-and-replication mechanism shows promising results. Yet, the prototype has a high mechanical complexity. We therefore continued this research with an improved prototype, the MemoFlex 2, which contains aan improved shape memory mechanism and a strongly simplified compliant 3D-printed tip.

Publications

Octopus-based Instrument used for first time in OR

The ‘mechanical octopus’, a steerable laparoscopic instrument used for minimally invasive surgery in the abdominal cavity, has been used for the first time in an operating room.

Surgeons at the Haags Medisch Centrum are positive about the benefits that the innovative technology in the LaproFlex gave them during a gynaecological operation. The technology behind the instrument was conceived by Paul Breedveld, professor of Medical Instruments & Bio-Inspired Technology. Jules Scheltes, who also obtained his PhD at TU Delft in the field of medical product development and who co-founded the Dutch company DEAM, has been working these past two years to market the product. Following an exciting period, he received CE certification earlier this summer for the LaproFlex and is producing and selling it in Europe.

Paul Breedveld
‘The LaproFlex is an example of research at a university finding its way into industry.’

Jules Scheltes
‘Co-founder Wimold Peters and I are especially proud that we have managed to pull this off with our team. Surgeons have indicated that the instrument is providing them with a better view of the organ they are operating on, and that they can access it from an optimal approach route and are not inconvenienced by intersecting instruments in their field of operation anymore. This is great news. This is exactly what we’ve been working towards.’

What makes this instrument special is that it has a flexible tip. This is made possible by an ingenious steering system based on the anatomy of an octopus’ tentacle, the so-called cable crane mechanism, which ensures that the scissors or grasper can be steered in every direction. Paul Breedveld and the researchers in his Bio-Inspired Technology Group (BITE) have further developed this technology, which has now been globally patented, into a large number of prototypes of steerable surgical instruments. DEAM is a spin-off company of the BITE group that develops steerable precision instruments for minimally invasive interventions. DEAM collaborates with a number of universities of technology and university medical centres. The LaproFlex is the first commercially available instrument using a cable crane mechanism and is considered to be a particularly affordable, disposable alternative for the extremely pricey Da Vinci operation robot.

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MemoSlide – Moving like a Mechanical Snake

Developed in 2016-2017, 13 cm wide, 20 cm long, and 10 cm high.

During complex surgical procedures such as in skull-base surgery, there is a need to reach difficult-to-reach locations via narrow anatomic corridors. Performing surgery along complex 3D pathways requires a snake-like instrument able that memorizes the 3D shape of the followed pathway and shifts the shape backward as the instrument moves forward. This snake-like method of locomotion is called “follow-the-leader locomotion”, in which the head is the “leader” and the body follows the pathway of the head, see the following animations:

Follow-the-leader locomotion requires a segmented multi-steerable instrument as well as a memory in which the angles of the segments can be stored and shifted. In robotic approaches, the actuation usually occurs locally, within the segments, by miniature electric motors controlled by a computer. This will, however, result in a device much too large for surgical applications. Alternatively, the actuators can be stored in a handle so that larger motors can be used in combination with steering cables that transfer the motion to the snake-like tip. Although feasible, using electric actuators controlled by a computer will result in a complex and expensive system requiring additional safety measures to ensure reliability during surgery.

In a desire to create a relatively low-cost follow-the-leader system that combines high safety with small dimensions, we explored an alternative follow-the-leader approach by using a mechanical memory inspired by the technology of mechanical calculators such as Charles Babbage’s Difference Engine.

MemoSlide features two mechanical memory registers: a static register (green in the design drawing below) and a moveable register (red) in which the angles of 11 tip segments can be stored, the angles represented by 11 small Ø3 mm ball-bearings that can slide sideways through slots in the brass top plate . The two registers are mutually coupled via a system of ball-bearings and cams underneath the brass top plate. Both registers can be locked and unlocked, and the moveable register can be shifted one segment forward or backward relative to the static register. The position of the first tip segment can be controlled by turning the blue steering wheel. Turning the crank around the steering wheel then results in  a sequence of locking, unlocking and shifting motions, controlled by the four brass cams  at the corners of the device, to memorize and shift the position of the ball bearings backward along the registers. The movie below shows an example in which MemoSlide is programmed with a sinusoidal shape that is shifted backward along the device (and then forward again, as the device works in two directions).

Although in principle suited for controlling the shape of a snake-like surgical device, MemoSlide is in its current configuration still too complex and limited to 2D pathways. Based on our experience with MemoSlide, we are currently developing a new mechanical system suited for memorizing 3D shapes and sufficiently simple for integration in the handle of a snake-like  surgical device. We will keep you posted!

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