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 ENT or skull-base surgery, there is a need to approach difficult-to-reach locations via narrow anatomic pathways. Performing surgery along complex 3D pathways requires a snake-like instrument able to memorize the 3D shape of the followed pathway and shifting the shape backward as the instrument moves forward with its head steering in a new direction. 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 such as our MulfiFlex as well as a memory in which the angles of the segments can be stored and shifted to the neighbouring segments as the instrument moves forward. In robotic follow-the-leader approaches, the actuation usually occurs locally, within the segments, by miniature electric motors controlled by a computer that memorizes the shape. This approach will, however, result in a device too large for surgical applications with a maximum instrument diameter of Ø5 mm. Instead, the actuators can be stored in a handle or console placed outside the patient, so that larger motors can be used in combination with cables or rods 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!

Publications:

Henselmans P.W.J., Gottenbos S., Smit G., Breedveld P. (2017). The MemoSlide: an explorative study into a novel mechanical follow-the-leader mechanism. Proc. of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine. Vol. 23, No. 12, pp. 1213-1223.

Media:

http://www.npo.nl/de-kennis-van-nu/27-10-2016/VPWON_1263063

Accura: 8DOF Accurately Steerable Platform

As of today, Chronic Total Occlusions (CTO) represent the most technically challenging lesions interventionists face during Percutaneous Coronary Interventions (PCI), with considerably lower success rates (50-90%) in comparison to semi-occluded and acutely occluded arteries [1]. The main technical challenge in PCI of CTOs lies in successfully puncturing and crossing the CTO with a guidewire.

In this section we will focus on crossing challenges. For solutions to puncture the CTO, see the Pulze Hammer I, Pulze Hammer II (coming soon), Cradle Catheter (coming soon), and Wave Catheter (coming soon).

Crossing is challenging as the guidewire cannot be actively steered and deflection can thus not be compensated. This can lead, amongst others, to dissection of the blood vessel wall or subintimal crossing, in which the guidewire crosses the CTO via the blood vessel wall (between the intima and adventitia). Furthermore, it is often challenging to navigate through tortuous CTOs.

A steerable crossing device could be the solution to current crossing challenges, as it will give the interventionist the freedom to actively navigate through the vascular system and CTO freely. Therefore, a steerable prototype nicknamed the Accura was designed with an 8 Degrees Of Freedom (DOF) cable actuated tip (Ø 2 mm, L = 32 mm) divided over 4 steering segments; allowing for constructing complex S-curves. The tip contains a lumen (Ø 1 mm) to allow for the insertion of, amongst others, a balloon catheter, a guidewire, or an IntraVascular UltraSound probe (for visualization purposes). The steerable tip is connected to a rigid shaft (Ø 2 mm, L = 200 mm), which in turn is connected to the handle. The handle consists of an innovative combined locking and steering mechanism to lock the tip position in place and to precisely steer each segment separately. This construction allows for both the tip position and direction to be changed independently, allowing for a scanning movement.

The multisteerable tip has been successfully combined with a single element forward-looking IVUS transducer and Optical Shape Sensing (OSS) fiber to reconstruct a wire frame in front of the tip. This combination will allow for reconstructing and scanning a 3D volume in front of the tip, which can be used to determine the most suitable entry location. Furthermore, the addition of the OSS fiber can potentially minimize the use of X-Ray and contrast fluid during the intervention.

Even though it is still a long way towards a fully applicable clinical tool, the tests have given first insights into the possibilities and advantages of having such a tool in PCI. Currently, a multisteerable catheter is under development.

Publications:

  • Sakes A., Ali A., Janjic, J., and Breedveld P. (2018). Novel Miniature Tip Design for Enhancing Dexterity in Minimally Invasive Surgery. Journal of Medical Devices. Accepted.

Accura_device2

Volt – 3D-Printed Bipolar Laparoscopic Grasper

Developed in 2016, thickness 5 mm, complex components made by 3D-printing.

Controlling blood loss is a major challenge during laparoscopic surgery. In an effort to control blood loss, electrosurgical tools are often used. In current electrosurgical instruments, a high frequency electrical sinusoidal wave is passed through the patient’s body from an active electrode to a return electrode to minimize bleeding. Depending on the exact configuration of the electrosurgical instrument, it can be used to coagulate, cut, or destroy the tissue.

Even though current bipolar electrosurgical instruments have proven effective in minimizing blood loss, advancement is needed to improve the dexterity and adaptability of these instruments. With current advances in 3D-print processes and its integration in the medical field it has become possible to manufacture patient- and operation-specific instruments. Furthermore, by combining 3D-print technology with smart joint designs, the dexterity of the instruments can be significantly improved.

In order to overcome these challenges, we have developed the first 3D-printed steerable bipolar grasper (5 mm), named Volt, for use in laparoscopy. This 3D-printed design allows for easy adjusting of the geometry of the shaft and tip based on the patient’s anatomy and operation requirements. The grasper significantly improves dexterity by the addition of two planar joints allowing for ±65° for sideways and ±85° for up- and downwards movement. Furthermore, due to smart joint design, high bending stiffness of  4.0 N/mm for joint 1 and 4.4 N/mm for joint 2 is achieved, which is significantly higher than that of currently available steerable instruments. The tip consists of two 3D-printed titanium movable jaws that can be opened and closed with angles up to 170° and allows for grasping and coagulating of tissues. In order to actuate the joint, tip, and electrosurgical system, as well as to tension the steering cables, a ring handle was designed similarly in design to the one of Dragonflex.

In a proof-of-principle experiment, Volt was connected to a electrosurgical unit (Erbe) and was able to successfully coagulate fresh pig liver. Tissue temperatures of over 75 °C were achieved with an activation time of ~5 s.

Publications:

 

 

 

Virtual Prototyping

BRN Dutch News Radio
Programme: Eyeopeners
Presenter: Meindert Schut

 

Ewout Arkenbout, BITE-alumnus, was interviewed by BNR Dutch News Radio about his PhD-research on multi-branched surgical instrumentation, explaining his new “hands-off” design methodology to gain insight in intuitive interfaces for manual steering without constructing prototypes in hardware.

Listen to the interview (in Dutch) via the following link:

Assignment: Design, fabrication and evaluation of  an adhesion-based medical gripping instrument

Tissue manipulation during surgery is currently done with a grasping forceps. This pinching instrument is prone to errors related to the force that is applied on the gripped tissue. Using too much force may lead to tissue damage, whereas applying too little force may result in tissue slipping out of the forceps.

One way to realize firm yet gentle grip could be by means of an instrument that relies on adhesive forces rather than pinching forces. In this line, we are developing adhesive pads that can generate high friction forces on soft substrates, such as biological tissue.

In this research project you will be designing a medical instrument that integrates such an adhesive pad for tissue manipulation. One of the challenges herein is that such pads are optimized for high friction, which means that the range and type of movements for tissue manipulation may differ from these of a conventional gripper.

You will work towards the design and experimental evaluation of a prototype of an adhesion-based gripping medical instrument. This includes evaluation of the functional requirements of an adhesion-based instrument to be used in minimal invasive surgery, design and fabrication of a prototype thereof, and testing of its performance with phantoms and ex vivo.

Contact: Peter van Assenbergh, s.p.vanassenbergh@tudelft.nl

Pressure Wave Catheter for Coronary Interventions

This research project is funded by the Netherlands Organization for Scientific Research NWO.

Crossing heavily calcified occlusions, such as Chronic Total Occlusions (CTOs), is challenging, resulting in undesirably low success rates between 50% and 90% depending on the operator’s experience and the characteristics of the CTO. The most common failure mode observed in the preferred treatment, the Percutaneous Coronary Intervention (PCI), is the inability to cross the occlusion due to buckling of the guidewire. The inability to cross the CTO often leads to procedural failure and can cause damage to the blood vessel wall.

In order to prevent buckling of the crossing tool and improve the procedural success rates of PCI, we developed a novel, well-working catheter prototype that can apply a mechanical impulse, defined as the integral of a peak force over a small time interval, on the CTO during the crossing procedure. Using an impulse to dynamically load the CTO  is advantageous as the impulse strongly decreases the buckling effect and the static forces on the CTO and its environment, minimizing the risk of damage to the blood vessel wall and the surrounding tissues.

During this TTW demonstrator project we will develop our patented catheter prototype further into a  handheld clinical prototype incorporating an  adjustable tip section as well as a dedicated input mechanism allowing for generating a single impulse as well as continuously vibrating motions. The efficiency and effectiveness of the clinical prototype will be evaluated on CTO models and during ex-vivo and in-vivo animal evaluations.

 

Ovipositor Needle II – Self-Propelling & Steering through Tissue

Developed in 2016, diameter 1.2 mm (tip) & 0.75 mm (body).

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 push-pull mechanism, in which one of the valves is pushed while the other two are pulled.

Inspired by the ovipositor of parasitoid wasps, we developed a new Ovipositor Needle with a diameter of 1.2 mm at the tip and 0.75 mm along the body. The needle consists of six superelastic Nickel Titanium (NiTi) wires (Ø 0.25 mm, length 160 mm) concentrically arranged around a seventh NiTi wire. The seven wires are interconnected at the tip with a flower-shaped ring (Ø 1.2 mm, length 2.0 mm), manufactured for minimal resistance during propulsion. The ring has a central hole to which the central wire is glued and six holes through which the six other wires can slide back and forth.

Each proximal end of the six movable wires is connected to a stepper motor, in which a leadscrew-slider mechanism converts rotational motion into linear motion. During an experiment, the needle was inserted in a stationary tissue-mimicking phantom, placed on a cart with low-friction wheels. The wires were sequentially moved back and forth inside the phantom, generating a net pulling motion of the phantom towards the actuation unit, and resulting in the needle moving forward inside the phantom. Different sequences of wire actuation were used to achieve both straight, curved and S-shaped trajectories.

In a follow-up 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.

Ovipoistor Needle II is, to our knowledge, world’s thinnest self-propelled-steerable needle. Our novel bio-inspired steering and propulsion mechanism allows for the design of extremely long and thin 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.

Ovipositor Needle II is part of the WASP project that focuses on the development of steerable needles for localized therapeutic drug delivery or tissue sample removal (biopsy). We are currently  working on further miniaturization to diameters <0.5 mm.

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

Publications:

Novel Shooting Mechanism for Tissue Puncturing

In nature multiple animals have developed intriguing shooting mechanisms for food capture, defence, and reproductive reasons. Think for example on the amazing tongue shooting capability of the chameleon and the appendage strike of the mantis shrimp.

For a full overview of innovative and interesting shooting mechanisms in nature, we would like to refer to: Shooting Mechanisms in Nature: A Systematic Review by Sakes et al. [2016]

These shooting mechanisms can offer inspiration for new ideas on the technological development of fast acceleration mechanisms in medicine. High-speed shooting mechanisms can, for example, be used for the endovascular treatment of Chronic Total occlusions (CTOs). CTOs are heavily calcified and are thus difficult to puncture and cross with the small (0.36 mm) guidewire. The required force to puncture the CTO is often higher than the buckling force of the guidewire due to the low bending stiffness (EI) and long (unsupported) length (L). As a result, the guidewire often buckles. Buckling in turn causes procedural failure since the CTO cannot be crossed. Buckling of the crossing tool may be prevented by using a high-speed crossing tools as this increases the buckling resistance of the guidewire and potentially minimizes the puncture force of the CTO.

With this in mind an innovative high-speed crossing tool was developed using nature’s shooting mechanisms as inspiration. The crossing tool (OD 2 mm) incorporates an innovative spring-driven indenter and decoupling mechanism for high-speed puncturing of the proximal cap. First tests have been very promising. The prototype hit the CTO with an average speed of 3.4 m/s and was able to deliver a maximum force of 20 N (without buckling), which is well over the required 1.5 N to puncture the CTO. Additionally, the device was tested on CTO models made out of calcium and gelatine of different consistency. Puncture was achieved with on average 2.5 strikes for heavily calcified (77 wt% calcium) CTO models.

We feel that with continued development of this technique it will become possible to deliver high forces in ultra thin devices, such as guidewires, and as such increase the success rate of the the endovascular treatment of CTOs and other minimal invasive applications.

For a video of the prototype hitting a fixed surface, please see: Velocity_Max_10fps (Converted), which is slowed down 1000x.

Interventional Ductoscopy – the EVAPORATE study

This research project is funded by the Netherlands Organization for Scientific Research NWO and the Dutch Foundation of Cancer Research KWF.

Ductoscopy is a minimally invasive micro-endoscopic technique that allows for direct visualization of the milk ducts of the breast through their natural orifices in the nipple. It can be performed under local anesthesia in daily outpatient routine and has proven to be safe with a very low risk on (mild) complications. In collaboration with the UMC Utrecht, the aim of this project is to develop novel instruments for ductoscopy to prevent women from getting breast cancer.

3D Printed Hand: FA3D

The FA3D hand is a 3D printed Hand printed with a flexible filament. The fingers of the hand have multiple joints, allowing for adaptive gripping. The fingers have elastic joints and can be printed as one part. Therefore assembly of the finger phalanxes is not necessary.

FA3D Hand
FA3D Hand

Due to its adaptive gripping, the FA3D Hand can hold a broad range of objects.

FA3D Hand holding paper cup

The FA3D Hand consists of 8 3D-printed parts. The parts can be  connected with standard bolts and nuts. Steel cables are used to actuate the fingers.

Parts of the FA3D Hand
Parts of the FA3D Hand

The hand is body powered. It can be controlled by pulling the control cable, by using a shoulder strap.

User wearing the FA3D Hand
User wearing the FA3D Hand