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

 

Ovipositor Needle I – Self-Propelling through Tissue

Developed in 2014, thickness 2 mm.

Wasp ovipositors  are thin and flexible needle-like structures used for laying eggs inside wood or larvae.  Wasp ovipositors are composed out of  longitudinal segments, called “valves”, that can be actuated individually and independently of each other with musculature located in the abdomen of the insect. In this way the wasp can steer the ovipositor along curved trajectories inside different substrates without a need for rotatory motion or axial push.

Inspired by the anatomy of wasp ovipositors, we developed an Ovipositor Needle containing a 2 mm thick “needle” composed out of four sharp and polished stainless steel rods, representing four ovipositor valves. The four valves can be individually moved forward and backward by means of  electromechanical actuators mounted in a propulsion unit that is standing on four passive wheels. If the needle is inserted into a gel that represents tissue, and if the four valves are sequentially moved forward and backward, the friction behaviour around the valves in the gel will result in a net pulling motion that drives the needle forward through the gel. The ovipositor needle is therefore self-propelling, meaning that it does not need a net pushing motion for moving forward through tissue like normal needles do.

Ovipositor Needle I is part of the  WASP project that focuses on the development of steerable needles for localized therapeutic drug delivery or tissue sample removal (biopsy). In a new prototype that is currently under development, we aim to extend the self-propelled needle with steering capabilities at an outer diameter of just 1 mm.

 

Publications