4TU – Soft Robotics

This programme is a collaboration of the four technical universities of the Netherlands (4TU): Eindhoven University of Technology, University of Twente, Wageningen University, and Delft University of Technology.

Conventional robots operate in pre-programmed environments, enabling the execution of repetitive tasks at superhuman speed and accuracy, based on a design of interlinked rigid segments that are position controlled. A radically different approach is required to enable robots to safely interact with organic matter (which is inherently vulnerable and unpredictable) or to operate in human-inhabited environments. Robots should be soft and compliant, but designing, manufacturing, modelling and controlling them brings many scientific and technological challenges. These challenges have recently begun to be addressed in the emerging research community of ‘soft robotics’.

Our soft robotics programme aims to establish a leading soft robotics community in the Netherlands, that will establish an integrated design approach for soft robotic hardware, control and actuation, inspired by nature. Unlike conventional robots, humans and animals are soft and flexible, and adaptive. While in conventional robots components such as motors, sensors, beams and computer are stacked, in animals functionalities such sensing, control, and actuation are fully integrated, distributed, and robust (i.e., failure of parts does not lead to a non-functional system). In biology the nervous system is distributed over the entire body, and the ‘design’ of the biomechanical motion systems reduces the control demands for the nervous system. For this reason, we want to unravel the solutions found in nature, and use them as inspiration for the design of Soft Robots.

Novel non-assembly 3D printed structures will be explored to integrate electronics and embedded micro-actuators. Additionally, we will investigate bio-inspired power cable structures that can withstand extreme stretch due to their shape. In close collaboration with Wageningen University, we will combine bio-to-techno transfer with techno-to-bio transfer, whereby knowledge of biological functionality is gained from building soft robotic devices.

For more information about this project, please contact Aimée Sakes, a.sakes@tudelft.nl

Design of a Self-Propagating Tree-Root Inspired Needle

Tree roots are able to find their way through the soil towards a water source. They do this by growing their roots in a special way. First, they extend the middle part of the root into the soil. Second, they thicken the roots.

In this assignment, you will develop a soft tree-root inspired needle that is able to propel itself through the body in a minimally invasive way. The challenge will mainly lie in how you can propagate yourself through the body.

If you are interested in this assignment, please contact: Aimée Sakes, a.sakes@tudelft.nl

Tree-Frog Inspired Wall-Climbing Robot

The tree-frog is able to adhere to multiple surfaces. It does this by employing several strategies, one of which is the use of special “suction-cup” feet.

Based on this principle, in this assignment, you will develop a robotic foot inspired by the tree-frog. This robotic-foot can be used for many different applications. Think, for example, on medical applications, where you need to attach and detach quickly, but also on a wall-climbing robot!

If you are interested in this assignment, please contact: Aimée Sakes, a.sakes@tudelft.nl

Design and characterization of a soft gripper for slippery tissue

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.

Inspired by tree frogs, here, we will investigate whether firm but gentle grip on slippery tissue can be generated with grippers containing soft pads. With such a grasper, grip is still friction-based, but does no longer depend on the applied normal load. This probably

In this project, we will implement soft pads into 3D-printed graspers. The grasper design has to be adapted in order to generate load-independent grip. The project includes characterization of a prototype on biological tissues.

Start: January-February 2019

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

The Nothern Clingfish, Bio-inspired Suction Cup

The northern clingfish (Gobiesox maeandricus) is able to adhere to slippery, wet, and irregular surfaces in the marine environment. A study by Wainwright et al. (2013) found that the fish can adhere to surfaces with a broad range of surface roughness, from the finest of sandpaper, to highly irregular surfaces such as rocks. The fishes outperform manmade suction cups, which as many of us know, only adhere to smooth surfaces.

Clingfish are able to adhere to these wet and irregular surface due to their highly sophisticated suction disc. This suction disc consists of a cup with at the edge of the cup structured microvilli, similar to those of geckos. When the fish attaches to a surface, water is forced out from under the suction disc by rocking the pelvic girdle and an area of sub-ambient pressure is created. The microvilli at the edge of the disc, subsequently prevent slip of the cup or premature release by creating friction between the cup and the surface.

In this assignment we will focus on the design of a special bio-inspired suction pad for use in medical application to grip and release slippery, wet and soft tissue without damaging the structure.

If you are interested in this assignment, please contact: Aimée Sakes, a.sakes@tudelft.nl

Non-assembly 3D printed hand prosthesis

In developing countries, the accessibility to prosthetic devices is low due to the limited healthcare conditions, a general lack of technical knowledge and poorly equipped workshops. The introduction of 3D printing technologies has permitted new cheap and personalized hand prosthetic designs by bypassing many of the current manufacturing limitations of traditional prostheses. Although innovative and accepted in different settings around the world, these active 3D printed prostheses still require extra parts and assembly steps, thus reducing the overall accessibility. We have developed the first functional non-assembly prosthetic hand fabricated with the material extrusion technology; the most accessible 3D printing technique. The process is reduced to a single printing job and an extra step of support material removal. No extra parts, materials or complex assembly steps are required.

During the design process, we have also adopted ten design guidelines that led to a successful working mechanism, we encourage future designers with 3D printing to follow our non-assembly approach.

Publications

Media

Ten Guidelines for Non-Assembly A Prosthetic Hand is 3D Printed in One Piece with No Need for Assembly

Contact: Juan Cuellar (J.S.CuellarLopez@tudelft.nl)

Design of an Innovative Flexible Transport System (Closed)

During percutaneous coronary interventions in the coronaries of the heart, it is often a necessity to remove obstructions from the blood vessels. Obstructions are  removed using specialised instruments, such as atherectomy drills and balloon catheters. During removal, aspiration catheters are used in conjunction with these instruments in order to prevent small particles getting into the blood stream, which can cause a stroke, amongst others. These aspiration catheters use a pressure differential to remove the small particles from the blood stream.

Even though these catheters are successful in removing small particles from the blood stream, they are often plagued by various failure modes. For example, they are prone to clogging and are limited for transport of tissue through long and narrow tubes. Furthermore, the aspiration-force that is created does not only affect the desired tissue but also the surrounding tissue.

Therefore, in this assignment, you will develop a new type of flexible transport system that is not prone to these failure modes.

If you are interested in this assignment, please contact: Aimée Sakes, a.sakes@tudelft.nl

Minimum Assembly Bipolar Instrument

Complex medical devices, such as the EndoWrist, are difficult to manufacture and can often take up to a few week to assemble. In an effort to improve the manufacturability and assembly, in this assignment it is the aim to develop a medical instrument that minimizes assembly.

If you are interested in this assignment, please contact: Aimée Sakes, a.sakes@tudelft.nl

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