Student projects

Modern axial blood pumps are increasingly being used as cardiac support systems. The pumps are characterised by a small design with a high flow rate.

In the project funded by the Senate Commission for Studies and Teaching (K1), the students will construct such an axial blood pump in an open design as a demonstration and study model.

The interdisciplinary approach of the project is interesting, as mechanical engineering, electrical engineering and physiological issues have to be addressed.

A functional axial blood pump model has now been successfully developed as part of the student project. The pump is driven by a self-constructed brushless DC motor (BLDC). The six windings (A+/A-/B+/B-/C+/C-) on the stator of the motor were wound by hand. The rotor blades were produced using 3D printing and are equipped with permanent magnets. Transferring electrical energy to the rotor inside the motor is not necessary with this configuration. The motor is controlled by an electronic 3-phase commutation, which also realises the speed control. The motor controller used for this purpose requires three Hall sensors (HA/HB/HC) for rotor position detection, which are positioned at 120° intervals on the stator. The axial blood pump is equipped with a magnetic bearing on the right-hand side.

Technical details:

• Brushless direct current motor (BLDC)
• Manually wound stator, approx. 300 windings/stator coil
• Motor control with 3-phase high-performance drivers
• Sensor-controlled commutation
• Hall sensors for detecting the rotor position
• Rotor consisting of impeller/inducer, diffuser, straightener
• Each created with 3D printer
• Equipped with magnetic bearings on one side

Advantages of the axial blood pump:

• Small, lightweight design with high flow rate
• Low blood damage due to special rotor design
• Magnetic bearing with low friction and heat generation, therefore wear-free and blood-friendly
• Low noise level

Supervisingprofessor
Prof. Dr.-Ing. Mehdi Behbahani
Room 01E12
T.: 0241-6009-53727
behbahani(at)fh-aachen.de

Contact

Supervising engineer
Dipl.-Ing. Karl-Heinz Gatzweiler
Room 01E09
Heinrich-Mußmann-Str. 1
52428 Jülich | Germany
T.: 0241 6009 53722
gatzweiler(at)fh-aachen.de

Student ProjectManagers
Simon Habicht
Chloe Radermacher
B. Bukhtawer

Deputy student project manager
Smit Nandu
Yashothan Sivarajah
Jan Faheem

Student assistants
Yuyang Mao
Tobias Küster
Naeem Assasa
Arefan, Aishan
Abdallah El Noaymi

More information
> Youtube
> Biomaterial laboratory

The rotational atherectomy procedure offers a fast and efficient method of treating stenoses in the vascular system.

Atherectomy is a minimally invasive procedure in which coronary and peripheral arterial occlusions are treated mechanically with minimal surgical effort. This includes the removal of plaque and calcium deposits that can occur as part of vascular diseases. "Mechanical treatment" in this case defines the dilatation (widening) of the vessel lumen without damaging the vessel wall through overstretching or injury [01-03].

Compared to balloon angioplasty, rotational atherectomy is a procedure that places less stress on the vessel wall. The occlusion material is "milled out" and not compressed against the vessel wall [04].

In the project funded by the Senate Commission for Studies and Teaching (K1), the students have now developed a demonstration model of a jetstream rotational atherectomy system.

The interdisciplinary approach of the project was interesting, as mechanical engineering, electrical engineering and physiological issues had to be addressed.

The demonstration model focuses on the visualisation of the treatment method, whereby the students learn about the structure and functions of the catheter system. Individual groups of students worked on the tasks in the various areas and, in consultation with each other, created a concept for developing the model, which then formed the basis for practical realisation. With regard to the model, questions concerning the flow behaviour within the vascular system with regard to stenoses and the necessity of the biocompatibility of such medical products were discussed.
The demonstration model serves the purpose of demonstrations in courses and lectures and practical trainings. The system can also be continued in future as part of students' final theses and mini-projects.

As part of the student project, a functional demonstration model of a rotational atherectomy system was developed. One of the focal points was the visualisation of the treatment method, for which a suitable scale of 20:1 was chosen for the model. The structure and functions of the catheter system can thus be precisely analysed. Collaboration between the students was encouraged by the project, which was also evident in the final assembly of the various components of the model, which are optimally harmonised with each other. However, there is still a need for optimisation with regard to the replacement material for the stenosis.

The demonstration model will be used in courses and lectures next semester. Instructions for using the model in practical training are still being worked on. Flow investigations using the PIV system (Particle Image Velocimetry) available in the laboratory are also planned in order to improve the flushing system, i.e. the outflow of dissolved particles.

References:

[1] (2016) Percutaneous mechanical atherectomy for the treatment of peripheral arterial occlusive disease. www.springermedizin.de/perkutane- mechanical-atherectomy-for-the-treatment-of-peripheral/8070018?fulltextView=true. Accessed 09 Feb 2020
[2] (2020) Atherectomy: A cleaning crew for the arteries. www.kardionet.de/atherektomie/. Accessed 10 Feb 2020
[3] DocCheck Medical Services GmbH (2020) Dilatation - DocCheck Flexikon. flexikon.doccheck.com/en/dilatation. Accessed 10 Feb 2020
[4] Lecture Rotablator (2019) Boston Scientific

Supervising professor
Prof. Dr.-Ing. Mehdi Behbahani
Room 01E12
T.: 0241-6009-53727
behbahani(at)fh-aachen.de

Contact

Supervising engineer
Dipl.-Ing. Karl-Heinz Gatzweiler
Room 01E09
Heinrich-Mußmann-Str. 1
52428 Jülich | Germany
T.: 0241 6009 53722
gatzweiler(at)fh-aachen.de

Studentproject managers
Melissa Rasiah
Marcel Spiertz

Deputy student project manager
Patrick Hannak

Student assistants
Smit Nandu
Insaf Issoul
Albakir Hala
Tesh Hamzeh

More information
> Youtube
> Biomaterial laboratory

Adhesive systems currently used in the medical field (e.g. plasters) usually have either too strong or too weak adhesive properties. They are also not reusable after the first application. Bionics, i.e. the adoption of technical solutions based on models found in nature, makes it possible to conduct research into new adhesive systems that are optimised by structural and physical effects. These materials have the following special features: they are reusable, self-cleaning and do not adhere to themselves.

Nowadays, some companies (e.g. Bender) produce so-called gecko tapes, in which tiny hairs are applied to a polymer surface using nanotechnology. These create bonds to other surfaces through van der Waals forces. This is referred to as dry adhesion. The application of such materials is possible in biomedical technology, for example for tissue adhesion.

This bionically inspired project aims to translate the natural movement and adhesion of the gecko into technology. The aim is to equip the feet with controlled individual toes so that adhesion to an angled dry surface is possible and detachment is also enabled. It is important to ensure that the weight of the gecko is kept low and that the dimensions of the toes or contact surface are optimised. As the adhesion system is an innovation in medical technology, the development of a gecko robot is all the more interesting. The Gecko robot can then be presented in lectures as well as in practical trainings and serve as a basis for further tasks (e.g. characterisation of Van der Waals forces).

The basic structure of the Gecko robot (1st prototype of the student project) is based on the "Bioinspired Wall Climbing Robot" from VeluxHelp on the "Instructables" website (still without electronic control). The motion sequence is now realised by a total of eight servomotors. The aim is for the gecko to be able to climb up smooth, steep surfaces using a special adhesive tape on its feet, the product Gecko® Nanoplast® from Gottlieb Binder. The adhesive tape is made of medical silicone and is based on the principle of Van der Waals forces. Gecko® Nanoplast® has 29,000 adhesive elements per 1 cm² and has a high adhesive force on all smooth, damp and slippery surfaces. www. binder.de/de/produkte/gecko-nanoplast/

Initial tests with the gecko robot showed that the adhesive force of the gecko tape on the feet was so great that the gecko could hardly get its feet off. The idea was to use additional servos and a sophisticated mechanism to enable the feet to unroll. For this purpose, a special flexible filament was used to create the feet in 3D printing in order to enable the feet to be rolled off or pulled off by pulling ropes on the feet, starting at the tips of the feet. The movement process is demonstrated in the video (2nd prototype of the Gecko robot).

In the meantime, a third prototype of the Gecko robot has been developed, in which the foot is designed as a kind of tubular shell. The foot is greatly simplified and designed for functionality in conjunction with the Gecko tape. The focus is on attaching the foot to the surface with sufficient adhesive force and on safely detaching the foot from the surface. This design is currently in the test phase. It shows that an optimised solution does not always have to be more complicated.

Picture credits (slides):

[1] Gecko https://www.spektrum.de/news/geckos-haften-anders-als-alle-dachten/1300069 (11/2021)
[2] Enlarged setae and spatulae of a gecko Favret, Eduardo A.; Fuentes, Néstor O.: Functional Properties of Bio- inspired Surfaces: Characterisation and Technological Applications. Singapore: World Scientific, ISBN 978-981-283-701-1 p. 105 (2009)

The process of anodising, which is frequently used in medical technology, enables the metallic material to be oxidised and thus the bonding of an aluminium oxide layer (ceramic). The process is to be designed as a practical experiment in which the students experience the correlation between various parameters and the quality of the coating. The aim is to promote materials science on a chemical, mechanical and electrotechnical basis.

The long-term use of the various medical implants requires future medical technology engineers to expand their knowledge of the various manufacturing and coating methods. In particular, ceramic coatings can significantly improve the biocompatibility of metal implants.

The anodising process is highly temperature-dependent. It is necessary to heat the system for the first time without exceeding a certain temperature and then cool the system. An automated cooling unit is set up for this purpose. This device makes it possible to define the framework conditions and keep them constant for various experiments.

After the cooling unit has been set up, the coating is applied. For this purpose, a device is constructed which is connected to a circuit in which the material to be coated is the anode. The smooth aluminium surface, i.e. the anode, is enriched with aluminium oxide particles through oxidation. The coating quality depends on various parameters. These include the aluminium oxide concentration of the electrolyte, the temperature and the current strengths, the influence of which is investigated.

The subsequent characterisation of this coating is carried out using two methods. On the one hand, this is carried out with the support of external Institutes, which enable visualisation methods using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The former enables visualisation of the microstructure at a magnification of up to 150,000 times, while the latter enables detailed element analysis. Resistance measurement can also be carried out within the institute. The measured resistance is dependent on the coating thickness.

The findings of these analyses can be used to set up a practical experiment in which students are introduced to the anodising method.