arXiv subjects

Ayhan Aktas

Publications and source records attributed to Ayhan Aktas.

5 recordsLinked to original sources

arXiv2026

Modular Robotic Catheters for Endovascular Aneurysm Repair

Fenestrated/Branched endovascular aneurysm repair (FEVAR/BEVAR) require surgeons to navigate catheters and guidewires into various branches of the abdominal aorta, before deploying stent grafts to alleviate pressure on the aneurysm. Previous clinical studies suggests that surgeons continue to struggle with vessel access using standard commercial instruments, prolonging the procedural time and inducing further complications. In this work, we present two contributions to solving this problem: 1) A bespoke 2-segment steerable catheter, consisting of 4 degrees of freedom to enhance dexterity. 2) An expandable, modular tendon-driven actuation platform that can accommodate for the redundancies introduced in our system. To fabricate the catheter, we capitalized on thermal fiber drawing, a technique that creates high-aspect ratio devices at scale, and processed the catheter with laser micro-machining to soften its tip. We evaluated the system using simulations, where we investigated the catheter's bending stiffness, then its steerability with in-vitro experiments in vascular phantoms. This handheld, robotic steerable catheter system has the potential to shorten the length of future endovascular surgeries, and give clinicians the tools to resolve challenging clinical cases.

cs.RO↗

arXiv2026

Investigating the Effect of a Series Elastic Actuation Retrofit to Black-Box Actuators

In robotic applications, actuators are typically designed to be stiff with minimal backlash to ensure precision and repeatability. However, this limits compliance, leading to potential damage and poor force control in uncertain environments. Series Elastic Actuation (SEA) introduces compliance to enhance disturbance rejection and enable force measurement via Hooke's Law but reduces system bandwidth. A custom Series Elastic (SE) element was retrofitted to a black-box actuator to mitigate non-linearities like backlash and static friction. Integrating the SE element enabled high-fidelity force measurements, improving force control bandwidth and performance. A torsional SE element was designed through Finite Element (FE) analysis, yielding a stiffness of 2155.4 Nm/rad. Open-loop force control bandwidth was measured for the original motor and the SEA-integrated configuration, while closed-loop bandwidth was assessed using feedback from the SEA and a commercial force sensor. The SEA module increased bandwidth from 10.32 Hz to 30.32 Hz, a 2.93X improvement. Additionally, it outperformed the commercial sensor by 7.63% despite costing 25 GBP, a fraction of the price.

cs.RO↗

arXiv2025

Thermally Drawn Bioelectric Catheters: Enabling Proprioceptive Endovascular Navigation

To navigate medical instruments safely and accurately inside a patient's vascular tree, combining X-ray fluoroscopy with intermittent contrast injections is the gold standard. However, prolonged exposure to ionizing radiation poses health risks, necessitates the use of cumbersome lead vests for the clinicians, and contrast injections can lead to acute kidney injury in patients. Bioelectric Navigation, a non-fluoroscopic tracking modality, aims to provide an alternative. It uses weak electric currents to detect local anatomical features in the vasculature and localize instruments without x-ray imaging. In this work, we advance Bioelectric Navigation on two frontiers. Firstly, we introduce a new class of bespokely designed electrode catheters. They are fabricated using 3D printing, thermal drawing, and laser micro-machining. Specifically, we manufacture a 6 Fr catheter incorporating 16 electrodes, a guidewire channel and an additional sensor compartment. We thoroughly assess the catheter's mechanical and electrical properties. Secondly, we introduce an algorithm to localize the catheter along the centerline of a vascular phantom, for the first time fusing electric detection of vascular geometry with electric distance estimation. We report both tracking accuracy and usability evaluated by an expert endovascular surgeon, demonstrating the strong potential of this technology for integration into the existing clinical workflow.

physics.med-ph↗

arXiv2025

Fabrication of Fibers with Complex Features Using Thermal Drawing of 3D-Printed Preforms

High-aspect-ratio polymer materials are widely utilized in applications ranging from everyday materials such as clothing to specialized equipment in industrial and medical fields. Traditional fabrication methods, such as extrusion and molding, face challenges in integrating diverse materials and achieving complex geometries. Additionally, these methods are limited in their ability to provide low-cost and rapid prototyping, which are critical for research and development processes. In this work, we investigated the use of commercially available 3D printers to fabricate fiber preforms, which were subsequently thermally drawn into fibers. By optimizing 3D printing parameters, we achieved the fabrication of fibers with diameters as small as 200 um having complex shapes, with features down to a few microns. We demonstrated the versatility of this method by fabricating fibers from diverse set of materials, such as fibers with different stiffnesses and fibers with magnetic characteristics, which are beneficial for developing tendon-driven and magnetically actuated robotic fibers. In addition, by designing novel preform geometries, we produced tapered fibers and fibers with interlocking mechanisms, also tailored for use in medical steerable catheter applications. These advancements highlight the scalability and versatility of this approach, offering a robust platform for producing high-precision polymer fibers for diverse applications.

physics.med-ph↗

arXiv2023

Towards a Procedure Optimised Steerable Microcatheter for Deep Seated Neurosurgery

In recent years, the steerable needles have attracted significant interest in Minimally Invasive Surgery (MIS). Amongst these, the flexible Programmable-bevel tip needle (PBN) concept has successfully achieved an in-vivo demonstration to evaluate the feasibility of Convection Enhanced Delivery (CED) of chemotherapeutics within the ovine model, with a 2.5 mm PBN prototype. However, further size reduction is necessary for other diagnostic and therapeutic procedures involving deep-seated tissue structures. Since PBNs have a complex cross-section geometry, standard production methods, such as extrusion, fails as the outer diameter is reduced further. This paper presents our first attempt to demonstrate a new manufacturing method for the PBN that employs thermal drawing technology. Experimental characterisation tests were performed for the 2.5 mm PBN and a new 1.3 mm Thermally Drawn (TD) PBN prototype described here. The results show that thermal drawing presents a significant advantage in miniaturising complex needle structures. However, the steering behaviour is affected due to the choice of material in this first attempt, a limitation which will be addressed in future work.

physics.med-ph↗