A Variable Stiffness Magnetic Catheter Made of a Conductive Phase‐Change Polymer for Minimally Invasive Surgery

Abstract

Variable stiffness (VS) is an important feature that significantly enhances the dexterity of magnetic catheters used in minimally invasive surgeries. Existing magnetic catheters with VS consist of sensors, heaters, and tubular structures filled with low melting point alloys, which have a large stiffness change ratio but are toxic to humans. In this paper, a VS magnetic catheter is described for minimally invasive surgery; the catheter is based on a novel variable stiffness thread (VST), which is made of a conductive shape memory polymer (CSMP). The CSMP is nontoxic and simultaneously serves as a heater, a temperature sensor, and a VS substrate. The VST is made through a new scalable fabrication process, which consists of a dipping technique that enables the fabrication of threads with the desired electrical resistance and thickness (with a step size of 70 µm). Selective bending of a multisegmented VST catheter with a diameter of 2.0 mm under an external magnetic field of 20 mT is demonstrated. Compared to existing proof-of-concept VS catheters for cardiac ablation, each integrated VST segment has the lowest wall thickness of 0.75 mm and an outer diameter of 2.0 mm. The segment bends up to 51° and exhibits a stiffness change factor of 21.

Shape-Memory-Alloys Enabled Actuatable Fiber Sensors via the Preform-to-Fiber Fabrication

“…Lastly, the smart actuator technology developed here offers the fundamental base for the potential close-loop control with simultaneous sensing and actuation functions. In the future, by incorporating additional SMAs or other stimuli-responsive materials, 6 the freedom of the dynamic movement could be further increased. These features promise to enable highprecision operations in microrobotic fields and advance further medical devices for diagnostic and therapeutic purposes.…”

“…Highly performing actuators with integrated sensing modalities offer possibilities in closed-loop control and high precision operations across micro-to-centimeter spatial scales, which is critically important to accelerate robotic and biomedical tool innovations. , In recent years, we have witnessed the significant advancement in developing such actuators based on stimuli-responsive materials, such as shape-memory alloys (SMAs), − shape-memory polymers (SMPs), and ionic or conjugated polymers . They offer advantages in flexibility, miniaturization, and cost-effective production, compared to the traditional hydraulic and pneumatic designs whose operation requires external pumps.…”

Multicomponent and multifunctional integrated miniature soft robots

“…Medical catheter and guidewire technology place an important role in minimally invasive surgery which could reduce surgical risks and shorten recovery times. [160][161][162][163][164][165][166][167][168][169][170] The catheter-based interventions have a wide range of applications in the treatment of cardiovascular diseases. 6,100,164 In addition to delivering the catheter to the designated location, a variety of challenging tasks need to be accomplished, such as monitoring physiological environment (electrophysiological parameters, temperature, and pressure, etc), applying electrical or thermal stimulation to soft tissue, delivering therapeutic drugs and cells, embolization and clot removal.…”

Shape memory polymer variable stiffness magnetic catheters with hybrid stiffness control

“…Michael Mattmann, Quentin Boehler, Xiang-Zhong Chen, Salvador Pané, and Bradley Nelson, are with the Multi-Scale Robotics Lab, ETH Zürich, Zürich CH-8092, Switzerland (e-mail: michaema@ethz.ch, qboehler@ethz.ch, chenxian@ethz.ch, vidalp@ethz.ch, bnelson@ethz.ch) the use of multiple tools simultaneously [20]. Despite the advantages of VS technology, scalable approaches are still limited to thermally induced stiffness transitions [15], [18], [21]- [25]. Our group has recently developed two scalable VS technologies that rely on a low melting point alloy (LMPA) and a composite shape memory polymer (SMP) [10], [20], [25], resulting in the smallest magnetically steerable variable stiffness catheters (VSC) to date.…”

“…Despite the advantages of VS technology, scalable approaches are still limited to thermally induced stiffness transitions [15], [18], [21]- [25]. Our group has recently developed two scalable VS technologies that rely on a low melting point alloy (LMPA) and a composite shape memory polymer (SMP) [10], [20], [25], resulting in the smallest magnetically steerable variable stiffness catheters (VSC) to date. However, both technologies pose considerable safety issues, as a failure in the heating system presents a risk to the patient that must be considered.…”