Conceptual Designs & Concept Selection
CoNCEPT ONe:
Shape-Memory Polymer Guidewire
The first idea is using shape memory polymer (SMP) technology to actively control the guidewire inside the arteries. With this technology, the team will select a polymer that is biocompatible and has a low soft phase transition temperature. The team will then heat at the polymer to varying degrees in its glass transition phase, let the material cool to “memorize” the shape and then repeat the process as needed. Once all forms of the shape memory polymer are “memorized”, the guidewire would then be ready for use and inserted into the catheter. Using a feedback control system, the surgeon would be able to regulate the temperature of the guidewire, manipulating the shape and form of the guidewire inside the patient, as he or she views its location under the MRI machine. In doing so, the surgeon will have the ability to prevent the temperature from changing too quickly and the feedback mechanism would have a built-in loop to prevent any mishaps from occurring.
CONCEPT tWO:
Magnetic Guidewire
The second concept is developing the idea of a guidewire controlled by magnetic fields. Essentially, the guidewire would be coated in a filament that is embedded with a multitude of magnetic nanoparticles, established from existing studies. The team would then have to create an external magnetic field, such that the surgeon would be able to automatically change the position of the magnet with respect to the guidewire inserted inside the body. However, the team would have to develop a mechanism that would not utilize magnetic imaging to scan the body and view the location of the guidewire inside the body for it would be affected by the magnetic field used to navigate the guidewire.
CONCEPT THREE:
Thermal Guidewire
The third concept is using thermal properties to utilize the temperature of materials to manipulate the direction and motion of the guidewire. The guidewire would be constructed out of two materials with different thermal expansion coefficients that are layered on top of each other. Through this difference in thermal expansion coefficients, the active process would manipulate this temperature change to navigate and control the motion of the guidewire. A feedback system with a control switch box would be connected to the materials that the guidewire is composed such that the surgeon would be able to manually change the temperature via the switches. The change in temperature would directly relate to the thermal expansion coefficients of their respective material which would, in turn, change its shape, deforming one of the materials on one side of the guidewire while not affecting the material on the other. This phenomenon would ultimately control the twists and bends of the guidewire through vessels of the brain.
CONCEPT FOUR:
Nanofiber Guidewire
The fourth design is to apply nanofiber to reach the goal to actively control the guidewire. One possible way is to utilize piezoelectric nanofiber because this kind of nanofiber can be controlled precisely. In this method, the guidewire was designed to include two separate parts, one is a “dummy layer” acting as the foundation and a layer of piezoelectric nanofiber attached to it. Because of the piezoelectric effect, when the nanofiber layer is electricized, it will deform to have various degrees of direction change. Moreover, the piezoelectric nanofiber is a micro-scope material, thus, it can be manufactured within the minimal size to reach the target cerebrovascular areas.
CONCEPT SELECTION:
After discussing and considering those four concepts, the group builds the concept selection matrix to help the group make a decision. There are seven selection criteria - complexity, material, manufacturability, cost, durability, operability, and biocompatibility - that being weighted into different weights. The result of the concept selection matrix shows that working on active guidewire made of shape-memory polymer is the best selection for us with a highest score. The excellent criteria of the shape-memory polymer include the high ability to manufacture and be biocompatible with patients.
