Guidewires are involved in a huge range of medical procedures, which typically involve the guidewire being inserted into the vascular system and threaded through almost 2 metres of blood vessels to deliver devices such as stents or remove blockages in the vessels. With only a small incision, the guidewire allows these treatments to be delivered deep into critical vessels, for example in the heart or brain, minimising the trauma to the patient. Of course, this requires the surgeon to precisely control a device which they can’t see and is located at the opposite end of a twisted two metre wire, sometimes under time-critical emergency conditions.
Guidewires are therefore carefully engineered using advanced materials and coatings to make them as controllable as possible; one such combination being a nitinol guidewire with a PTFE coating.
Nitinol is an alloy of approximately 50% nickel and 50% titanium with some unusual properties that make it an excellent material for guidewires. It is superelastic, meaning that it can undergo extreme amounts of twisting and bending and still return to its original shape. This allows a nitinol guidewire to travel through the tortuous pathways of the vascular system without developing kinks or other damage that would ruin the operators control over the wire. The same superelasticity also means that the wire places less stress on the walls of vessels through which it passes, protecting those vessels from damage.
To further improve control of the wire and reduce stress on vessels, low friction coatings such as PTFE are typically applied to a guidewire so that it slides smoothly and can be inserted and positioned quickly and accurately. These coatings enhance the performance of the wire but must meet some challenging requirements to operate effectively and reliably. The coating needs to withstand the same tortuous twisting and bending as the superelastic guidewire without cracking or debonding from the wire. PTFE is well known as a non-stick material so achieving the required bond to the guidewire poses an interesting challenge. This has traditionally been overcome with the use of priming agents such as perfluorooctanoic acid (PFOA), but PFOA is now being phased out under improved environmental and health regulations leaving guidewire manufacturers in need of a replacement.
This is where CoBlast comes in. In a study to be published shortly in the journal Shape Memory and Superelasticity we applied PTFE to nitinol plates and wires using CoBlast. The process is simple and environmentally friendly; it is solvent-free, primer-free, and requires no heat input. The resulting PTFE coating is low-friction, thin, flexible, wear resistant, and well-adhered: everything required for the ideal guidewire coating.
The full peer-reviewed article will feature in an upcoming issue of Shape Memory and Superelasticity and is currently available online at: