Balloon catheters are commonly used in the deployment of stents during angioplasty. As the balloon is inflated, the stent expands and pushes against the artery wall. The balloon catheter is then deflated and withdrawn while the stent permanently remains in the artery to keep the artery open. Dislodgement of the stent from the balloon catheter before it reaches the targeted location can severly injure the patient. Therefore, it is essential for manufacturers of these devices to provide products that have been carefully and thoroughly tested to ensure that the expandable stents are delivered safely or can be removed from the target site without the danger of losing a stent.
Recently, we were asked to provide a suitable system that could be used to perform tests to determine the force required to pull out the stent axially from the un-inflated balloon catheter. Because of the nature of these devices, a gripping solution can be a challenge. We needed to provide a gripping technique that is capable of holding the specimen firmly, without damaging the stent.
For this test, we used our table model electromechanical machine, equipped with a 100 N loadcell, custom compact pneumatic versa grips, and custom rubber-coated jaw faces. We wrapped pieces of various adhesive tapes around the stent to cushion against excessive pressures, as well as to serve as tabs. The types of adhesives we used were a critical role in holding the stent during the test. For effective testing, the adhesion force between the stent and the adhesive tape must be stronger than the stent dislodgement force. Our Bluehill® 2 Software tension module is well-suited for measuring the force required to move the stent relative to the balloon catheter.
The test results obtained with the above configuration not only provides information on how well an existing product performs, but also provides insight on how existing products can be further improved upon.