zwickiLine for Flexible Low-Force Testing
Catheters are used for many reasons, including transporting microinstruments integrated in a patient's body. They enable surgeons to make surgical procedures as minimally invasive as possible. A catheter can also help administer medicine directly to the infected area of the body or facilitate the use of stents to keep blood vessels open.
Engineers who develop these catheter systems and guide wires focus on reducing the coefficients of friction and breakaway torques. Zwick's horizontal AllroundLine testing machine makes it possible to determine the push force in a simulated catheter insertion with very high accuracy. The frictional behavior of the catheter is measured by pushing it through an artificial artery. This is known as the tortuous path. The test is carried out in a horizontal orientation to simulate the physiological status of the patient during surgery.
Zwick has developed a system specifically for this application that controls both the crosshead of the materials testing machine and a specially automated specimen grip. The horizontal AllroundLine testing machine provides space for 3D models and fluid baths above and below the main test axis. In a typical test, the machine pushes the catheter into the artificial aorta for a predefined distance. The specimen is then released and the crosshead returns to its initial position. The pneumatic specimen grips close again and the crosshead moves in the direction of the test. This sequence repeats itself until the catheter is completely inserted in the artificial artery. The fully automated test method makes it easy to test artificial aortas of various lengths. The following results can be determined with the machine software:
The results can be determined with a high level of accuracy. The extremely stiff load frame with digital control and drive systems is able to ensure that forces measured during the test originate from the sample under test and not from within the machine itself. The machine's control system has such a high resolution that it is able to position the crosshead of the machine to less than 1µm, and read forces to an accuracy of better than 0.5 % down to values of less than 0.1 mN.
Glide force test on catheters
Glide force test on urological and cardiovascular catheters with thermoregulation bath