Bright ideas: Blueacre Technology offer their expertise

David Moore & David Gillen, Blueacre Technology, offer their expertise when it comes to the laser processing of catheters.

A number of factor have to be taken into account when laser micro machining of polymer catheters. Compared with metals, polymers are more flexible and tend to move during processing. This problem becomes more significant when machining small features (<50µm) on thin-walled tubes. The ability utilise machine vision track the tube position in real-time, allows for high cutting speeds while holding tight tolerances of +/-5um over long parts.

In the past pad printing of inks onto catheters has been the main process whereby marks are added as indicators of position or for part traceability. However with advances in how laser beam delivery have been integrated with part handling systems, it is now possible to laser mark over the full length of a catheter device.

Blueacre Technology has developed equipment capable of marking over catheters over a metre in length. As the marks are part of the catheter material, they do not suffer from bio-compatibility and fading issues associated with traditional pad printing techniques.

Catheter finishing

One of the issues with cutting the end from a braided catheter it that there is no longer a restraining force on the braid, which can un-coil. Figure 2 shows a catheter that has been cut using a laser process developed by Blueacre Technology. This cutting process prevents the braid from un-coiling and allows a distal tip to be over molded without an increase in profile diameter.

As medical technology develops so does the demand to cut holes in the side walls of catheters. There are a number of applications for catheters with such side holes, from drug infusion to arterial flushing. The core requirement for side holes is to produce a feature that has a clean edge without any burr or raised portions.  An example of catheter holes in a polyimide catheter are shown in Figure 3.

Laser machining allows holes down to 10um in diameter to be drilled with both high precision and tolerance. It is also possible to machine very clean features in multi-layer materials that include PTFE/Nylon combinations.

The drilling of side holes in braided catheters has a number of issues, as the inclusion of a metal layer adds increased process requirements on the laser. If the hole is not machined with minimal heat input, the outer layer can soften, the braids can push outwards and the profile increases. In the worst case scenario the braids can protrude through the outer layer leading to the possibility of trauma. Figure 4 shows images of holes drilled into the sidewall of braided catheters and with careful choice of laser parameters it is possible to cut clean holes with no damage to the braid.