Bill Peatman, consultant content strategist and writer for Microlution
Machining parts small enough to be deployed through vascular catheters is challenging. One company has found a way to produce a new type of ablation catheter tip, namely using ultrafast laser technology to create micro holes to deliver more efficient, precise treatment.
The medical device manufacturing industry is one of the most challenging and exciting industries in the world. New devices are saving and extending lives, and implantable and minimally invasive devices are speeding therapies, reducing or eliminating hospital stays and accelerating recovery times. Machining these devices and the components that make them work, however, is becoming increasingly difficult. Parts must often be small enough to travel through human veins, perform complex procedures, and meet all government safety and quality requirements. New machining technologies are now making exciting new products possible.
Catheter ablation
One area in which machining technology is enabling safer, more effective devices is catheter ablation for arrhythmia. The human electrical system sends signals to the heart to pump blood throughout the body. This system does not always work correctly. Cells may send irregular signals, making the heart’s chambers flutter randomly, causing what is known as arrhythmia. An increasingly common treatment for arrhythmia is catheter ablation, where a catheter with an electronic tip is guided to the heart to cauterise the source of the harmful signals.
Critical success factors for catheter ablation include: directing the tip to the exact source of the faulty electrical signals; and generating sufficient electricity to fully ablate the harmful tissue without damaging healthy tissue or, more seriously, over heating to cause scars or blood clots (thrombus). Most ablation catheter tips feature imaging and sensing technology to identify the exact tissue to be ablated and to monitor the heat generated by the ablation to keep the temperature in a specified range. However, reduced temperature can make it difficult to create a lesion large enough to ablate the entire surface area at the arrhythmia source. Larger tip catheters can ablate more tissue, more quickly, but with varying tissue thickness throughout the heart, smaller tips are also used to treat smaller areas.
Irrigated ablation catheter tips
Many newer ablation catheter tips employ irrigation, which involves flushing saline solution around or through the tip to keep the area cool enough to perform a successful ablation. The risk of introducing fluid into the ablation area is that the heat can cause it to boil, release steam or gas, and perforate the heart tissue.
New designs for irrigated tips make irrigation more efficient, affording increased cooling action using less fluid and therefore a reduction in the risk of boiling. This is achieved by designing holes to precise geometries to manipulate liquid dispersion. Machining these holes, which are smaller than the diameter of a human hair, has been economically unfeasible with traditional machining technology. Achieving the precise dimensions, with the edge quality and surface quality required for more efficient dispersion, demands a level of precision and speed not found in legacy micro manufacturing technology.
Ultrafast laser technology
Johnson Matthey, a manufacturer of components for the medical device industry, has discovered that ultrafast laser technology allows for the realisation of the new irrigated tip designs. Ultrafast lasers remove material without generating heat, enabling the machining of tiny holes with sufficient surface and edge quality to bring new irrigated tip designs to life. Irrigated tips manufactured using ultrafast lasers require half the liquid flow of those manufactured using traditional techniques. This reduces the risks of both thrombus formation and perforation.
The most common challenge of any machining process is managing thermal damage to the part. Heat causes melting, burrs, recast and other damage that must be addressed in post-processing. For parts as small as catheter tips, just about any thermal damage is unacceptable as it is extremely difficult to perform rework at micron-level dimensions. Ultrafast lasers work by sending pulses of light so quickly that each pulse removes a small amount of material before heat can be absorbed. The result is that the shapes, in this case, the holes in the catheter tips, are near perfect. The dimensions, surface and edge quality matches the designer’s specifications to allow for more accurate liquid dispersion.
Although ultrafast lasers have been used in laboratories for decades, they are not hardened for industrial use and are susceptible to environment conditions such as temperature change and vibration. Microlution is a specialist in the commercialisation of ultrafast laser technology, developing platforms with the stability, enclosures, part handling capabilities and motion control required for their successful deployment in a number of automotive, medical and semiconductor factories globally. Together, Johnson Matthey and Microlution have developed an automated and cost-effective laser machining system for the manufacture of advanced irrigation tip ablation catheters (Figure 1).
Figure 1
The Microlution ML-5 is the core ultrafast laser micro machining platform used by Johnston Matthey to machine advanced irrigation ablation catheter tips.