Company insight
Turn down the heat in polymers with ‘cold lasers’
Cutting, welding and marking of plastics and polymers when fabricating precision medical devices requires maximising device performance and ensuring patient safety. IPG Photonics explains how ultrashort laser pulses use ‘cold ablation’ to enable medical device manufacturers to create these critical polymer components without excess heat.
and quality. Fibre lasers in particular have seen widespread adoption due to their ease of integration and reliability. However, there is no such thing as a one-size-fits-all fibre laser – parameters like pulse duration and energy have a dramatic impact on quality. Lasers most often emit a continuous or nearly continuous beam of light to output a steady stream of average power – this mode of operation is referred to as continuous wave. Lasers can also be used in a pulsed mode of operation. Ultrafast pulsed lasers, also referred to as ultrashort pulse lasers, utilise extremely short pulses of focused light measured in femtoseconds or picoseconds. In practical terms, ultrafast pulse durations mean that laser energy only interacts with the target material for as little as a few trillionths or quadrillionths of a second, which significantly reduces heat imparted as compared with continuous wave processing. Lasers can also operate in pulses measured in nanoseconds, although these lasers are not typically referred to as ultrafast due to the comparatively long periods that nanosecond laser pulses interact with the target material.
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The power of ‘cold processing’ The ultrafast moniker is reserved for a non-thermal regime of energy absorption. Ultrafast lasers deliver exceptionally high peak power without inducing thermal effects on surrounding materials. This extreme peak power results in multi- photon absorption by the target material. The simplest case is second harmonic generation (SHG) where the energy of two photons simultaneously combine when interacting with a material to generate a photon with two times the energy.
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aser materials processing is used across virtually every material, application and industry due to its high precision, speed
(A) The edge of a polycarbonate blind disc machined with a nanosecond laser that displays excessive melting. (B) The edge of a polycarbonate blind disc machined with an ultrafast laser displaying virtually no melting.
The ultrafast pulse duration greatly limits the time available for heat to diffuse into the material surrounding the part feature. The result is ‘cold ablation’ where individual pulses remove an extremely small volume of material as vapor while creating virtually no heat-affected zone. The same laser-material interaction principles do not apply to nanosecond pulsed lasers and the thermal impact of laser processing only increases with longer pulse durations.
Excess heat is not a critical consideration in every application, such as in industrial thick metal cutting or welding, but it must often be avoided in polymer processing for medical devices. Excess heat can cause melting, foaming, carbonisation and combustion in sensitive polymers, rendering these devices unusable. As a result, ultrafast lasers have seen a steady increase in use for a variety of medical devices such as medical tubing and catheters as well as various sensors for monitoring equipment. The benefits of ultrafast laser processing extend beyond just reduced heat-affected zone. The high peak power of ultrafast lasers enables the creation of permanent UDI marks critical for traceability and compliance. Ultrafast lasers also offer unmatched control over the precision and size of medical device features such as cut
widths and hole sizes. This enables engineers to better optimise polymer part designs for improved performance.
Getting started with a laser solution Choosing the right ultrafast laser and laser process is the most important part of maximising quality and throughput in medical device applications. IPG Photonics operates state-of-the-art global application labs to offer the world-class process development required for precision polymer processing. Medical device manufacturers provide IPG with samples for evaluation or part specifications and receive detailed reports for their laser processing options. Experienced application engineers and laser scientists optimise laser parameters to develop laser process recipes to match each application and design specification. Once a process is refined, IPG offers turnkey and custom laser solutions purpose- built for medical device manufacturers to improve their current processes and enable new device creation in the future. IPG takes a lifecycle approach when working with medical device manufacturers to ensure that every laser solution is fully supported from its initial use through optimisation. ●
www.ipgphotonics.com Medical Device Developments /
www.nsmedicaldevices.com
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