Development of a process for zero-particulate laser machining of medical devices in a clean manufacturing environment (ZEROMED)

 Laser drilling and micro-milling is emerging as a key step in the fabrication of the next generation of catheter-based devices for precision-flow applications.

The aim of the project is to develop a laser-based process for the machining of small (micron-scale) dimension features in polymer materials with a substantially reduced level of particulate generation. The process will be initially focussed on applications in the manufacture of devices, assemblies and sub-assemblies for use in the medical field, in particular, on catheter-based precision-flow devices.

 The process will be based on the use of a solid-state laser and fluid-assist to drill holes and mill custom features in medical polymers. The laser delivers a high energy beam to a highly localised point allowing high-precision machining, through melting and ablation of features. The fluid, which will be delivered co-incident to the laser on the sample, has a number of functions, namely:

• to dampen the generation of particulate from the process,
• to trap and transport any particulate that is generated,
• to act as an accelerant to the process by increasing the efficiency of the laser-material interaction.
• To minimise collateral damage to the machined part

The project will focus on the optimisation of the process via a number of research strands; identification of the mechanisms governing the fluid-assist process in order to maximise the desired cleaning effects, identification and selection of the most appropriate fluids, and the development of a suitable demonstrator process (with associated fixturing, beam and fluid delivery). The laser process will offer a viable, enabling and cost effective manufacturing solution for a wide range of medical devices based on precision-drilled polymer materials. It is expected that the joining of this fluid-assist process with new diode-pumped solid-state (DPSS) lasers operating in the UV spectral range will accelerate the integration of laser machining technology into manufacturing environments by making the processes compatible with both high-volume manufacturers and the requirements of cleanroom-based manufacturing protocols.

For more information on these activities, please contact:  Tony Flaherty, email:

National Centre for Laser Applications
NUI, Galway
Ireland
Telephone: +353 91 493595
Fax: +353 91 494594

The miniaturisation of chemical diagnostics and chemical synthesis systems is the principal driver for the research proposed in this project. Micro-fluidics and micro-reactors are emerging as a significant platform technology in analysis -such as bio-diagnostics, sensors, etc. and in chemical synthesis -such as micro-reactors.  While a number of materials can be used, components developed to date have centred on silicon and glass.  Polymers are expected to emerge as a very significant material in future high volume and single use-once applications. The production technologies used in the creation of the millimetre-sized devices or chips, on which the micro-fluidic pathways and reactor channels are machined, range from micro-moulding, hot embossing, mechanical imprinting to laser-based ablation. This project targets the latter, in particular the development of interactive laser beam delivery technologies that can be used for significant optimisation of laser ablative processes. These technologies will enable the properties and quality of the laser beam to be continually modified in real time during laser processing, creating more complex processes with greater precision. The improvements will have significant impacts in the production of superior micro-fluidic pathways, both in terms of enabling novel structures and in improving rapid turn around of prototype devices.

Over the last three years, researchers at the NCLA have been engaged in investigating micro fluidic channels for biomedical applications. The consensus from this industry is that surface finish is critically important, in particular its ability to position molecules for diagnostic applications. Careful control and optimisation of specific surface properties is a key advantage for laser technology over other technologies. Rapid prototyping is also identified as being very important. The ability to produce a number of variants/iterations of a design quickly and cost effectively is critical to the iterative optimisation of the micro-fluidic device.

The completion of the project will realise the following specific technical objectives pertaining to interactive laser beam delivery system:

Surface engineering is a rapidly growing area of research covering a diverse range of applications in the manufacture of plastic products. This project investigates the applicability of optical surface modification techniques to improve the performance of polymer materials in two related areas, namely enhancement of biocompatibility or bioactivity, and the optimisation of adhesive bond strength. These functions rely on the wettability of the polymer, which can be controlled by adjusting the surface energy and hydrophobicity/hydrophilicity of the surface via one or more of the following mechanisms. The project seeks to develop techniques that will employ UV light generated by lasers and lamp sources to effect surface modification through the mechanisms described above. Recent developments have shown that optical techniques have considerable potential in this regard. The key advantages will be the highly controllable output possible from optical sources and the ability to focus the light onto selected areas with a high degree of spatial resolution. The effects of irradiation will be quantified through a comprehensive range of analysis techniques including contact angle measurements, surface profilometery, Raman and infra-red spectroscopies, optical and scanning electron microscopies, XPS and SIMS. In the case of adhesive bonding mechanical strength tests and post-testing failure mode analysis will be performed.

The objective of this project is to develop high quality laser micro-machining processes where no thermal damage is evident in materials.  The initial stages of the project were concerned with the commissioning of a high peak power femto-second laser from Clark-MXR, integration of optics and beam handling, development of mechanical actuators for the system, and performing laser tests, and initial machining trials with an integrated air-bearing motion system.   Work is now being performed on percussion and trepanning drilling of silicon wafers and metals.  Work has also focussed on examining the propagation of ultra-fast laser pulses in air, and the resulting laser beam quality M², and the investigation of different optical configurations.
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Biomimetic Surfaces for Orthopaedic Implants (BioMimSurf)

NCLA is pleased to announce the funding of the above project through the Commercialisation Fund – Technology Development programme operated by Enterprise Ireland.  Starting in December 2003, the project has been funded for three years, and builds on the platform of an on-going collaboration between the NCLA and National Centre for Biomedical Engineering Science (NCBES).  The project will investigate the use of monochromatic ultra-violet (UV) light from excimer laser and lamp sources to modify the surfaces of plastic materials.  The technology will be targeted primarily for use in orthopaedic implants.
In general terms, the basic problem to be addressed is that medical plastics have poor compatibility with biological environments.  Despite this fact, they are indispensable as biomaterials because of their bulk properties and low cost.  However, the bioactive properties of these materials can be improved by exposing the surface of the polymer to ultraviolet (UV) light from an excimer source (laser or lamp).  Broadly speaking, UV light has two distinct effects on polymers:

A combination of these approaches will be employed to generate an environment that is more closely related to that normally experienced by cells – a so-called biomimetic environment.
The project will concentrate on developing the processes and characterising the materials in vitro to a level at which it will be possible to assess suitability for commercialisation in working devices.
In the implant, the plastic material forms the outer layer of the shaft of the device which is inserted into the bone.  The successful conclusion of this project will facilitate the enhanced integration of the shaft with the surrounding bone through the use of inexpensive, easily processed materials.  The healing process will be shortened and the durability and longevity of the implant increased – all of which is ultimately good news for medical practitioners and their patients.

The optimum surface designs will be identified via three interlinked experimental strands:

The above Enterprise Ireland Commercialisation Fund – Technology Development project has been awarded to the NCLA for a period of three years. The project starts in  December 2003, and will extend the micro-machining research base in NCLA to the emerging area of novel drug delivery systems.

At a general level, the project will target the development of laser drilling, micro-machining and structuring processes for use in medical devices that are designed for drug delivery, and for implants in which the integration of drug delivery components will form an additional function.

With regard to the former, the project will target the development of damage free micro-holes with engineered profiles suitable for high volume production of drug delivery components such as drug atomizers.  With relevance to implanted medical devices the project will target the development of processes for controlled drug release. It is intended to develop platform laser processes for use in diverse processes and products for enabling metered drug doses.

At a technical level the project will seek to develop innovations in laser ablation based on novel optics, assisted processes and novel application of state of the art laser sources.  State of the art laser sources including femtosecond, frequency tripled and quadrupled all solid state lasers will be used.

The overall objective of the project is to develop laser ablative processes and disseminate the academic results in international journals in the filed of science and engineering and develop commercially exploitable intellectual property from these developments.