Drug-eluting balloon (DEB) and drug delivery catheter (DDC) based treatments are increasingly being offered and used for the treatment of coronary, peripheral, neurovascular, and ENT applications. European markets have already seen a larger acceptance of these therapy choices ahead of the US markets. However, large randomized studies are underway in various stages of data collection to clearly quantify the advantages of balloon catheters over drug eluting stents, longstanding procedures like percutaneous transluminal angioplasty, surgical interventions (e.g., atherectomy or grafts), and drug therapy-like tissue plasminogen activator.
Various clinical trials have produced data that indicate the balloon design (specifically its ability to deliver drugs at both the correct location and improve drug uptake) and the procedural techniques used to be among the major factors that determine the success or failure of a therapy. Design concepts include hole/opening size and density, complex geometry of the balloon and catheter with multiple lumens, and surface structure modifications while maintaining a vigil on cost control.
Advances in laser micromachining technology — which include the capability of compensation for material and geometry variations and feature placement — offer device engineers an expanded toolbox to create better DEB/DDC devices, as well as keeping costs under control.
Laser Micromachining: A Brief Primer
In its broadest sense, laser micromachining applies to a specific window of all laser manufacturing where the feature sizes range between 1 μm and 1 mm. The features can be measured as size, depth, or density. Running a large gamut of wavelengths, lasers offer material removal methods based on a thermal process (400–10,600 nm visible & IR lasers like Nd: YAG or CO2) or a photochemical ablation process (<400-nm UV lasers like excimer or higher harmonics of solid state lasers). In addition, the latest buzz in the industry is from ultrafast lasers — material removal is determined less by the wavelength and more by the extremely high energy densities (temporal and spatial) delivered in a pico- or femtosecond timeframe. A typical laser micromachining system has four components: laser source, optical system for laser beam delivery, mechanical system for device handling and manipulation, and camera vision and software controllers to integrate all the components.
For thin-film metals and polymer devices, UV laser technology enables devices to be manufactured according to a highly desired combination of smallest feature sizes and highest quality. This is possible due to non-thermal material removal and the inherent high resolution of short wavelength light.
To offer a comprehensive and successful laser manufacturing solution, the provider must answer three fundamental questions:
1. What type of laser and starting parameters should be used (based on material)? 2. What is the optical design (based on feature spec and cost)? 3. What mechanical system should be used (based on feature location and device geometry)?
Catheter Micromachining — Laser Manufacturing Advantage
Catheters are the primary mode of delivering devices, drugs, and surgical tools through ports to the human body. Coronary, peripheral, neurological, renal, and gastrointestinal diseases requiring intervention use catheters therapeutically.
The peripheral arterial disease (PAD) market is a rapidly growing market for development and treatment. With a gradual reduction in profits from the established interventional cardiology arena, device manufacturers are encouraging a larger investment in PAD. Drugs, stents, atherectomy, graft, balloons, and a combination of these therapies can be used to treat peripheral diseases. To that end, catheters are used as a delivery vehicle and current designs improve on drug delivery and arterial wall uptake, mechanical plaque breakdown, and subsequent removal.
The neurovascular market is seeing significant growth from therapies that target aneurysms, tumors, ischemic stroke, and neural vascular malformations. Micro-catheters are used in conjunction with stent-type retrieval systems to treat and remove emboli. Coils are inserted in skived ports in catheter lumens to deliver targeted therapy for preventing rupture of aneurysms and/or neurostimulation.
Laser micromachining of catheters offers the ability to include design elements for improvement of, for example: drug delivery, smaller catheter size for reduction in post-treatment recovery, position and design of ports, and selective removal of coatings on braided catheters to improve flexibility.
The following is an example of drilling holes and skives at specified locations on a polymer multi-lumen DDC. Common materials chosen for catheters include Pebax®, nylons, and fluoropolymers (e.g., FEP and polyimide). Various design and material challenges are presented and solved with new advancements in laser micromachining. (See Figure 1)
Design Criteria: Uniform precise holes less than 100 μm in diameter and skives with no bulk material damage