Spotlight on Surface Treatment
Implant coating
A company specializes in the surface treatment of all types of implants. Titanium, cobalt-chromium, hydroxyapatite, and aluminium coatings are applied using plasma-deposition techniques to produce micron-thin layers. Plasma spraying can be conducted under vacuum or atmospheric conditions. The firm has particular expertise in coatings that improve adhesion between the implant and the cortical and spongy bones. Certified to EN 46002, the company also supplies related packaging services for medical and surgical equipment. Coating Industries, Villeurbanne, France.
Aluminium coating
Because it exhibits high conductivity and ductility as well as long-term stability, aluminium is frequently used to shield plastic housings. A company has developed a process to selectively coat moulded plastic parts with aluminium. In a high-vacuum environment, the metal evaporates and condenses on the surface of the substrate. The layers, which are typically 2.5, 5, or 10 µm thick, achieve a shielding efficiency of up to 80 dB. To ensure long-term stability of aluminium in corrosive environments, a protective coating can be deposited during the same vacuum cycle. The protective material is less than 0.5 µm thick and will not hamper electrical contact between parts. Additional advantages of the Elamet coating process include transparency and good adhesive and scratch-resistance properties. Coated materials have successfully passed IEC 68-2-42, DIN 50017 KK and KFW, and DIN 50021 SS tests. GfO, Schwäbisch Gmünd, Germany.
Plasma-treatment services
Plasma-based surface-treatment services are developed and supplied for a variety of medical devices. Applications include enhancing lubricity in catheters, increasing wettability in fibres and threads, reducing friction in needles, and improving adhesion in joined materials. The surface treatment can be used alone or with other processes. Company engineers routinely develop treatments based on customer requests. Biomat snc, Roveretto, Italy.
Surface-treatment equipment
A machine coats devices with diamondlike carbon (DLC) by means of plasma-assisted chemical vapour deposition. DLC coatings improve a material's biocompatibility, lubricity, and resistance to wear and corrosion. A radio-frequency field generated by a 1-kW power supply ionizes the gases; as many as four gases can be introduced during different stages of the coating process. The system can be operated manually, semiautomatically, or automatically. In automatic mode, 20 time periods, ranging from 0.01 second to 99 hours, can be programmed, and up to eight control outputs are available within each period. The equipment can be supplied with chambers suited for specialized applications: a 30-cm-diam unit is designed for coating stents and other small devices, while a 1-m-long tubular chamber is adapted to the treatment of guidewires. By introducing the appropriate gases, manufacturers can use the system for etching applications and for the deposition of other coating materials. Diavac ACM Ltd., London, UK.
Guidewire coating
A thin, flexible coating that adheres to wet or dry metal substrates is suited for the surface treatment of guidewires and related devices. Slip-Coat hydrogel coating immediately becomes slippery when it comes into contact with body fluids or water, allowing for easy and safe manipulation of invasive devices. The coating is permanent and nonthrombogenic, enabling manufacturers to produce low-cost biocompatible instruments without having to use substitute materials, according to the company. Previous formulations of the coating have been used to successfully treat devices made from various polymers, titanium, and nitinol. The company also provides packaging, sterilization, and testing services. STS Biopolymers Inc., Henrietta, NY, USA.
Plasma reactor
Designed for low-volume production and research purposes, a microwave plasma reactor is compact enough for benchtop applications yet delivers fast, repeatable processing runs with low thermal loading. The unit features resist removal at up to 1 µm/min and can clean ceramics and glassware; it is also suited for the surface treatment of plastics. Power is supplied via a free-running 2.455-GHz magnetron; a wave-guide-coupled multimode resonant cavity incorporates a low-pressure vacuum chamber and two feed gases. The reactor is available with a 100- or 190-mm-diam internal chamber; power levels can be configured to suit various applications. Gas-flow, microwave-power, and temperature interlocks ensure operator safety. Cambridge Fluid Systems, Cambridge, UK.
Electrical surface treatment
Designed as an economical alternative to plasma-based processes, electrical surface-treatment (EST) equipment improves the bonding properties of adhesives, inks, and coatings. EST systems can operate in low-frequency configurations for partial treatment at low speeds or in high-frequency mode for the uniform treatment of larger products at high speeds. Both types of systems can operate on- or off-line at production speeds. The treatment's efficacy can be measured either by contact-angle or surface-energy methods. Applications include polystyrene culture-grade products, disposable syringes, angioplasty catheters, tubing, diagnostic products, and related devices. The company also offers a low-pressure plasma system, a less-costly alternative to conventional plasma-treatment equipment. Tantec A/S, Lunderskov, Denmark.
Multifunctional surface
treatments
Reagents that are photochemically attached to a surface by means of stable covalent bonds can be combined to modify more than one surface characteristic at the same time. One PhotoLink coating can reduce the surface friction on a medical-grade polymer, for example, while a second reagent reduces the risk of thrombus formation. This technology can be used to enhance such surface characteristics as lubricity, wettability, haemocompatibility, and antimicrobial properties. Tissue engineering, drug delivery, and biomolecular immobilization are among other applications. BSI Corp., Eden Prairie, MN, USA.
