Medical Device Link.

Photochemically attached through stable covalent bonds

BSI CORP. (Eden Prairie, MN) has developed a line of surface-modification reagents that can be combined to bring more than one surface characteristic to medical devices simultaneously. The light-activated PhotoLink reagents are chemically attached to surfaces through covalent bonds, resulting in a predictable, stable coating with controlled intramatrix cross-linking. According to the manufacturer, this multifunctional capability is not possible with other technologies, which require completely different processing steps to produce each surface characteristic.

For example, one PhotoLink coating can reduce surface friction by 60­90% on a variety of commonly used medical-grade polymers. Another can reduce thrombus formation to improve the hemocompatibility of surfaces. When these two reagents are combined, they provide a slippery coating that also reduces the risk of the formation of clots on devices inside blood vessels. Likewise, coatings that reduce a surface's affinity for bacteria and provide lubricious or hemocompatible characteristics may be bonded simultaneously to medical devices.

PhotoLink reagents provide a variety of surface properties to a wide range of materials. Achievable properties include improved lubricity, wettability, and hemocompatibility; antimicrobial characteristics; reduced protein and cell adhesion; and functional surfaces for biomolecule immobilization. Three separate antimicrobial coatings are available: a hydrophilic coating that reduces a surface's affinity for bacteria; a hydrophilic coating incorporating an antimicrobial agent that is released slowly over time; and a coating that contains a photochemically immobilized antimicrobial agent for long-term antimicrobial activity. The PhotoLink reagents are also suitable for use in tissue-engineering and drug-delivery applications.

For more information, contact BSI Corp. at 612/829-2701.

Features a shrink ratio of up to 3:1

SMALL-DIAMETER HEAT-SHRINK TUBING from Raychem Corp. (Menlo Park, CA) features a shrink ratio of up to 3:1, simplifying the manufacture of compact medical devices. The medical-grade Altera MicroFit tubing provides electrical insulation, mechanical protection, and strain relief for devices with diameters ranging from 0.007 to 0.045 in. The tubing's high shrink ratio eases installation because its diameter is large enough to easily slide over a microsized substrate. Yet, when heated, the tubing will shrink to fit tightly on a variety of different-sized substrates.

Altera MicroFit tubing is available in two USP Class VI­compliant materials. MT1000 is made of a tough, semirigid fluoropolymer suitable for applications requiring high-temperature autoclaving and cut-through resistance. It can be sterilized by radiation, EtO, steam, or dry heat. MT2000 is made of a tough, modified polyolefin that offers flexibility, lubricity, and good electrical insulation. Its low shrink temperature enables the tubing to shrink faster than similar materials, thereby reducing the risk of damage to temperature-sensitive substrates. The tubing can be sterilized by gamma radiation or EtO with no significant change in properties.

For more information, contact Raychem Corp. at 415/361-7840.

Desktop CNC Minimill Machines Small Medical Parts Provides fast, smooth, quiet operation

SERVO PRODUCTS CO. (Pasadena, CA) has developed a PC-driven, miniature desktop CNC milling machine that can mill, drill, engrave, and prototype small medical and dental parts. The Impact System 2 minimill features three-axis capability, 10 x 51Ž4 x 31Ž2-in. table travel, and precision-ground ball screws. An optional fourth-axis full-contouring and indexing rotary table makes it possible to machine rings and other highly contoured surfaces.

The minimill provides fast, smooth, and quiet operation. It is equipped with precision-ground ball screws for close-tolerance machining and features high-contouring and rapid traverse rates. The standard milling spindle offers infinitely variable speeds from 200 to 20,000 rpm over two speed ranges. The control provides 40-millionths resolution and closed-loop servo-drive motors. Other features include adjustable gibs for more accurate machine tolerance, an optional automatic single-shot oiling system for lubricating ways and leadscrews, and the availability of dual spindle heads for machining two parts at one time or performing sequential operations with different tools.

Standard software features include three- or four-axis simultaneous linear interpolation, circular interpolation, mirror image, cutter diameter compensation, and CAD/CAM compatibility. Any length program can be run on the system. An optional programming mode is available for operators with limited CNC programming experience.

For more information, contact Servo Products Co. at 800/521-7359.