Technology news
MATERIALS
Porous PTFE Material Withstands Conventional Machining
A fully fluorinated polymer that resists a wide range of aggressive chemical media, PTFE is used in medical devices where properties such as a low coefficient of friction, temperature resistance, and the preservation of mechanical properties under harsh conditions are desirable. PTFE membranes and loosely pressed, partially sintered products, however, generally don't maintain their physical integrity when being machined. The process tends to result in collapsed pores and crumbled edges. FluoroLogic LLC (Los Alamitos, CA, USA) has developed a porous PTFE that can be machined by means of conventional equipment without having to settle for those trade-offs. The fully compressed and sintered material is suited for the manufacture of intricate components that must meet tight tolerances. Typical applications include filtration, chromatography, and sample-preparation instruments.
While the machinability of the material is its most unique characteristic, the company's ability to achieve precisely controlled pore sizes and uniform pore distribution has also been a strong selling point. A current project at FluoroLogic involves the manufacture of a pump component. "We are providing the inlet and outlet filter for a pump that will be part of an over-the-counter medical-related product," says company partner Sergio R. Salas. "The client was impressed by our ability to tailor the pore diameter and volume of the Teflon filter to meet the airflow requirements."
FluoroLogic can supply porous PTFE with customer-specified pore sizes and porosity levels in sheet, billet, rod, and film, as well as in finished component geometries. Lot traceability is ensured from incoming resin to finished product.
For more information, contact FluoroLogic LLC, 10439 Los Alamitos Blvd., Los Alamitos, CA 90720, USA; phone: +1 526 6269111; fax: +1 562 6269171; e-mail: fluorologic@hotmail.com.
SURFACE TREATMENT
Coating Process Enhances PTCA Stylet's Torque and Lubricity
A PTFE-coated wire designed for use as a percutaneous transluminal coronary angioplasty (PTCA) stylet features one-to-one torque, an absence of whipping, and gliding properties that enable easy insertion. Developed by MCTec (Venlo, Netherlands), the stylet was introduced at the recent MEDTEC exhibition and conference in Amsterdam.
The combination of properties is a result of the entire manufacturing process, according to technical director Hans Hanssen, but the coating application method is a particularly critical factor. "The stress relief, the coating itself, and the grinding all play a role in achieving the desired characteristics of the product, but we clearly benefit from the emulsion process we use to apply the coating instead of the conventional spraying technique.
"The problem with spray coating is that it does not give you smoothness and it is not consistently applied," says Hanssen. The emulsion process, he adds, enables the production of uniform diameters because the layer thickness can be precisely controlled. It is also beneficial from an environmental perspective because it results in less waste.
The precoated and ground wire can be supplied in various colours, lengths, and substrates. The wire is also available with a hydrophilic coating.
MCTec is a recently launched joint venture of Belden Wire & Cable (Venlo, Netherlands) and Biomat (Maastricht, Netherlands), part of a holding company controlled by the University of Maastricht. The university's involvement has been a tremendous asset for the start-up company, says Hanssen. "Through Biomat, we have direct access to the school of medicine and the university hospital," he says. "This allows us to draw on substantial R&D resources and to get direct feedback from the products' potential end-users."
LAB SERVICES
Contract Laboratory Develops Surface Tests for Medical Devices
An analytical service lab has developed and made available more than 30 atomic force microscopy (AFM) tests that can be used to analyze the properties of materials used in medical devices. Biometrology Inc. (Alameda, CA, USA) specializes in high-precision, in situ surface measurements performed in fluid environments. Material development and surface treatment are among the applications that stand to benefit from AFM testing.
A successor to scanning electron microscopy (SEM), AFM is a high-resolution, low-force imaging technique that can produce 3-D images down to the atomic scale. Developed by IBM scientists in Rushlikon, Switzerland, AFM uses a scanning probe that senses forces in the piconewton range. "AFM can produce measurements up to 10 µm in height and 200 µm in the x and y planes and growing," says Michael Allen, president of Biometrology. Unlike SEM, the technique does not require that the probe or the sample conduct electricity. "The real advantage of AFM," adds Allen, "is that it can be used in fluid environments, which are more relevant to medical and biochemical applications. It is the most advanced technology available for studying solid-liquid interfaces." A further advantage of the technique is that measurements can be performed in a noncontact mode, which reduces the risk of damaging soft surfaces in a sample.
Biometrology was formed in June 1999, and performs a range of tests for R&D and quality control purposes. Tests and evaluations include adhesion, adsorption, corrosion, ex situ wear, width and height, particle size, pore diameter, process monitoring, surface defects, and topographic imaging. Samples that can be analyzed include medical devices, micromachined materials, organic films, coatings, colloids, drug-delivery materials, and filtration media. The firm offers an Internet delivery subsystem that allows clients to view and download their lab results over password-secure Web sites.
According to Allen, the use of AFM as a metrology tool is growing steadily. "As we enter an age of nanotechnology, AFM is becoming an increasingly important technique in surface analysis," he says.
