In medical apps, there's small and then there's small

One trend that visitors to the Medtec exhibition and conference in Stuttgart, Germany (Feb. 15 to 17) can expect to see is increased miniaturization of medical devices.

Market analysts at Frost & Sullivan (Palo Alto, CA) expect medical devices to amount to a $50-billion market with double-digit growth this year. One trend to look for at the show, organized by Modern Plastics Worldwide''s parent company, Canon Communications, is lab-on-a-chip (LOC), which essentially puts a full-scale medical laboratory onto a chip the size of a credit card, making diagnostics more mobile and faster.

Because the technological and economic risks involved in developing such devices are often too high for many companies, thinXXS GmbH (Zweibrucken, Germany) has come up with a modular microfluidic construction kit that provides a platform for assembly of up to four modules, such as pumping, micromixing, chromatography, and electrodes on a single unit.

"We imagine embedding the biochips, which are manufactured using microinjection molding or microhot embossing, in a periphery of plastics. This allows us to manufacture large numbers at low prices," says Thomas Stange, marketing director at thinXXS. With a few drops of biofluid, the LOC can provide a whole series of diagnostic results at a patient''s bedside.

Jenoptik Mikrotechnik (Jena, Germany) targets an alternative to injection molding for LOCs. "Hot embossing is gentle on the substrate and provides better-formed structures than injection molding," says Johannes Frohling, marketing/sales director. Acrylic, polycarbonate (PC), and high-heat-resistant PEEK are possible materials for the application. Dies for forming are etched into silicon or nickel or can be produced by the LIGA (deep X-ray lithograph, electroforming, and molding) process.

Frohling says the most critical step in processing is separation of the die. This is achieved by flushing it with nitrogen or air. The process can create structures down to 70 nm. It sells for up to €600,000.

thinXXS'' Stange foresees this technology ultimately providing patients with results immediately after examinations. "Thanks to new miniaturized components such as [our] MDP1304 micropump, manufacturers of medical and in vitro diagnostic devices increasingly succeed in making the heavy apparatuses from the lab [much] smaller and more mobile."

This self-priming membrane pump, about the size of a _1 coin, transports up to 6 ml of liquid/min. Since it uses a piezoceramic, rather than d-c, motor to provide the pressure, the pump consumes less than .2 W/hr. Stange says the entire unit consists of only four components: a pump head, two valves, and the actuator, which means it can be customized to regulate flow rate or back-pressure according to need. The pumps can be molded from a wide variety of polymers, Stange says, and are essential components in micromixers, which have snake-like winding channels that allow fast and effective mixing of liquids.

KNF Flodos (Sursee, Switzerland) has come up with a diaphragm pump, model NF5, that measures just 2.5 cm and weighs 32g. It is able to transport liquids or liquid-gas mixtures at flow rates of up to 50 ml/min. It offers a suction height of up to 4m.

Bartels Microtechnik (Dortmund, Germany) together with processing partner Fennel CosMed (Bad Oeynhausen, Germany) have started serial production of plastics microvalves for injection molded micropumps. Coming in eight possible designs in two sizes with different response times, these units are adaptable to pressure and flow-rate parameters. The three-layer systems from either PC/polyimide or polyetherimide/polyimide consume no energy, have a low internal volume, and are pressure resistant up to 200 bar.

Robert Colvin [email protected]

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