Medical Device Link.

Originally Published EMDM September 2003

Product Update

A micropump developed by thinXXS Microtechnology relies on a platform technology to speed product development and optimize production.

Innovative miniature pumps and valves that open under very low pressure are highlighted.

Flexibility and surprising affordability are among the features of two recently introduced micropumps. A platform architecture developed by thinXXS Microtechnology (Mainz, Germany) is at the heart of its malleable pump. Minor design revisions can result in dramatic changes in performance, according to the firm. For its part, Bartels Mikrotechnik (Dortmund, Germany) has unveiled a moulded miniature pump suited for serial production. Its low cost makes it feasible for use in disposable products, claims the company. Across the pond, US-based Resenex Corp. has developed a one-way valve with a proprietary disc design. This innovation allows the valve to operate at very low pressure.

What Lies Beneath

What is truly revolutionary about the MDP1304 micropump, says thinXXS marketing manager Thomas Stange, lies beneath the surface. “From the outside, it looks very similar to our previous model. But we have engineered a number of changes inside the pump, the most important of which is the use of a platform concept,” says Stange. The resulting flexibility, he adds, “helps to speed product development and integration, and reduces production costs.”

The platform technology brings flexibility to the product range, says Stange. “Simply by changing the actuator or membrane, for example, we can engineer a pump with different performance parameters.” For that reason, he adds, the MDP1304 pump should really be seen in an evaluative context. In fact, the company offers an evaluation kit for the plastic pump that includes a pump controller and ac/dc convertor.

The MPK0204 evaluation kit allows first-time users to take the micropump on a test drive. The entire system is operational within minutes, and the control unit allows the user to vary the pump’s flow rate by using the internal frequency generator or via a PC.

The pump can be quickly and easily adapted to suit user requirements. “The customer just needs to tell us what he wants in terms of overall dimensions, flow rate, back pressure, shape, and material properties, and the platform technology will allow us to quickly create an appropriate micropump.”

Device OEMs have shown an interest in the technology, says Stange, who cites promising developments in microfluidic and analytical applications.

Low-Cost Pump Suited for Disposables

Traditionally, micropumps have been based on silicon technology, making their cost prohibitive for many applications. Bartels Mikrotechnik has developed a plastic pump no larger than a sugar cube that is affordable enough to be used in disposable devices, according to managing director Frank Bartels.

“Our goal at the development stage was to keep the pump design as simple as possible,” says Bartels. For example, the actuator is a piezoceramic element attached to a plastic membrane. The membrane covers a small pump chamber that is fed by dual valves; flow control can be adjusted by turning a knob on the pump evaluation kit or by means of a USB-connected device.

Measuring 1 mm in height and 12 mm diam, the Micropump mP5 oem has an adjustable flow rate of 50 nl/min to 5 ml/min. PC/PI or PPSU/PI materials can be used for the parts that come in contact with the pump media. The product is suited for a range of microfluidic applications in the medical technology, pharmaceutical, analytical, and biotechnology sectors.

Bartels Mikrotechnik plans to begin volume production of the pump by the end of this year.

Valves Come Armed and Ready

One-way valves developed by Resenex Corp. (Chatsworth, CA, USA) feature an internal disc with a proprietary design. This innovation allows the valves to open at very low pressure.

“What makes these valves unique are the four little arms that are attached to the disc,” says general manager Carlos Guerrero. When liquid or air flows through the valve, the arms stretch out, opening up the disc and the valve itself. When the flow stops, the arms retract, and push back the disc. “They act as a spring, setting the valve down to a close position,” he says.

The disc is made of silicone, a material that enables very low opening pressures. “For high-pressure applications, we have also used higher-grade silicone, which is a thicker material that requires more pressure to open the check valve,” Guerrero adds. “EPDM has also been used for an application that involved a certain kind of liquid that might affect silicone.” The disc is placed in an acrylic housing consisting of a seat and cover that are welded together.

The valves undergo 100% testing. “We make sure to test them with air,” says Guerrero. “We have noticed that, even if we have rejections with air testing, the valve usually passes liquid testing. However, we still reject those parts to ensure that they are safe for every application.”

Shielded Connectors

The company also offers large-bore shielded connectors. “The distinctive characteristic of our connectors is that both the female and male parts have a protective shield,” says Guerrero. “This means that neither the user nor the patient are going to be contaminated by the transferred fluids in the connector, which is essential when handling biological liquids.” All the connectors seal without O-rings and feature large bores for high flow rates. “Our barbed fittings allow assembly without adhesives, and they feature a rotating outer shield that prevents the tubing from twisting,” Guerrero adds.

Resenex has strict in-house quality control standards. “We inspect every individual batch of products before it ships out,” says Guerrero. “We also maintain close relationships with our suppliers to ensure that all products are of the highest quality.”

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