At a facility located in Zweibrücken on the German/French border, the company thinXXS Microtechnology has an in-house mould department that manufactures intricate disposable microfluidic devices, developed to give quick diagnostic tests for medical conditions ranging from bacterial infections to cancer cells. Producing such macroscopic parts with microstructures on a device no larger than a credit card requires high, repeatable precision and a very clean environment and this is exactly what Sumitomo (SHI) Demag has helped the facility to achieve.
Medical professionals and diagnostic laboratories from all over the world regard thinXXS as the micro-mould engineering expert. Using ultra-fine precision milling machines, the German engineering team produces moulds featuring intricate channels and microstructures that are not visible to the naked eye. Drops of fluid, such as blood, are mixed in a reservoir in the moulded clinical test devices to create a reaction, which can reveal an infection within minutes.
‘We are dealing with dimensions less than a hair’s breadth in combination with highly complex geometries,’ says Tobias Lacroix, Head of Micro Injection Moulding at thinXXS.
An all-electric Sumitomo (SHI) Demag IntElect 100-180 injection moulding machine was selected by thinXXS to manufacture the disposable bacterial quick tests. The final test device consists of three different components, all of which are produced on the IntElect in four-cavity moulds and assembled in-house.
With a shot weight of approximately 12g, two of the individual components are made from uncoloured poly methyl methacrylate, the third from blue coloured polypropylene. Accurate reproduction of surface detail, high repeatability and part tolerances in the micrometre range were all critical considerations when selecting the machine, says Lacroix. ‘Sumitomo’s well thought-out concept was the most convincing and the project timeline adhered to our tight schedule.’ In addition to installing the injection moulding machine, Sumitomo supplied the downstream handling and automation system.
The all-electric IntElect 100-180 machine manufactures all three components in an ISO Class 8 cleanroom
Behind closed doors
To prevent particles of dust and other contaminants entering the production process, the machine operates in an ISO Class 8 cleanroom environment.
A six-axis articulated robot removes finished test components from the four-cavity mould, placing them onto a small load carrierIt can be observed only through a glass window in the cleanroom cabin. As an added safeguard, the entire cleanroom cell is fully enclosed in an ISO Class 7 containment area. A six-axis Stäubli articulated arm robot removes the finished test components from the four-cavity mould and places them onto a small load carrier. When the carrier is full, these are transported on a conveyor to the assembly and packing hall. Here, thinXXS staff members wear protective masks and clothing to maintain the Class 7 cleanroom conditions and assemble the components into the finished test devices.
With an L/D ratio of 20 and a clamping force of 1,000kN, the IntElect produces the device’s components within 16 seconds. The injection moulding process involves dispensing dried pellets into the IntElect’s plasticisation unit via the feeder and metering unit. The mould is then heated using water to 90°C. A temperature control device is connected to the injection moulding machine via a controller area network (CAN) Bus interface, and the controllable activeLock non-return function ensures that no melt flows back into the screw channels after the injection phase has started.
At the end of the process, thinXXS staff assemble and package the medical test devices in ISO Class 7 cleanroom conditions
Each phase of the moulding process is designed to maintain the highest precision to accommodate the quick test’s fluidic functional design, says Lacroix. ‘Only a highly accurate part can guarantee a 100% reliable diagnostic result. We expected our injection moulding machine to achieve an extremely accurate reproduction of surface detail, a high repeatability and part tolerances in the micrometre range.’
Happy with the overall outcome, Lacroix says that the complete system is operating with precision and repeatability: ‘Sumitomo fully supported us during the GMP validation and we passed the assessment without problems. It was particularly helpful that our contacts looked after all technical and administrative matters concerning the complete line.’