Design Chain – Micro-medical parts, perfectly formed

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The use of micro- and even nano-moulding is becoming more widespread in the medical world, especially in the already-demanding field of medical devices.

Injection moulding techniques can now create tiny parts - or imbue normal-sized parts with intricate surface detail. There is little doubt that the medical industry is the main beneficiary of these new methods.

All types of parts, from hearing aids to micro-fluidic devices, are already being made in this way.

"Control of cell fate has many important implications as a means to provide cell therapy in the medical field," he said.

Injection moulding machinery maker Desma, in collaboration with KUZ Leipzig, has developed an improved way to make micro-parts from two-component liquid silicone. It says the main uses of the technique will be in the medical industry.

While the material can be used to make more effective parts, it can be difficult to process. A machine to make these parts needs a metering system for feeding and mixing, an injection moulding unit with plasticising unit, heated mould and handling equipment.

"For micro-injection, the screw diameter limits the precision, and the technique requires a large gate - resulting in a lot of waste and long cycle times," said Desma's Bjoern Dormann, in a presentation at Antec.

Desma has optimised its FormicaPlast machine to allow more accurate production of two-component silicone parts.

Firstly, it uses the plunger principle for injection, to give high precision and smooth material handling. At the same time, a transfer index mechanism is used to mould and inject the material.

"For optical microparts in particular, the melting of the thermoplastic is essential," he said.

In this process, the weight of the sprue is much more than the part itself. But using parallel injection units keeps the weight of the sprue to a minimum.

The main aim in the medical industry is to use minimally invasive surgery to implant the micro part into the body. An example is to make micro channels, which transport fluids in order to relieve pain for patients. Another high value application is micro containers. These are filled with medicine, which is then fed by a micro pump into the body. After emptying, the containers can be refilled.

Silicone lenses are another possible application of two component liquid silicone micro-moulding.

So whether micro moulding is used to make tiny parts, or to add intricate detail to the surface of conventional parts, it seems likely that its role will be increasingly important in the medical sector.  

Check out in the coming weeks for further Design Chain features and click here for the digital version of the new supplement.