UCD crest replicated in HDPE polymer using negatively patterned BMG mould. The overall dimensions of the crest are 10 microns x 8 microns.
You might recall as a kid - or maybe you have seen your own kids do this - working with modelling plastic or clay, squashing it into hard, patterned moulds to make imprints on the pliable material. That may be child's play, but being able to cost-effectively impress patterns into plastics reliably at a much smaller scale could offer enormous opportunities. They include being able to making devices that can quickly and cheaply analyse biological materials, perhaps looking for signs of disease or infection in a drop of blood, or picking up on contamination in a water supply.
Researchers at UCD have developed an approach using a curious type of material called bulk metallic glass, which was created in the 1970s. BMGs are neither typically metallic nor glassy, but combine the best of both materials, explains Prof Michael Gilchrist, Head of UCD School of Mechanical and Materials Engineering. "If you consider a typical metal and a glass, they are intrinsically different classes of materials," he says. "Metal has a crystalline microstructure and the size of the grains are typically within the order of about tens of microns [or thousandths of a centimetre]. But a glass material is not crystalline, it is amorphous, and the dimension limits of a crystalline material don't exist in an amorphous material."
BMGs combine the qualities of both: the mechanical properties of metal with the amorphous nature of glass, which makes it an attractive option for manufacturing processes that need to work at small dimensions. Prof Gilchrist's colleague at UCD, Dr David Browne, has developed technology to make bulk metallic glasses by alloying different materials together and casting them in 'ingots' around the size of your little finger. Together, their groups were able to make moulds from BMG onto which they micro-machined patterns. Then, when polymer material was injected into the BMG moulds, the polymer took a negative imprint of the positive pattern.
The advantages of their precision manufacturing system, which they describe in recent papers in Materials Today and in the Journal of Micromechanics and Microengineering, are that it could offer a relatively cost-effective way of mass-producing structures at those small dimensions. "The approach allows you to achieve things more specifically with greater accuracy at those dimensions. And it also allows you to manufacture commodity products for mass markets," says Prof Gilchrist. "We are hoping to use the BMG material to create polymer parts that have dimensions which allow us to develop microfluidics for 'lab-on-a-chip' devices or disposable diagnostics devices."
Conquering the challenges of creating accurate, mass-reproducible structures at such tiny levels would open up potential applications for cheaper, rapid systems to test or diagnose 'on the spot' rather than having to send samples off to labs for analysis, he adds. "Instead of a company being able to manufacture tens of thousands of expensive devices and selling those to laboratories around the world, by having the system embedded into a disposable device made using economic manufacturing technologies, you are then opening up potential markets numbering tens of millions."
The researchers are now working closely with NovaUCD to identify market opportunities for the BMG technology, and they have identified microfluidics as an important area. And Enterprise Ireland has just granted almost €500,000 to the researchers to support work with Irish industries to apply the technology to microfluidics products. While the immediate focus may be on enabling microfluidics devices for diagnostic testing, other opportunities lie down the road, notes Prof Gilchrist. "If you look at implantable medical devices that go into the body, such as new catheter tips or new ocular or neural implants, they will need to be increasingly small where the dimensions are at the submicron scale," he says. "And our technology could equally be applied to those devices."
FURTHER DETAILS IN:
Zhang, N., Byrne, C.J., Browne, D.J. & Gilchrist, M.D., Towards nano-injection moulding. Materials Today, 15 (5) pp. 216-221 (2012). Zhang, N., Chu, J.S., Byrne, C., Browne, D. & Gilchrist, M.D., Replication of micro/nano scale features by micro injection molding with Bulk Metallic Glass (BMG) mold insert. Journal of Micromechanics and Microengineering, 22 065019 (2012).
