Technology suitable for small quantity production
In this case it is necessary to machine the inverted features in a material that is easy to dissolve (Al7075 or Al6063), and then produce the mould by depositing nickel or copper on the surface until a suitable thickness has been reached. Since the metals or alloys grown by electroforming are deposited at relatively low temperatures, they tend to be very fine grained. The very fine-grained materials (good sulphamate nickel has a grain size between 70-80 nm) will re-crystallize when exposed to higher temperatures during hot-embossing or injection moulding. Recrystallisation will lead to an increase in grain size and a corresponding decrease in hardness. The influence of recrystallisation on the side-wall roughness in a microfluidic system is in most cases insignificant, but for replication of optical components the increase in roughness can be damaging to the performance.