Droplet microfluidics is a recent trend of laboratory automation technologies, which allow scientists to explore the biological world at an unprecedented resolution and throughput. The new infrastructure is powered by innovative instrumentation, software as well as the consumable reagents and chips. In this context, plastic chips play a key role in enabling these applications, as they ensure a consistent and scalable droplet production.
What are the microfluidic chips?
At the foundations of droplet microfluidics
are the chips used for high-speed droplet generation, injection, splitting, merging, mixing and storing. However, specialist injection moulding knowledge is required for producing chip features with micrometer resolution. Material science expertise is equally important as chosen plastics need to be compatible with fluorinated oils and biological analysis workflows. Finally, mechanical design is also important, as plastic chips feature a combination of microscopic features defining microfluidic functions, in addition to the macroscopic chip features like snap fits for assembly and liquid containers (wells).
High volume chips’ molding
When microfluidic channels are tested and confirmed for the desired research objective, higher volume of the chips may be demanded and this is where Micromolds company with micro injection moulding steps in.
Not only does injection moulding come handy because of its high productivity but also because it enables the possibility to make non-micro structures – like the reservoirs, wells, inlet and outlet gates together with micro geometries in one single moldable piece. However, this comes at a certain cost which is challenging for any injection molding professional.
When things get really small, regular machining might not be an option even though theoretical machine and tool precision would let do so. For such micro tools we had to use tool inserts that are located inside the mold base. Since the high plastic injection pressures forces are exerted inside the mold cavity and core, we had to experiment a lot with different machining options of those inserts – from laser ablation to multiphoton polymerization.
Manufacturing the insert is just one side of a coin, the most challenging task was to locate the insert inside the mold base so that alignment of the core and cavity would be perfect and the clamping forces would not brake the inserts.
Extremely flat surface of the chip was needed to make micro geometries possible. This meant that any sink marks caused by the uneven wall thickness had to be solved. However, we could not make walls thinner than the smallest ejectors we had since this would have caused us demolding problems. In fact, it did. At the first trials the ejectors were too weak and started to bend.
As a way out we had to play with injection parameters to reduce the sink marks to the minimum so the wall thickness could remain unchanged and thus thicker ejectors could be used.
We are excited to participate in the development and production of droplet microfluidic tools for the life science sector. We constantly grow with our customers by pushing together on the technical limits of plastic chip designs and enabling new applications, which finally contribute to modern biological research and human health.