Micro Fluidic Moulding

Tooling Design

Creating the nickel or steel inserts with microscale features utilizes photo lithography or electro forming rather than conventional milling. These inserts must withstand the repetitive thermal cycling and high pressures required to force the melt into the sub micron grooves. Proper venting is a critical requirement in this process, as trapped air will prevent complete filling of the fine channels and cause structural defects.

Vacuum venting systems evacuate the cavity before the melt arrives, which avoids the need for excessive injection pressures.

Material Selection

Amorphous polymers with high flow rates and low birefringence are the preferred raw materials for these intricate microfluidic applications. Cyclic olefin copolymer and polycarbonate provide the optical clarity and dimensional stability required for diagnostic reading systems. Sourcing resins with high purity is critical because any contamination can block the micro channels or interfere with the chemical reactions on the chip.

Virgin resins are used almost exclusively in this field, as regrind introduces variations in flow behavior that compromise the microscale features.

Defect Prevention

Monitoring the replication rate of the microstructures involves periodic optical inspections of the moulded parts. Insufficient melt temperature can lead to incomplete replication, where the channel depths do not meet the specified dimensions. In contrast, excessive melt temperature causes thermal degradation of the polymer and increases the risk of part distortion during ejection.

Implementing dynamic mould temperature control helps balance these issues by heating the tool before injection and cooling it rapidly before ejection.