Performance and Optimisation of Microfluidic Channels with Acute Angles and Serpentine Curvatures

This study presents the measurement of fluid fields of microfluidic channels with acute angle bends between 15° and 90° and examines the influence of both angle and geometric design on these bends through simulation and experimentation. Additionally, serpentine microchannels of different radii have been explored and their corresponding fluid fields. It was found that smaller angles cause significant destabilisation of the fluid field with rapid deceleration around bends with sharp internal and external points. Constant pressure regions were found at the bends which developed into rapid pressure changes in each of the inlet and outlet channels to the corners. 3D printed test structures revealed that a core issue of small angle bends was air bubble development during filling. Effective methods to eliminate this bubble were the rounding of inner and outer points, chamfering the outer point to reduce surface area and performing a much slower filling procedure to allow air to be pushed out prior to liquid filling. Rounding of the inner and outer corners led to the highest amount of flow continuity around 45° bends while the 15° corner still had significant flow instability. The serpentine channels were found to have no flow instability due to a constant pressure gradient through all the channels. A method of instigating higher fluid instability within serpentine microchannels was found by increasing the diameter at the bend apexes to distribute the fluid. Sharp angle bends and the redesigned serpentine channel have potential for highly compact and effective designs of micromixers.