DLD pillar shape design for efficient separation of spherical and non-spherical bioparticles.

Particle sorting methods in microfluidic platforms are gaining momentum for various biomedical applications. Bioparticles are found in different shapes and sizes. However, conventional separation techniques are mainly designed for separation of spherical particles. Thus, there is a need to develop new methods for effective separation of spherical and non-spherical bioparticles for various applications. Deterministic lateral displacement (DLD) microfluidic methods have become popular for high separation resolution, simplicity, and predictability. However, shape sorting in the DLD separation methods is not well researched. Recently, we explored this area and found that pillar shapes in DLD significantly affect bioparticle separation. In this work, we designed a group of different pillar shapes with protrusions and groove structures with the hypothesis that pillar protrusions will induce particle rotation while pillar grooves will confine the particle rotational movement in a directed path for effective separation in a DLD pillar array. Using combinations of protrusions and grooves, 3-dimensional spherical particles, 2-dimensional planar disc-shaped red blood cells and 1-dimensional rod-shaped bacteria were separated and two interesting phenomena were observed. Firstly, the arrangement of pillar protrusions and grooves induces inertial movements, enhancing the separation of spherical particles. Secondly, non-spherical particles experience dominant rotational movements due to the protrusions and grooves which help in changing their orientations. This gives an opportunity to perform efficient separation based on the desired orientation (the longest dimension of the particles) by restricting or containing their movement within a specific DLD path.