Shear Stress-Triggered Deformation of Microparticles in a Tapered Microchannel

We demonstrate that it is possible to produce microparticles with high deformability while maintaining a high effective volume. For significant particle deformation, a particle must have a void region. The void fraction of the particle allows its deformation under shear stress. Owing to the importance of the void fraction in particle deformation, we defined an effective volume index (V*) that indicates the ratio of the particle's total volume to the volumes of the void and material structures. We chose polyethylene glycol diacrylate (Mn similar to 700) for the fabrication of the microparticles and focused on the design of the particles rather than the intrinsic softness of the material (E). We fabricated microparticles with four distinct shapes: discotic, ring, horseshoe, and spiral, with various effective volume indexes. The microparticles were subjected to shear stress as they were pushed through a tapered microfluidic channel to measure their deformability. The deformation ratio R was introduced as R = 1-W-deformed/D-original to compare the deformability of the microparticles. We measured the deformation ratio by increasing the applied pressure. The spiral-shaped microparticles showed a higher deformation ratio (0.901) than those of the other microparticles at the same effective volume index.

Automated summary

The study demonstrates the production of microparticles with high deformability and effective volume while emphasizing the importance of void fraction in particle deformation. A new effective volume index (V*) is defined to indicate the ratio of a particle's total volume to void and material structures. Spiral-shaped microparticles exhibit higher deformation ratios compared to other shapes at the same effective volume index.