Enhanced flagellar transport in asymmetric periodic arrays

Abstract

Active swimmers are ubiquitous in nature, found in many diverse biological systems ranging from bacteria to vertebrate fish. Of particular importance are sperm cells which are swimmers that are crucial for the survival of many species including humans. Despite decades of work, the fluid physics of sperm in complex micro-environments such as the cervical tract, or the microfluidic devices used in assistive reproductive technologies remains illusive. Recently, a novel microfluidic device featuring periodic post arrays has been developed, and shown to select sperm cells with better motility, morphology and DNA integrity, more efficiently than existing approaches. Motivated by this, here we present a multi-scale model that aims to provide insight physical insight into the motility behavior of sperm in such periodic geometries. Our model combines a fluctuating hydrodynamic model of sperm with a probabilistic discrete-time lattice approach, and we show how hydrodynamic and boundary interactions facilitate both the enhancement of speed and persistence length of sperm cells in this post array. We then discuss how this enhancement of flagellar transport is related to its propensity, and develop a phase diagram. Our findings not only shed light into the fluid physics of flagellar swimmers in periodic arrays, but also have direct implications in a broad range of areas beyond fertility, including bio-inspired robotics, disease detection and drug delivery.