Data from: Symmetry-breaking phase transitions in highly concentrated semen

New experimental evidence of self-motion of a confined active suspension is presented. Depositing fresh semen sample in an annular shaped microfluidic chip leads to a spontaneous vortex state of the fluid at sufficiently large sperm concentration. The rotation occurs unpredictably clockwise or counterclockwise and is robust and stable. Furthermore, for highly active and concentrated semen, richer dynamics can occur such as self-sustained or damped rotation oscillations. Experimental results obtained with systematic dilution provide a clear evidence of a phase transition towards collective motion associated with local alignment of spermatozoa akin to the Vicsek model. A macroscopic theory based on previously derived self-organized hydrodynamics models is adapted to this context and provides predictions consistent with the observed stationary motion.

本研究呈现了受限活性悬浮体系（confined active suspension）自运动的全新实验证据。将新鲜精液样本注入环形微流控芯片（microfluidic chip）中，当精子浓度足够高时，流体会自发形成涡旋状态。该涡旋的旋转方向随机，可呈顺时针或逆时针，且状态稳健稳定。此外，针对高活性高浓度的精液，还可观测到更为丰富的动力学行为，例如自持旋转振荡或阻尼旋转振荡。通过系统性稀释实验获得的结果，清晰证明了存在朝向集体运动的相变，该相变与精子（spermatozoa）的局部对齐行为相关，其机制类似于维切克模型（Vicsek model）。基于已有自组织流体动力学模型推导得到的宏观理论，经适配本研究场景后，所给出的预测与观测到的稳态运动结果一致。