Wu Chenjun, Omori Toshihiro, Ishikawa Takuji
Graduate School of Engineering, Tohoku University, Aramakiaza Aoba 6-6-01, Sendai, Miyagi 980-8579, Japan.
Graduate School of Biomedical Engineering, Tohoku University, Aramakiaza Aoba 6-6-01, Sendai, Miyagi 980-8579, Japan.
PNAS Nexus. 2024 Oct 15;3(10):pgae463. doi: 10.1093/pnasnexus/pgae463. eCollection 2024 Oct.
Microrobots that can move through a network of blood vessels have promising medical applications. Blood contains a high volume fraction of blood cells, so in order for a microrobot to move through the blood, it must propel itself by rearranging the surrounding blood cells. However, swimming form effective for propulsion in blood is unknown. This study shows numerically that a surface-active microrobot, such as a squirmer, is more efficient in moving through blood than an inert microrobot. This is because the surface velocity of the microrobot steers the blood cells laterally, allowing them to propel themselves into the hole they are digging. When the microrobot size is comparable to a red blood cell or when the microrobot operates under a low Capillary number, the puller microrobot swims faster than the pusher microrobot. The trend reverses under considerably smaller microrobot sizes or high Capillary number scenarios. Additionally, the swimming speed is strongly dependent on the hematocrit and magnetic torque used to control the microrobot orientation. A comparative analysis between the squirmer and Janus squirmer models underscores the extensive applicability of the squirmer model. The obtained results provide new insight into the design of microrobots propelled efficiently through blood, paving the way for innovative medical applications.
能够在血管网络中移动的微型机器人具有广阔的医学应用前景。血液中血细胞的体积分数很高，因此微型机器人要在血液中移动，就必须通过重新排列周围的血细胞来推动自身前进。然而，在血液中有效推进的游动形式尚不清楚。这项研究通过数值模拟表明，表面活性微型机器人，如蠕动器，在血液中移动比惰性微型机器人更有效。这是因为微型机器人的表面速度能使血细胞横向移动，使它们能够自行推进到它们所挖掘的空洞中。当微型机器人的尺寸与红细胞相当时，或者当微型机器人在低毛细管数下运行时，拉动式微型机器人比推动式微型机器人游动得更快。在微型机器人尺寸小得多或毛细管数高的情况下，这种趋势会逆转。此外，游动速度在很大程度上取决于血细胞比容和用于控制微型机器人方向的磁转矩。蠕动器模型和双面蠕动器模型之间的对比分析强调了蠕动器模型的广泛适用性。所获得的结果为高效推进通过血液的微型机器人的设计提供了新的见解，为创新医学应用铺平了道路。
