Open AccessSwimming Back and Forth Using Planar Flagellar Propulsion at Low Reynolds Numbers
Author(s) -
Khalil Islam S. M.,
Tabak Ahmet Fatih,
Hamed Youssef,
Mitwally Mohamed E.,
Tawakol Mohamed,
Klingner Anke,
Sitti Metin
Publication year - 2018
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.201700461
Subject(s) - propulsion , flagellum , physics , planar , reynolds number , perpendicular , magnetic field , bundle , mechanics , acoustics , geometry , computer science , materials science , mathematics , biology , biochemistry , computer graphics (images) , quantum mechanics , turbulence , composite material , gene , thermodynamics
Abstract Peritrichously flagellated Escherichia coli swim back and forth by wrapping their flagella together in a helical bundle. However, other monotrichous bacteria cannot swim back and forth with a single flagellum and planar wave propagation. Quantifying this observation, a magnetically driven soft two‐tailed microrobot capable of reversing its swimming direction without making a U‐turn trajectory or actively modifying the direction of wave propagation is designed and developed. The microrobot contains magnetic microparticles within the polymer matrix of its head and consists of two collinear, unequal, and opposite ultrathin tails. It is driven and steered using a uniform magnetic field along the direction of motion with a sinusoidally varying orthogonal component. Distinct reversal frequencies that enable selective and independent excitation of the first or the second tail of the microrobot based on their tail length ratio are found. While the first tail provides a propulsive force below one of the reversal frequencies, the second is almost passive, and the net propulsive force achieves flagellated motion along one direction. On the other hand, the second tail achieves flagellated propulsion along the opposite direction above the reversal frequency.