Mirzaee-Kakhki Mahla, Ernst Adrian, de Las Heras Daniel, Urbaniak Maciej, Stobiecki Feliks, Tomita Andreea, Huhnstock Rico, Koch Iris, Ehresmann Arno, Holzinger Dennis, Fischer Thomas M
University of Bayreuth, Physics, Universitätsstr. 30, 95447 Bayreuth, Germany.
Institute of Molecular Physics, Polish Academy of Sciences, ul. M. Smoluchowskiego 17, 60-179 Poznań, Poland.
Soft Matter. 2021 Feb 19;17(6):1663-1674. doi: 10.1039/d0sm01670e.
Paramagnetic colloidal spheres assemble to colloidal bipeds of various length in an external magnetic field. When the bipeds reside above a magnetic pattern and we modulate the direction of the external magnetic field, the rods perform topologically distinct classes of protected motion above the pattern. The topological protection allows each class to be robust against small continuous deformations of the driving loop of the external field. We observe motion of the rod from a passive central sliding and rolling motion for short bipeds toward a walking motion with both ends of the rod alternately touching down on the pattern for long bipeds. The change of character of the motion occurs in form of discrete topological transitions. The topological protection makes walking a form of motion robust against the breaking of the non symmorphic symmetry. In patterns with non symmorphic symmetry walking is reversible. In symmorphic patterns lacking a glide plane the walking can be irreversible or reversible involving or not involving ratchet jumps. Using different gauges allows us to unravel the active and passive aspects of the topological walks.
顺磁胶体球在外部磁场中组装成各种长度的胶体双足结构。当双足结构位于磁性图案上方且我们调制外部磁场的方向时，这些杆状物在图案上方执行拓扑上不同类别的受保护运动。拓扑保护使得每一类运动对于外部场驱动回路的小连续变形具有鲁棒性。我们观察到，短双足结构的杆状物呈现从被动的中心滑动和滚动运动，到长双足结构的杆状物两端交替触地的行走运动。运动特征的变化以离散拓扑转变的形式出现。拓扑保护使行走成为一种对非对称对称破缺具有鲁棒性的运动形式。在具有非对称对称的图案中，行走是可逆的。在缺乏滑移面的对称图案中，行走可以是不可逆的，也可以是可逆的，这涉及或不涉及棘轮跳跃。使用不同的规范使我们能够揭示拓扑行走的主动和被动方面。
