“…The swimming of single bacteria and the collective motion of microorganisms have attracted the interest of a varied community. Accumulation at interface (both solid–liquid and air–liquid) was studied with a number of theoretical (Ishimoto & Gaffney, ), computational (Costanzo, Di Leonardo, Ruocco, & Angelani, ; Mathijssen, Doostmohammadi, Yeomans, and Shendruk, ; Theers, Westphal, Gompper, & Winkler, ), and experimental approaches (Wioland, Lushi, & Goldstein, ), and several puzzling phenomena such as upstream flowing (Mathijssen, Shendruk, Doostmohammadi, Yeomans ) and oscillatory motion in microchannel (de Graaf et al., ) emerged when bacteria swim under strong confinement. The interaction of flagellated microswimmers with structured surfaces often results in swimmer trapping as shown in Sipos, Nagy, Di Leonardo, & Galajda () for convex wall and in Gu et al.…”