Microscopy chambers were prepared from two sandwiched silanised glass coverslips (18 and 24 mm, Marienfield High Precision) attached through parafilm strips (heated for 15–20 s at 60°C and gently pressed together) to form ~2.5 mm wide parallel flow channels. Prior to the chamber assembly, the coverslips were extensively cleaned in “piranha” solution (consisting of one part 30% hydrogen peroxide and 2.5 parts 95–97% sulfuric acid) and silanised with 200 μl dichlorodimethylsilane mixed in 350 ml trichloroethylene. To immobilise the microtubules at the glass surface, the flow channels of the microscopy chambers were incubated for 5 min with 30 μg/ml monoclonal anti‐β‐tubulin (TUBB) antibody (Sigma‐Aldrich T7816; Roach et al, 1998 (link)) at room temperature. The glass surface was subsequently blocked with 1% Pluronic‐F127 in PBS for at least 30 min before use.