Glow discharge cleaned copper grid

For TEM imaging, structures were stained using a 1% Uranyl acetate solution and imaged on a FEI Tecnai G2 Spirit electron microscope. For each preparation, 6–8 μl of 1 nM DNA origami sample was wicked onto a glow-discharge-cleaned copper grid (Electron Microscopy Sciences, Hatfield, PA) and incubated for 5–10 min. The sample solution was then removed carefully with Whatman #4 filter paper and the grids were immediately stained with two 6 μl drops of 1% Uranyl acetate solution. Grids were dried for at least 10 min before imaging. TEM images were analyzed by ImageJ to try to quantify the length of the gap between the two barrels to determine if the L6 + L3 + L1 had a smaller gap at zero force than the other devices. However, the angular distribution prevented the quantification of the gap length (Supplementary Fig. S19).