We examine experimentally the deformation of flexible, microscale helicalribbons with nanoscale thickness subject to viscous flow in a microfluidicchannel. Two aspects of flexible microhelices are quantified: the overall shapeof the helix and the viscous frictional properties. The frictional coefficientsdetermined by our experiments are consistent with calculated values in thecontext of resistive force theory. Deformation of helices by viscous flow iswell-described by non-linear finite extensibility. Under distributed loading,the pitch distribution is non-uniform and from this, we identify both linearand non-linear behavior along the contour length of a single helix. Moreover,flexible helices are found to display reversible global to local helicaltransitions at high flow rate.
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