(Color online) (a) Scanning electron (SEM) micrograph of a nano-cheese-cutter at one end of an AFM cantilever. (b) SEM micrograph of an overhanging freestanding fiber on mica substrate. (c) Schematic of the contact between two fibers arranged in a crossed-cylinder geometry. (d) In the presence of external tension, the cheese-cutter (top) deforms into V-shape and the overhanging fiber (bottom) an inverted V-shape.
(Color online) (a) Typical force-displacement measurement showing paths of loading (ABC) and unloading (CDGHJK). Here d 1 = 109 ± 16 nm and l 1 = 91 ± 4.8 μm, and d 2 = 580 ± 20 nm and l 2 = 97 ± 5 μm. (b) Force curve along path BC for several sample fibers and curve fit. Only every other fifth data point is shown for clarity.
(Color online) (a) Force measurements of the same fiber on AFM cantilever (d 1 = 109 ± 16 nm and l 1 = 91 ± 4.8 μm) adhering to fibers on mica with d 2 and l 2 indicated. (b) Pull-off force as a function of mica fiber diameter. Circles are data from first fiber on AFM (cf. Fig. 3(a)) and triangle from second fiber on AFM (cf. Fig. 4(a)). Dashed curve shows the DMT prediction based on d 1 = 109 ± 16 nm and γ = 71.0 ± 13.3 mJ · m−2.
(Color online) (a) Loading-unloading cycles performed by fibers with d 1 = 140 ± 13 nm and l 1 = 42.73 ± 0.27 μm, and d 2 = 241 ± 36 nm and l 2 = 36.66 ± 0.04 μm. (b) “Pull-off” force as a function of loading cycles. Adhesion energy deduced from F* measured in the first 5 cycles is γ = 62.9 ± 10.7 mJ · m−2 (dashed line).
(Color online) Schematic of a freestanding fiber loaded at the midpoint for several central displacements.
(Color online) (a) Normalized deformed profiles for fiber tension β = 0, 7, 20, and the stretching limit β → ∞ (dashed curve). Note that the slope at x = 0 is always zero, but approaches a constant only in the limit when the profile becomes linear. (b) The constitutive relation ϕ(ω0), and the bending and stretching limits (dashed lines). Bending dominates at small ω0, while stretching prevails at large ω0. (c) Gradient of the constitutive relation as a function of vertical displacement, n(ω0).
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