Compliance switching for adhesion control

Abstract

Climbing lizards display numerous advanced features in their locomotion, notably a method to quickly switch between a state of low and high adhesive force capacity. Inspired by the gecko's adhesive switching, a method of mechanically switching between low and high adhesive states is reported. In particular, the first switching of an adhesive system using only a change in system compliance is demonstrated. Mechanical clamping and a novel magnetic clamping system are used to switch an iron/PDMS composite adhesive between a soft and rigid state. The switch in compliance directly influences the maximum load of the adhesive as meas-ured in lap-shear. Notably, contact area and the contact chemistry remain unaltered despite significant changes in force capacity. The demonstration of a compliance-only switching mechanism has broad implications for understanding natural adhesive systems-especially in organisms that can dynamically alter their rigidity (e.g. cells).

Switchable Adhesives for Multifunctional Interfaces

“…[105] Gillies et al fabricated a magneto-elastomer composite with surface microridges. [99] Additionally, using magnetic fields can change the stiffness of a backing layer under normal adhesion, increasing and decreasing adhesion by ≈10%. [159] Micropillars can also be loaded with magnetic particles which can reorient from tip to side contact during the application of a magnetic field, reducing contact area, and resulting in an adhesion change of SR ∼ 15.…”

“…As such, it is a viable target for designing a switchable adhesive. [99][100][101][102] For example, a system with a low modulus will release more easily than a system with high modulus, a feat that can be accomplished with a temperature sensitive material. Kim et al give a particularly clear example of a thermally triggered compliance switch.…”

“…[161] Another approach by Risan et al utilized magnetic clamps to modify the compliance of the free end of a lap shear joint to change adhesive force by 25%. [99] Additionally, using magnetic fields can change the stiffness of a backing layer under normal adhesion, increasing and decreasing adhesion by ≈10%. [91]…”

Understanding Surface Adhesion in Nature: A Peeling Model

“…Whereas geckos peel the spatulas off easily due to the low adhesion/friction by rolling the toes upward and backward (Figure 7 b). [ 93,138 ]…”

“…Reproduced with permission. [ 138 ] c,d) Infl uence of the pulling angle ( θ ) on the ''normal adhesive force'' ( F n ) and ''lateral frictional force'' ( F L ), including the contributions of the van der Waals force ( F vdW ) and friction force ( F f ) to F n and F L . Reproduced with permission.…”