Bioinspired Dry Adhesives for Highly Adaptable and Stable Manipulating Irregular Objects under Vibration

Abstract

For dry adhesive-based operation, highly adaptable and stable manipulation is important but also challenging, especially for irregular objects with complex surface (such as abrupt profile and acute projection) under vibration-inducing environments. Here, a multi-scale adhesive structure, with mechanically isolated energy-absorbing backing, based on the synergistic action of microscale contact end (seta), mesoscale supporting layer (lamella), and macroscopic backing (muscle tissues) of gecko's sole, is proposed. Top layer of mushroom-like micro tips provides dry adhesion via mimicking gecko's seta, and bottom layer of physical cuts and porous feature achieves the interfacial mechanical decoupling and crack inhibition via mimicking the non-continuous distributing of lamella and compliance of muscle. The proposed dry adhesive exhibits excellent adaptable adhesion to various objects with curved or irregular surfaces, even for that with abrupt contours, as well as an amazing stable anti-vibration ability, opening a new avenue for the development of dry adhesive-based device or system.

Keywords: bioinspired adhesive materials; contact adaptability; irregular surfaces; multi-scale bionics; stable adhesion.

Figure 1

Design of MIEA‐DA. a) Structural morphology of the soles of gecko's sole; b) the structural description of the MIEA‐DA; c) the adaptability of MIEA‐DA to different objects with abrupt contours; and d) performance of MIEA‐DA under a simulate vibration environment.

Figure 2

The normal adhesion strength of different adhesives to convex and concave surfaces. a) The structural form of ODA, MI‐DA, and MIEA‐DA; b) the load–pull curves of a cylindrical probe with a radius of 20 mm to three structures; c) the normal adhesion of three structures to the cylindrical probe (R = 20 mm) under different preloads; d) the normal adhesion strength of different structures to cylindrical probes with different radii; e) The load–pull curves of a concave probe with a radius of 30 mm to three structures; f) the normal adhesion of three structures to concave probe (R = 30 mm) under different preloads; and g) the normal adhesion strength of different structures to concave probes with different radii.

Figure 3

The simulation results of adhesion on a curved surface. a) The numerical simulation results of the whole process of normal adhesion of three structures to a spherical surface; b) the contact area of three structures to a spherical surface during the loading stage; c) the changes in the damage energy of three structures during the whole process; d) the changes in strain energy with respect to time during the whole process; e) the adhesion force via step time of the three structures; f) the interfacial stress distribution of DA and MIEA‐DA at the maximum adhesion moment; and g) the maximum normal stress of three structures with the pull‐off force.

Figure 4

The adaptability of adhesive structure to interface error. a) The force versus time curve during the loading–pulling process when there is an angular error (3°) between the target surface and adhesion structure; b) the change in contact length with time using CCD observations; c) the adaptability of both structures to different angle errors; d) the loading–pulling curves of the adhesive structures on a step surface (200 µm); e) the contact length of both structures on step surfaces with different heights; f) the adhesion strength to the stepped surfaces with different heights; and g–i) the adhesion strength to an array‐structured PMMA.

Figure 5

Influence of structural characteristics on adhesion performance. a) The effect of 2D discretization of the surface layer on adhesion strength; b) the adhesion strength on an uneven surface; c) the influence of adhesive layer thickness on adhesion performance; d,e) the tensile and compressive elastic moduli of porous structures with different porosities; and f) the adhesion strength of structures with different porosities to uneven surfaces.

Figure 6

The adaptability of MIEA‐DA to mutant surfaces. a) The schematic diagram of particle size; b) the normal adhesion strength of both structures to different particles; c) the ratio of decline in adhesion strength with increasing particle diameter; and d) the grasping process of MIEA‐DA on the PMMA plate with particles.

Figure 7

Verification of stable adhesion of multi‐stage discretized adhesion structure under different frequency vibrations. a) A schematic diagram of the anti‐vibrating characteristics of the adhesive structure during the process of surface adhesion; b) the schematic diagram of the test system and target objects; c–e) the anti‐vibration effect of ODA; and f–h) the anti‐vibration effect of MIEA‐DA.