Reverse Adhesion of a Gecko-Inspired Synthetic Adhesive Switched by an Ion-Exchange Polymer–Metal Composite Actuator

Abstract

Inspired by how geckos abduct, rotate, and adduct their setal foot toes to adhere to different surfaces, we have developed an artificial muscle material called ion-exchange polymer–metal composite (IPMC), which, as a synthetic adhesive, is capable of changing its adhesion properties. The synthetic adhesive was cast from a Si template through a sticky colloid precursor of poly(methylvinylsiloxane) (PMVS). The PMVS array of setal micropillars had a high density of pillars (3.8 × 103 pillars/mm2) with a mean diameter of 3 µm and a pore thickness of 10 µm. A graphene oxide monolayer containing Ag globular nanoparticles (GO/Ag NPs) with diameters of 5–30 nm was fabricated and doped in an ion-exchanging Nafion membrane to improve its carrier transfer, water-saving, and ion-exchange capabilities, which thus enhanced the electromechanical response of IPMC. After being attached to PMVS micropillars, IPMC was actuated by square wave inputs at 1.0, 1.5, or 2.0 V to bend back and forth, driving the micropillars to actively grip or release the surface. To determine the adhesion of the micropillars, the normal adsorption and desorption forces were measured as the IPMC drives the setal micropillars to grip and release, respectively. Adhesion results demonstrated that the normal adsorption forces were 5.54-, 14.20-, and 23.13-fold higher than the normal desorption forces under 1.0, 1.5, or 2.0 V, respectively. In addition, shear adhesion or friction increased by 98, 219, and 245%, respectively. Our new technique provides advanced design strategies for reversible gecko-inspired synthetic adhesives, which might be used for spiderman-like wall-climbing devices with unprecedented performance.

Switchable Adhesives for Multifunctional Interfaces

“…[118,[121][122][123][124][125] The effect can also be achieved by shearing a micropillar array. This includes the loading paths (trajectory) as well as the time scales involved in contact formation.…”

“…One wall is then moved parallel to the other until failure occurs. 20 [132] 50 [182] 21 [112] 51 [56] 22 [125] 52 [60] 23 [128] 53 [66] 24 [131] 54 [184] 25 [144] 55 [198] 26 [101] 56 [74] 27 [80] 57 [87] 28 [142] 58 [67] 29 [143] 59 [86] 30 [136] 60 [98] [230] Of course, variations from our assumptions require more complex analysis.…”

One-dimensional polymer nanofiber arrays with high aspect ratio obtained by thermal nanoimprint method

“…In the early 2000s, a new concept inspired by natural phenomena was introduced. Many scientists started to explore the use of dry adhesives that inspired by gecko toe pads [16][17][18][19][20][21][22]. Such dry adhesives are non-toxic because they avoid harsh chemicals.…”

Programmable 3D Shape Changes in Liquid Crystal Polymer Networks of Uniaxial Orientation

“…Inspired by the desired multiple functionalities in the natural systems, researchers and scientists have put an increasingly large amount of research activities to develop novel biomimetic functional systems. For this regard, a variety of soft stimuli‐responsive materials, such as hydrogels, shape‐memory polymers (SMPs), and different types of electroactive polymers like ionic‐polymer–metal composites and dielectric elastomer actuators have been explored in order to recapitulate both structural and adaptive traits of the living organisms. Among all these active materials, liquid crystal polymer networks (LCNs) have been considered as the most appealing type of materials due to several significant features.…”