Biomimetic Polymer Adhesives

Abstract

Nature is filled with various living organisms, ranging from micron scale fungi to large scale vertebrates, which possess unique adhesion characteristics, including self-cleaning, antifouling, and reusability in both wet and dry environments. Inspired from the natural adhesives, humans have endeavored to mimic and acquire those adhesion characteristics in artificially designed adhesives. Over several decades, researchers have employed various fabrication techniques and have used a variety of materials, predominantly polymers, to manufacture artificial adhesives which emulate the fundamental design aspects of the bioadhesion to match their adhesion performance. In this review, we briefly discuss the fundamentals aspects of adhesion, biomimetic design principles (derived from geckos, mussels, octopuses, and tree frogs), state of the art adhesion performance of the fabricated adhesives, their applications, and future outlook for the polymer-based adhesives both under dry and wet conditions.

Increasing the Scale and Decreasing the Cost of Making a Catechol-Containing Adhesive Polymer

“…The organic phase was dried over anhydrous MgSO 4 , and the solvent evaporated under vacuum to yield a colorless oil (30.4 g, 100%). 1 H NMR (CDCl 3 , 300 MHz): δ (ppm) 6.95−6.80 (m, 3H, H Ar ), 4.86 (q, J = 6.5 Hz, 1H, −CH(OH)−CH 3 ), 3.91−3.85 (m, 6H, −OCH 3 ), 1.75 (bs, 1H, −OH), 1.48 (d, J = 6.5 Hz, 3H, −CH(OH)−CH 3 ). 13 13 C NMR spectra were collected using a Varian Inova 300 MHz spectrometer employing deuterated chloroform (CDCl 3 ) for solvent.…”

“…Biomimetic principles have become prominent in the design of new adhesive materials. 1 The micro-and nanometer-scale features of gecko toe pads have given rise to several structured materials that can bond well and even detach on demand. Such systems are particularly well suited to dry, smooth surfaces.…”

“…The product was extracted three times with diethyl ether (1 × 400 mL, 2 × 300 mL). The organic phase was washed with brine three times (1 × 300 mL, 2 × 200 mL) and dried over anhydrous MgSO 4 , and the solvent was evaporated under vacuum to yield a light yellow oil (24.1 g, 88.0%) 1. H NMR (CDCl 3 , 300 MHz): δ (ppm) 6.95−6.76 (m, 3H, H Ar ), 6.63 (dd, J = 10.9, 17.6 Hz, 1H, Ph-CH� CH 2 ), 5.59 (d, J = 17.6 Hz, 1H, Ph-CH�CH 2 ), 5.12 (d, J = 10.8, 1H, Ph-CH�CH 2 ), 3.90−3.82 (m, 6H, −OCH 3 ) 13.…”

“…Reagents Used for the Methyl Group DeprotectionMethodolgy applied for the polymer deprotection was directly adapted from the references cited. b Me−O cleavage was calculated by1 H NMR spectroscopy at the end of the reaction. c Polymer decomposition.…”

Tribological Behavior of Bioinspired Surfaces

“…Meanwhile, some spiders and lizards can provide dry adhesion and move on vertical surfaces (rough) due to the presence of compliant layers present on the surface of their attachment pads [ 225 ]. Flies, grasshoppers, bugs, and tree frogs have less compliant layers on the surface of attachment pads, and the adhesion occurs on rough surfaces because the animals inject a wetting liquid into the pad–substrate contact area, generating a relatively long-range attractive interaction provided by the formation of capillary bridges [ 226 ]. On the other hand, the surface layer on the cheetah paws has more compliant layers, providing strong traction to the rough surface [ 227 ].…”