Effect of fibril shape on adhesive properties

Abstract

Research into the gecko’s adhesive system revealed a unique architecture for adhesives using tiny hairs. By using a stiff material (β-keratin) to create a highly structured adhesive, the gecko’s system demonstrates properties not seen in traditional pressure-sensitive adhesives which use a soft, unstructured planar layer. In contrast to pressure sensitive adhesives, the gecko adhesive displays frictional adhesion, in which increased shear force allows it to withstand higher normal loads. Synthetic fibrillar adhesives have been fabricated but not all demonstrate this frictional adhesion property. Here we report the dual-axis force testing of single silicone rubber pillars from synthetic adhesive arrays. We find that the shape of the adhesive pillar dictates whether frictional adhesion or pressure-sensitive behavior is observed. This work suggests that both types of behavior can be achieved with structures much larger than gecko terminal structures. It also indicates that subtle differences in the shape of these pillars can significantly influence their properties.

Elastic Energy Storage Enables Rapid and Programmable Actuation in Soft Machines

“…Upon pressurization, the expansion of the prestressed elastomer opens the gripper (Figure D). The surface of PSAs can be microtexturized during the molding process (Figure C,D; Figure S1, Supporting Information), enhancing their friction against the surfaces they are perching on (Figures S2 and S3, Supporting Information). These PSAs can hang upside down from rod‐like objects (Figure E top), thin vertical bars (Figure E bottom), and 116° overhangs (Figure F; Movie S1, Supporting Information) due to their elastic restoring forces and the high coefficient of friction (up to ≈3; see Text S1 in the Supporting Information) provided by the texturized surface.…”

Vorstandssitzung

“…Previous work has shown the importance of the tip geometry on the adhesion and friction of microfiber adhesives 8, 37–40. To investigate the importance of tip geometry in our proposed micropillars, we used two distinct pillar types that were similar in all geometric and material parameters except for the shape of the tip.…”

Bionica e Design

“…Alcuni ricercatori dell'Università di Stanford (Parness et al, 2009;Santos et al, 2008;Soto et al, 2010) hanno creato un robot (S ckybot) ispirato al geco (Fig. 3 e, f): il proto po messo a punto dagli scienzia , benché in grado di camminare su superfici ver cali lisce (plas ca, vetro, maiolica) e recentemente perfezionato (Zou et al, 2013), è ancora molto lontano dall'efficienza del modello biologico.…”