Session: Rising Stars of Mechanical Engineering Celebration & Showcase

Paper Number: 147877

147877 - Robust, Reversible, and Stimuli-Responsive Thermodynamic Adhesion in Hydrogels 

Hydrogels are soft and hydrated materials similar to our body tissues. This similarity makes them useful for creating soft machines that better interact with human bodies. Applications of soft machines include medical implants, wearable devices, and biomimetic robots. Unlike conventional machines that are assembled by rigid parts like nuts and bolts, soft machines are assembled through deformable adhesion. Although some existing studies have realized hydrogel adhesion that can reliably survive larger deformation, it is difficult to reversibly switch the adhesion on and off so that the soft machine can be repaired or reconfigured by part exchange, which is a common practice in conventional machines. 

Here we propose to a novel mechanism to realize reversible, stimuli-responsive hydrogel adhesion, osmocapillary adhesion. Hydrogel contains water. Due to capillary action, water is wicked into the interfacial gap during contact. Due to osmosis, hydrogels absorb water on their surface, putting the interfacial water under tension, which in turn generates adhesion. Since the osmosis in a hydrogel is stimuli-responsive, the osmocapillary adhesion is stimuli-responsive. Since both the osmosis and wicking of the interfacial water are reversible, osmocapillary adhesion is reversible. Our preliminary results have shown that osmocapillary adhesion can readily realize 100kPa level adhesion strength 100J/m^2 level adhesion energy by tuning the bulk hysteresis and osmotic pressure.

Presenting Author: Qihan Liu University of Pittsburgh

Presenting Author Biography: Dr. Liu is an assistant professor at the University of Pittsburgh. His research engages in multiple aspects of the mechanics and manufacturing of soft materials, with particular focuses on stimuli-responsive adhesion between soft materials and fiber-reinforced soft composites.

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