Electro-Responsive, Smart Adhesive Utilizing Mussel Adhesive Chemistry

A smart adhesive is capable of switching between its adhesive and non-adhesive state in response to externally applied stimuli (e.g., pH, temperature, light). Smart adhesives with on-demand switching of adhesion have potential applications in the biomedical field (e.g., painlessly removable wound dressing, artificial prostheses attachment, and wearable sensors for health monitoring). Moreover, these adhesives are of great interest for on-demand attachment and detachment of electronic sensors and robotic locomotion. However, most of the existing smart adhesives are limited to dry adhesion and demonstrate poor performance in the presence of water. Marine mussels secrete adhesive proteins that enable these organism to anchor themselves to various substrate (i.e., ship hull, rock) in a rough, intertidal zone. These mussel foot proteins contain a unique amino acid, L-3, 4 dihydroxyphenylalanine (DOPA), that is responsible for strong interfacial binding and curing of the proteins. The catechol side chain of DOPA is capable of participating in various reversible interactions depending on its oxidation state. In this presentation, I will describe our efforts in controlling the oxidation state of catechol in designing electro-responsive smart adhesive that can bind to wet surfaces. A custom-built Johnson−Kendall−Roberts (JKR) contact mechanics test setup was used to evaluate the interfacial binding property of catechol-containing adhesive and to demonstrate the feasibility of using applied electricity to directly deactivate catechol-based adhesive that is bonded to a surface. Additionally, the effect of incorporating conductive pyrene monomer and phenylboronic acid as temporary protecting group on the deactivation and reversibility of the adhesive was evaluated. Specifically, addition of 26 mol% of 1-pyrenemethyl methacrylate enabled the deactivation of the adhesive using a voltage as low as 1 V. An electro-responsive adhesive can potentially be integrated with electronic devices, which will offer users unprecedented control over the interfacial binding properties of the adhesive. Additionally, an adhesive that demonstrates switchable adhesive property in response to a low applied voltage provides improved control over their operation and electrical safety.