Rapidly responsive smart adhesive-coated micropillars utilizing catechol-boronate complexation chemistry

Smart adhesive hydrogels containing 10 mol% each of dopamine methacrylamide (DMA) and 3-acrylamido phenylboronic acid (APBA) were polymerized in situ onto polydimethylsiloxane (PMDS) micropillars with different aspect ratios (AR = 0.4, 1 and 2). Using Johnson-Kendall-Roberts (JKR) contact mechanics tests, the adhesive-coated pillars demonstrated strong wet adhesion at pH 3 (W-adh = 420 mJ m(-2)) and can be repeatedly deactivated and reactivated by changing the pH value (pH 9 and 3, respectively). When compared to the bulk adhesive hydrogel of the same composition, the adhesive-coated pillars exhibited a significantly faster rate of transition (1 min) between strong and weak adhesion. This was attributed to an increased surface area to volume ratio of the adhesive hydrogel-coated pillars, which permitted rapid diffusion of ions into the adhesive matrix to form or break the catechol-boronate complex.