Honey-inspired thermally hysteretic adhesives for high strength and reversible underwater adhesion

Abstract

Inspired by the thermal hysteresis of honey, we report an atypical temperature‑responsive strategy to overcome the strength-switchability trade-off in underwater adhesives. By programming the reversible polymerization-crystallization of the natural small-molecule thioctic acid (TA) using a long-chain alkylated TA derivative as “molecular pollen” and tris(2-carboxyethyl)phosphine (TCEP) as a stabilizer, we designed a robust yet highly reversible underwater adhesive. Upon mild heating, TA polymerizes into a metastable polyTA complex stabilized by TCEP and plasticized by the molecular pollen, maintaining a supercooled fluid state even below its crystallization temperature to enable thorough underwater wetting. Cooling underwater triggers depolymerization, releasing TA monomers that co‑crystallize with the molecular pollen to induce complete solidification with high cohesion. This mild thermal cycling enables wide-range cohesion modulation, yielding robust underwater adhesion (2.21 MPa on steel within 24 h) and high switching efficiency (>99.9 %) within a narrow temperature window (ΔT ≤ 30 °C). With honey-like thermal hysteresis near body temperature, the adhesive provides secure wound sealing and stable catheter fixation (≥7 d) in vivo, followed by minimal-trauma removal with reduced inflammation under gentle thermal stimulation. This sustainable biomimetic strategy resolves the “switchability conflict” in underwater adhesives, with promising applicability in medical device fixation, wearable electronics, and reversible assembly.