Stimuli-Responsive Polymer Nanocomposites Inspired by the Sea Cucumber Dermis

TLDR

Sea cucumbers can rapidly and reversibly alter dermis stiffness, a property thought to arise from regulated interactions among collagen fibrils within a low‑modulus matrix. The study aims to develop polymer nanocomposites that emulate the sea cucumber dermis architecture and achieve chemoresponsive mechanical adaptability. The authors fabricated composites of a rubbery host polymer and rigid cellulose nanofibers that mimic the dermal structure and enable chemoresponsive mechanical changes. The composites exhibit reversible modulus reductions from 800 to 20 MPa (a 40‑fold decrease) with a chemical regulator, and when a thermally responsive host polymer is used, modulus changes from 4200 to 1.6 MPa under physiological conditions.

Abstract

Sea cucumbers, like other echinoderms, have the ability to rapidly and reversibly alter the stiffness of their inner dermis. It has been proposed that the modulus of this tissue is controlled by regulating the interactions among collagen fibrils, which reinforce a low-modulus matrix. We report on a family of polymer nanocomposites, which mimic this architecture and display similar chemoresponsive mechanic adaptability. Materials based on a rubbery host polymer and rigid cellulose nanofibers exhibit a reversible reduction by a factor of 40 of the tensile modulus, for example, from 800 to 20 megapascals (MPa), upon exposure to a chemical regulator that mediates nanofiber interactions. Using a host polymer with a thermal transition in the regime of interest, we demonstrated even larger modulus changes (4200 to 1.6 MPa) upon exposure to emulated physiological conditions.