Hybrid nanocomposites based on electroactive hydrogels and cellulose nanocrystals for high-sensitivity electro–mechanical underwater actuation

Abstract

We report the synthesis, fabrication and characterization of a hybrid hydrogel/cellulose
\nnanocomposite, which exhibits high-performance electro–mechanical underwater actuation and
\nhigh sensitivity in response to electrical stimuli below the standard potential of water
\nelectrolysis. The macromolecular structure of the material is constituted by an electroactive
\nhydrogel, obtained through a photo-polymerization reaction with the use of three vinylic comonomers:
\nNa-4-vinylbenzenesulfonate, 2-hydroxyethylmethacrylate, and acrylonitrile.
\nDifferent amounts (from 0.1% to 1.4% w/w) of biodegradable cellulose nanocrystals (CNCs)
\nwith sulfonate surface groups, obtained through the acidic hydrolysis of sulphite pulp lapsheets,
\nare physically incorporated into the gel matrix during the synthesis step. Freestanding thin films
\nof the nanocomposites are molded, and their swelling, mechanical and responsive properties are
\nfully characterized. We observed that the embedding of the CNCs enhanced both the material
\nYoung’s modulus and its sensitivity to the applied electric field in the sub-volt regime (down to
\n5mV cm−1). A demonstrator integrating multiple actuators that cooperatively bend together,
\nmimicking the motion of an electro-valve, is also prototyped and tested. The presented
\nnanocomposite is suitable for the development of soft smart components for bio-robotic
\napplications and cells-based and bio-hybrid fluidic devices fabrication.