Mahiar Hamedi1
KTH1
Intelligent systems combine sensing, actuation, and computation to achieve complex tasks and functions. Soft electrically controlled multifunctional materials, especially hydrogels, are the most promising materials for such systems as they are as adaptable as biological systems yet compatible with advanced systems through electronics.<br/>We describe an electroactive hydrogel fabricated from cellulose nanofibrils from trees, and conductive nanomaterials, like CNTs or 2D MXenes. These nanoparticles self-assemble into an anisotropic composite networks with an open mesoporous structure that can hold lots of water and be highly permeable to substances in their surroundings. The anisotropy of the network allows high expansion in one direction while maintaining very high strength and high electric conductivity in the other.<br/>The electrochemical charge/discharge of the conductors in the hydrogels controls the internal salt concentration and consequently their osmotic swelling. This allows direct electrically controlled actuation where around 700 water molecules expand/contract the structure for each ion/electron pair inserted/de-inserted at only ±1 volt, resulting in up to 300% electroosmotic expansion, with very high pressures reaching 1 MPa.<br/><br/>This mode of electronic actuation has not been shown before. We call these electroosmotic (ECO) actuators. Our ECO hydrogel actuators have emergent properties not present in any previously known soft material. ECOs allow formonolithic integration of sensors and many other functions into the same composite, rendering a new form of smart soft material not achieveable with other materials systems.<br/><br/>Reference:<br/><i>”Electrochemically Controlled Hydrogels with Electrotunable Permeability and Uniaxial Actuation</i><i>”, </i>T Benselfelt, J Shakya, P Rothemund, S B Lindström, A Piper, T E Winkler, A Hajian, L Wågberg, C Keplinger, M M Hamedi, <b>Advanced Materials </b>2023