Direct laser writing of electro-actuating microstructures Jason Delente , Srikanth Kolagatla, Donagh Mc Ginley, Colm Delaney, Larisa Florea* School of Chemistry & AMBER, The SFI Research Centre for Advanced Materials and BioEngineering Research, Trinity College Dublin, Dublin 2, Ireland. Stimuli-responsive hydrogels are highly attractive materials as they can be studied in aqueous environments, are easily functionalised to respond to specific stimuli and enable the diffusion of the solvent/analytes within their structures. Therefore, the material selected for the fabrication of actuator is of crucial importance depending on the desired stimuli (pH, temperature, analyte, potential, light, etc). Electro-active hydrogels, which are gels that convert the energy of an applied electric field to a mechanical motion, are usually composed of a monomer which can either be a pH-sensitive group that will be charged or neutral depending on the pH or can be a permanently charged moiety. Depending on the polymer used, it has been shown that the electro-actuation involves several mechanisms such as the Coulomb mechanism, the electroosmosis mechanism, the electrochemical mechanism and the dynamic enrichment/depletion mechanism which can operate simultaneously. 1 One of the major drawback for macroscale actuators is that they usually demonstrate slow actuation which limits their use. 2, 3 By using two- photon polymerisation (TPP), a direct laser writing technique which enables the fabrication of complex 3D polymer microstructures with a resolution of 100 nm, it is possible to accurately form electro-actuating microstructures which could actuate faster than their macroscale counterparts as well as require reduced electric field. Herein is presented the fabrication of electro-actuating microstructures by TPP, with an in-depth study of their properties along with the influence of several factors on the electro-actuation (variation of pH, concentration of electrolyte, position relative to the electrode and strength of the electric field). References 1. J. Glazer, M. van Erp, A. Embrechts, S. G. Lemay and E. Mendes, Soft Matter , 2012, 8 , 4421-4426. 2. D. Morales, E. Palleau, M. D. Dickey and O. D. Velev, Soft Matter , 2014, 10 , 1337-1348. 3. D. Han, C. Farino, C. Yang, T. Scott, D. Browe, W. Choi, J. W. Freeman and H. Lee, ACS Appl. Mater. Interfaces , 2018, 10 , 17512-17518.
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