Bioinspired artificial muscle-sensor dual devices based on conducting polymers functionalized electrospun fiber networks


Project Director: Dr. Mihaela BEREGOI

Development of new materials for fabricating low cost, accessible bioinspired soft robots represents a great challenge because of the difficulty for closely mimicking the models from nature. A generic term utilized very often in soft robotics domain is “artificial muscle” which describes any device that can transform various kind of energy into mechanical motion. Engineering efficient materials utilized for manufacturing artificial muscles with similar properties than biological muscles should take into account a lot of experimental parameters such as material type, its morphology, geometry, etc. The materials used for designing artificial muscles can be divided in three major classes: electroactive polymers, shape memory alloys and electroactive ceramics. The use of first class in such applications presents manifold advantages such as low working voltages, versatility in preparation, fast response time, etc. In this context, the present project aims to develop a reproducible method for fabricating artificial muscles with sensing capabilities by using conducting polymers as electroactive materials and fibers as substrates. Thus, electrospinning will be employed for preparing fiber networks with optimum morphology, sizes and densities. In order to make them conductive, a thin metal layer will be deposited on the fiber networks for a better control of the movement. Further, the metalized fibers will be functionalized with a suitable conducting polymer in order to obtain active materials with improved features. The conducting polymer coated networks will be analyzed from morphological, electrochemical, structural, mechanical and actuation point of view. The experimental parameters will be correlated with the artificial muscle actuation performances for finding the best material configuration and establishing the actuation mechanism. Likewise, the capacity of the fabricated device to identify modification of external stimuli or some biomolecules interactions will be investigate.

This work was supported by a grant of the Romanian Ministry of Education and Research, CCDI – UEFISCDI project number PN-III-P1-1.1-PD-2019-1066, within PNCDI III.

Objectives

Implementation of this project involves two main objectives: the preparation of the precursor materials (conducting polymer coated electrospun fiber meshes) with the most suitable features and the characterization of the obtained structures from actuating and sensing point of view.

As well, a series of specific secondary objectives (which represent the main project activities) will be considered to reach the project goal as follows:

A1. Optimization of the electrospun fiber meshes preparation and metallization process;

A2. Electrochemically coverage of the metalized micro/nano-structures with the chosen conducting polymer and analyzing the artificial muscles actuation performances as function of fabrication parameters;

A3. Designing, fabrication and characterization of an original  device which will operate as dual device with actuation and sensing capabilities.

Dr. Mihaela Beregoi - as project leader

Prof. Dr. Eng. Sorin Ion Jinga - as mentor

The project scope was to develop a dual device which simultaneously works as artificial muscle (produces a movement when an external stimulus is applied) and sensor (identifies some external parameters modifications) by using electrospun fibers and conducting polymers. The preparation procedure involved three main steps: the first step was the optimization and preparation of freestanding micro/nanofiber meshes utilizing the electrospinning technique. Thus, many polymers were tested and it was found that the nylon 6/6 nanofibers and microribbons (which were obtained changing the polymer precursor concentration and electrospinning parameters) are the best options from actuation point of view. The second step was consisted in metallization in different configuration of the freestanding nanofibers and microribbons by using sputtering deposition in order to have a better control of the movement. Pt, Ag and Au metals were tested, deposited in four ways and the metallized meshes were optical and electrical characterized. It was found that sheet resistance/conductivity of each configuration depends on the predominant metal, nanofiber meshes with more Au have the best sheet resistance/conductivity, followed by Ag and Pt. In the last step, conducting polymers such as polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) were electrochemical synthesized on microribbon meshes metalized with Au, Pt and Ag segments and respective on nanofiber nets covered with a continuous Au film. The prepared structures were electrical, electrochemical, structural and morphological characterized, and PEDOT:PSS covered nanofibers were analyzed from cytotoxicity point of view using osteoblast and fibroblast cells. Also, their actuation properties were highlighted as function of metallization configuration and deposited conducting polymer. The best actuation performances were identified in the case of microribbons covered with a continuous Au layer and PPy and further such materials were tested as sensors. It was demonstrated that they can work as mechanical or chemical sensors by identifying the mass weight modification attached the artificial muscle and respective the changes of the electrolyte concentration. These results will be useful for designing updated devices utilizing structures with morphologies and functionalities that closely mimic the biological models. The project objectives were completely fulfilled, the results were published in international ISI journals and presented to conferences.

"Conductive Polymeric Fibers for Artificial Muscle Applications" - master thesis

  1. N. Preda, A. Costas, M. Beregoi, N. Apostol, A. Kuncser, C. Curutiu, F. Iordache, I. Enculescu. Functionalization of eggshell membranes with CuO–ZnO based p–n junctions for visible light induced antibacterial activity against Escherichia coli, Sci. Rep. 10 (2020) 20960.
  2. M.-C. Bunea, M. Beregoi, A. Evanghelidis, A. Galatanu, I. Enculescu. Direct and remote induced actuation in artificial muscles based on electrospun fiber networks, Sci. Rep. 12 (2022) 13084.
  3. M. Beregoi, S. Beaumont, S.I. Jinga, T.F. Otero, I. Enculescu. Chemical sensing and actuation properties of polypyrrole coated fibers, Smart Mater. Struct. 31 (2022) 105012.
  4. Beregoi, S. Beaumont, A. Evanghelidis, T.F. Otero, I. Enculescu. Bioinspired polypyrrole based fibrillary artificial muscle with actuation and intrinsic sensing capabilities, Sci. Rep.  12 (2022) 15019.

Conference attendances:

  1. Nanofibers, Applications and Related Technologies - NART 2021, Istanbul, Turkey (on-line), 08-10 September 2021 - oral presentation;
  2. 6th Ed. Smart Materials and Surfaces – SMS 2021 Conference and Exhibition, Milan, Italy (on-line), 20-22 October 2021 - oral presentation;
  3. School and Conference of Romanian Electron Microscopy Society - C.R.E.M.S, Magurele, Romania (on-line), 18-22 October 2021;
  4. 13th International Conference on Nanotechnology: Fundamentals and Applications- ICNFA’22, Prague, Czech Republic (on-line), 03-05 August 2022 - oral presentation;
  5. 71st Lindau Nobel Laureate Meetings, Lindau, Germany (on-line), 26 June- 01 July 2022.

mihaela.oancea@infim.ro

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