Free-Standing Faradaic Motors Based on Biocompatible Nanoperforated Poly(lactic Acid) Layers and Electropolymerized Poly(3,4-ethylenedioxythiophene)

Abstract

The electro-chemo-mechanical response of robust and flexible free-standing films made of three nanoperforated poly(lactic acid) (pPLA) layers separated by two anodically polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) layers, has been demonstrated. The mechanical and electrochemical properties of these films, which are provided by pPLA and PEDOT, respectively, have been studied by nanoindentation, cyclic voltammetry and galvanostatic charge-discharge assays. The unprecedented combination of properties obtained for this system is appropriated for its utilization as a Faradaic motor, also named artificial muscle. Application of square potential waves has shown important bending movements in the films, which can be repeated for more than 500 cycles without damaging its mechanical integrity. Furthermore, the actuator is able to push a huge amount of mass, as it has been proved by increasing the mass of the passive pPLA up to 328% while keeping unaltered the mass of electroactive PEDOT.

Free-Standing, Flexible Nanofeatured Polymeric Films Prepared by Spin-Coating and Anodic Polymerization as Electrodes for Supercapacitors

“…The procedure used for the preparation of multilayered films formed by alternated layers of PLA and PEDOT was reported in previous work [ 43 ] and is schematically summarized in Figure 1 . In brief, after spin-coating a sacrificial electroactive layer of PEDOT doped with polystyrene sulfonate (PEDOT:PSS) on a steel sheet (AISI 304) of 0.50 × 0.25 cm 2 , the rest of the process consisted in the sequential combination of three different steps.…”

“…After this, the second step involved the elimination of the nanospherical PVA domains by water-etching (steps “2” in Figure 1 ). It is worth noting that the diameter of such PVA nanofeatures, which were induced by the phase segregation between immiscible PLA and PVA during the spin-coating process, was adjusted to the thickness of the layer by selecting appropriated operational parameters (i.e., spinning speed, spinning time, and both concentration and solvent for the polymer solutions) [ 43 , 44 ]. Consequently, the electroactive material under the PLA layer became accessible through the nanoperforations obtained by removing PVA.…”

“…Moreover, the templating effect of the internal PEDOT layer on the external PLA layer is also reflected in the highest magnification micrograph ( Figure 3 b, right). Detailed description of the morphology and topography of 3PLA/2PLA films was provided in previous work [ 43 , 44 ] in which the effect of each layer was analyzed one-by-one.…”

“…Multilayered films were prepared by combining the spin-coating and the anodic polymerization techniques, following a recently reported procedure [ 43 ]. In brief, a steel sheet (AISI 304) of 0.50 × 0.25 cm 2 was coated with a sacrificial layer of PEDOT:PSS by spin-coating deposition (1200 rpm for 60 s).…”

“…It should be remarked that the amount of electrochemically active CP is the same for the two electrodes, hereafter denoted 3PLA/2PEDOT and 2PLA/2PEDOT, respectively. Therefore, differences between them have been attributed to the effect of the external PLA layer that, although it was found to be beneficious for electromechanical (i.e., faradaic motors) [ 43 ] and tissue engineering applications [ 44 ], has a detrimental effect for energy storage applications.…”