Polypyrrole‐coated fiber‐scaffolds: Concurrent linear actuation and sensing

Abstract

Conducting polymers such as polypyrrole (PPy) can be deposited on various substrates to obtain conductive electroactive coatings. While electrochemical coatings are generally considered to be more effective, chemical coatings are more industrially suitable, especially on complex substrates. In this work, we aimed to explore the electro‐chemo‐mechanical response of conductive fiber scaffolds (CFS) prepared by coating PPy (chemically) on glucose‐gelatin nanofibre scaffolds. Electroactivity was readily observed in both aqueous and propylene carbonate solutions of lithium bis(trifluoromethanesulfonyl)imide, with mainly anion activity in both cases. A higher actuation response was achieved in the aqueous solutions with strain in the range of 1.2% and stress in the range of 3 kPa. Under both cyclic voltammetry and square wave potential steps driving, stable actuation for over 100 cycles was maintained. In addition to actuation, the CFS samples exhibited concurrent sensory properties, in sensing current densities and mechanical load. The PPy‐coated CFS material functioning as both an actuator and a sensor is envisaged to have potential applications in smart materials, soft robotics or e‐skin. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48533.

Concept of an artificial muscle design on polypyrrole nanofiber scaffolds

“…Fig 1A shows that the CFS-PPy/DBS samples grew during 11.1h under a constant electropolymerization potential of 2.55 V, while the electropolymerization of the CFS-PPy/TF sample was a more resistive process, going through a potential maximum of 3.45 V after 0.5h and then decreasing gradually to 3.22 V by the end of the polymerization time. These observations can be attributed to the different electronic conductivity of the samples immersed in different electrolytes; 0.42 ± 0.2 S cm -1 in aqueous-ethylene glycol solution, and 0.11 ± 0.1 S cm -1 in PC solution similar to those found in a previous work [29]. The reference electropolymerization of PPy/DBS and PPy/TF films on stainless steel sheets (S1 Fig) required lower voltages: 1.17 V for PPy/TF and 0.9 V for PPy/DBS, due to the higher conductivity of the underlayer, but also pointing to less overoxidation-degradation processes during the material generation.…”

“…Following those ideas for increasing the mechanical performance of linear actuators our goal here was to use conductive nanofiber scaffold material coated with electropolymerized PPy for designing biomimetic active materials, which could be comparable to natural skeletal muscles in terms of structure, achievable strain and stress, and importantly-with long life time. The conductive nanofiber scaffold (CFS) consist of chemical coated used in previous works [28,29] as the substrate for electrodes to develop new materials by electropolymerization. This material can be stretched up to 17% without a major loss of conductivity.…”

Multifunctionality of Polypyrrole Polyethyleneoxide Composites: Concurrent Sensing, Actuation and Energy Storage

“…Intense studies have been carried out in the past [ 9 , 11 , 28 ] to verify concurrent actuation and sensing properties of chemically [ 10 ] and electrochemically [ 29 ] polymerized PPy films. The evolution of the energy devoured by the reaction driving the actuator adapts to (senses) the energetic conditions (electrical, thermal, mechanical or chemical).…”

“…The energy of the reacting molecular motors adapts instantaneously to (senses) the ambient mechanical, chemical or thermal conditions. Various studies [ 7 ] of conducting polymers demonstrating concurrent actuation and sensing functions have been reported revealing that the motors can sense the electrolyte concentration [ 8 ], the working temperature [ 9 ], the mechanical loads on the actuator [ 10 ] and solvent of the electrolyte solution [ 11 ].…”

Conductive Electrospun Nanofiber Mats

“…Harjo et al developed conductive fiber scaffolds by coating electrospun glucose-gelatin nanofiber mats with polypyrrole and investigated their electro-chemo-mechanical response, showing stable actuation for more than 100 cycles as well as reasonable sensor properties [100]. They found conductivities of approximately 3 µS/cm in the unstretched state and approximately half this value when stretched in aqueous or organic electrolyte solutions.…”