Electromechanically active polymer actuators based on biofriendly choline ionic liquids

Abstract

Smart and soft electroactive polymer actuators have many beneficial properties, making them attractive for biomimetic and biomedical applications. However, the selection of components to fabricate biofriendly composites has been limited. Although biofriendly options for electrodes and membranes are available, the conventional ionic liquids (ILs) often used as the electrolytes in the actuators have been considered toxic in varying degrees. Here we present a smart electroactive composite with carefully designed and selected components that have shown low toxicity and a biofriendly nature. In the present study, polypyrrole-PVdF trilayer actuators using six different choline ILs were prepared and characterized. Choline ILs have shown promise in applications where low environmental and biological impact is critical. Despite this, the anions in ILs have a strong impact on toxicity. To evaluate how the anions effect the bioactivity of the ILs used to prepare the actuators, the ILs were tested on different microbial cultures (Escherichia coli, Staphylococcus aureus, Shewanella oneidensis MR-1) and HeLa cells. All of the selected choline ILs showed minimal toxic effects even at high concentrations. Electro-chemo-mechanical characterization of the actuators indicated that polypyrrole-PVdF actuators with choline ILs are viable candidates for soft robotic applications. From the tested ILs, choline acetate showed the highest strain difference and outperformed the reference system containing an imidazolium-based IL.

Understanding the Behavior of Fully Non-Toxic Polypyrrole-Gelatin and Polypyrrole-PVdF Soft Actuators with Choline Ionic Liquids

“…PPy-gelatin actuators were made using the electrochemical deposition of PPy on gelatin membranes and afterwards immersing the laminates in choline IL (Table 1). The synthesis process of the three choline ILs used in this research as well as the three additional ones, to put the results in a wider context, and their corresponding properties have been reported previously [15].…”

“…PPy-gelatin actuators were made using the electrochemical deposition of PPy on gelatin membranes and afterwards immersing the laminates in choline IL (Table 1). The synthesis process of the three choline ILs used in this research as well as the three additional ones, to put the results in a wider context, and their corresponding properties have been reported previously [15]. The gelatin membranes were prepared by electrospinning from acetic acid solution and crosslinking with glucose, which helps to enhance the mechanical properties and achieve insolubility in an aqueous environment without compromising biocompatibility.…”

“…The ionic conductivities of the gelatin membranes immersed in ILs were determined using a method described previously [15]. The measurements of the ionic conductivities of the ILs were carried out using a Micrux microfluidic chip with interdigitated gold electrodes.…”

“…In our previous work, we have demonstrated that this obstacle can be overcome with the right choice of ILs. We have shown that choline carboxylates are harmless towards Escherichia coli, Staphylococcus aureus, Shewanella oneidensis MR-1, and a HeLa cell-line, even at high concentrations, and can be used in IEAP actuators [15].…”

Investigation on the Role of Ionic Liquids in the Output Signal Produced by Bacterial Cellulose-Based Mechanoelectrical Transducers

“…According to results already available for BC–IL actuators, a structure consisting of BC, infused with 1-Ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF 4 ) as the IL, and covered with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT-PSS), as Conducting Polymer (CP) is investigated. More specifically, EMIM-BF 4 has been already proposed for the realization of actuators, being widely available in the market [ 32 ], though greener ILs [ 41 ], or even classes of solvents, such as Deep Eutectic Solvents (DES) could be investigated to this aim, as environmentally friendly solvents [ 42 , 43 , 44 , 45 ]. In the same way, electronic conductive layers other than CPs, such as carbon-based layers [ 46 ] could be used for the electrodes.…”