With the rise of ion-based devices using soft ionic conductors, ionotronics show the importance of matching electronic and biological interfaces. Since textiles are conformal, an essential property for matching interfaces, light-weight and comfortable, they present as an ideal candidate for a new generation of ionotronics, i-textiles. As fibers are the building blocks of textiles, ionically conductive fibers, named ionofibers, are needed. However, ionofibers are not yet demonstrated to fulfill the fabric manufacturing requirements such as mechanical robustness and upscaled production. Considering that ionogels are known to be conformal films with high ionic conductivity, ionofibers are produced from commercial core yarns with specifically designed ionogel precursor solution via a continuous dip-coating process. These ionofibers are to be regarded as composites, which keep the morphology and improve the mechanical properties from the core yarns while adding the (ionic) conductive function. They keep their conductivity also after their integration into conformal fabrics; thus, an upscaled production is a likely outlook. The findings offer promising perspectives for i-textiles with enhanced textile properties and in-air electrochemical applications.

Conjugated polymers such as polypyrrole can be electrochemically oxidised and reduced. These redox reactions are accompanied by a flow of counter ions and solvent from the electrolyte into or out of the polymer matrix in order to maintain charge balance and osmotic pressure, resulting in an electrochemically induced volume change of the conjugated polymer. This volume change can be exploited to fabricate electrochemically driven actuators in various formats from bending bilayer microactuators to macroscopic textile actuators. Yarn and textile actuators are fabricated by coating commercially yarns and fabrics with the conjugated polymers. First a thin layer of PEDOT (poly(3,4-ethylenedioxythiophene)) is applied to make the yarns or fabrics electrically conductive. Thereafter the yarns/fabrics are coated with electromechanically active polypyrrole using electrochemical synthesis. Next the yarn or textile actuators can be actuated by applying the appropriate redox potentials. In order to achieve in-air actuation, the yarns or fabrics will be coated with novel ionogels (gelled semi-solid electrolytes), that function as the ion source/sink to drive the electrochemical reactions. Two of such ionogel coated yarns will be assembled forming the anode/cathode pair of the electrochemical circuit. Using advanced textile manufacturing such yarn actuators can be integrated into fabrics using knitting or weaving. The latest results of our textile actuators both operating in liquid electrolytes as in-air will be presented. Fig. 1 A textile actuator with 4 inlay-knitted, in-air operating yarn actuators. Figure 1

Conjugated polymers (CPs), as exemplified by polypyrrole, are intrinsically conducting polymers with potential for development as soft actuators or artificial muscles for numerous applications. Significant progress has been made in the understanding of these materials and the actuation mechanisms, aided by the development of physical and electrochemical models. Current research is focused on developing applications utilizing the advantages that CP actuators have (e.g., low driving potential and easy to miniaturize) over other actuating materials and on developing ways of overcoming their inherent limitations. CP actuators are available as films, filaments/yarns, and textiles, operating in liquids as well as in air, ready for use by engineers. Here, the milestones made in understanding these unique materials and their development as actuators are highlighted. The primary focus is on the recent progress, developments, applications, and future opportunities for improvement and exploitation of these materials, which possess a wealth of multifunctional properties.

This chapter outlines the various methods that have been developed in the past three decades to characterize the electroactive performance of conducting polymers (CP) to provide fundamental metrics such as strain, strain rate, stress, force, modulus of elasticity, and work capacity. In addition to providing metrics, these characterization techniques have served as valuable tools for studying CPs, providing a greater understanding of the actuation process, optimizing synthesis conditions, and geometric parameters for optimal device performance. The issues associated with the determination of metrics and the need for standardization are discussed.

Conducting polymers such as polypyrrole are biocompatible materials used in bioelectronic applications and microactuators for mechanobiology and soft microrobotics. The materials are commonly electrochemically synthesised from an electrolyte solution comprising pyrrole monomers and a salt, which is incorporated as the counter ion. This electrosynthesis results in polypyrrole forming a three-dimensional network with extensive cross-linking in both the alpha and beta positions, which impacts the electro-mechanical performance. In this study we adopt a 'blocking strategy' to restrict and control cross-linking and chain branching through beta substitution of the monomer to investigate the effect of crosslinking on the electroactive properties. Methyl groups where used as blocking groups to minimise the impact on the pyrrole ring system. Pyrrole, 3- and 3,4-methyl substituted pyrrole monomers were electro-polymerised both as homo-polymers and as a series of co-polymer films. The electroactive performance of the films was characterised by measuring their electrochemical responses and their reversible and non-reversible film thickness changes. This showed that altering the degree of crosslinking through this blocking strategy had a large impact on the reversible and irreversible volume change. These results elaborate the importance of the polymer structure in the actuator performance, an aspect that has hitherto received little attention.

Micro-actuators have been developed that exploit the electrochemically induced volume change of the electro-active polymer polypyrrole. The strain regime is inherently complex at a physical level and whilst volume change can be estimated indirectly using, for instance, bending beam theory, such methods become unreliable for large deflections owing to limitations in the mathematical model. A new non-contact measuring technique based on laser micrometry is presented to characterize the time-dependent expansion of electro-active films such as polypyrrole. Measurements have been made which demonstrate that the observed strain is dependent on film thickness. The new measurement technique is straightforward to perform and it is anticipated that it can be used for future materials development and performance assessment, including long-term stability evaluations and operational failure studies of the films.

A synthetic chemical strategy aimed at altering the cross-linking density of the electropolymerized conjugated polymer polypyrrole has been devised and implemented. The actuation performance of the synthesized material was assessed using a new type of apparatus capable of making rapid, non-contact dynamic measurements. The affect of cross-linking on the actuation performance of polypyrroles, was investigated.

Polypyrrole is electromechanically active and actuates due to ion and solvent movements during redox switching, causing both reversible and irreversible swelling. The swelling of polymers is known ...