Textile actuators based on coiled yarns coated with conductive polymers aregaining increasing attention for wearable applications. Coiled yarn actuators showsuperior performance due to the geometrical and mechanical effects of the coils.A typical configuration to use coiled yarn actuators in air consists of two coiledyarns coated with different conductive polymers, connected through an ionogel.One coiled yarn actuator is cation-driven, while the other is anion-driven, ensuringsynchronized actuation strains. Although coiled yarn actuators generally showhigh actuation performance in electrolytes, developing a high performance, andstable yarn actuator that works effectively in air remains a challenge for manyapplications. In this study, we employed a step-by-step approach to systematicallyidentify the limitations affecting actuation in a double coiled yarn actuator. First,each coiled yarn actuator was individually characterized in a three-electrodeelectrochemical system in an electrolyte. Next, the performance of the individualcoiled yarns was evaluated in presence of an anion-driven coiled yarn as counterelectrode. In the third step, the system was studied in a two-electrode system, andfinally, the overall performance was assessed in air using an ionogel. This studyoffers important insights into the working principles of double coiled yarnactuators and establishes the foundation for optimized designs of such actuatorsin air applications.

Hematopoietic stem cells (HSCs) are rare cells residing in the bone marrow and give rise to millions of new blood cells daily throughout life. Because of their multipotent, self-renewing nature, they have also been used for several decades to treat hematological disorders. However, HSCs are scarce and difficult to maintain ex vivo, demonstrating the need for developing novel in vitro methods to expand HSCs that mimic the complex in vivo microenvironment in suitable culture tissue plates, in extracellular matrix scaffolds, or on a biochip. One component to include in such an artificial microenvironment is HSC-related growth factors (GFs) immobilized on surfaces that mimic membrane-bound GFs in vivo. In this paper, we have initiated the development of an ex vivo system to study the immobilization of growth factors that sustain HSC maintenance and possibly expansion. However, since HSC-related GFs are expensive we have developed a proof-of-concept model using bovine serum albumin (BSA) as an alternative. Polypyrrole (PPy) was electrochemically synthesized in the presence of dicarboxylic acids with different hydrocarbon chain lengths and polycarboxylic acids with different molecular weights as dopants. BSA was immobilized on the PPy surface using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to couple BSA to the carboxylic acid dopant of PPy. These PPy films with different dopants showed different abilities to immobilize BSA using EDC/NHS coupling and also different surface properties. In addition, owing to the interesting switchable properties of PPy upon alteration of the oxidation/reduction potential, the immobilized BSA could change its presentation on the PPy surface depending on the redox state. To characterize the PPy surfaces and to study the different immobilization results of BSA on these PPy variants with different dopants and different presentation behavior upon redox switching, the electrochemical properties, hydrophobicity, thickness, roughness, surface COOH density and fluorescence labeling were investigated. The results indicate that the polycarboxylic acid dopants could immobilize more BSA on the PPy surface. Moreover, the BSA in the as-fabricated state shows a "collapsed" presentation on the PPy surface, a "less collapsed" presentation in the oxidized state and an "erected" presentation in the reduced state. Cell viability studies using hematopoietic cells showed that the developed PPy-BSA surfaces did not negatively alter cell viability or cell proliferation compared to the control.

In the fabrication of textile-based ionic EAP actuators, yarns are first coated with PEDOT by solution dip coating to make the passive yarns conductive. This is followed by PPy deposition to induce electrochemicaldrivenactuation. In these textile-based actuators, the performance of the actuators depends amongst others on the mechanical and electrical properties of the first conductive PEDOT coating layer. In this study 5different PEDOT solutions were prepared by adding different additives to poly(3,4-ethylenedioxythiophene) polystyrene sulfonate solutions. Films were formed from these solutions and their electrical conductivityand mechanical strength were measured. These solutions were then coated on polyamide multifilament yarns and dried at different temperatures, and their resistance and mechanical properties were measured. Theyarn coated with PEDOT:PSS-PG 90 weight percent exhibit the lowest Young's modulus 0.33 MPa at room temperature, while the yarn coated with PEDOT:PSS-PEG-DMSO exhibited the lowest resistance of 130 ohms at180°C. This study provides valuable insights that by tailoring the PEDOT solution composition and drying temperature the conductivity and mechanical properties of the coated yarn can be improved ultimatelypaving the way for better actuation performance of the textile-based ionic EAP actuators.

Smart textile actuators are gaining attention for applications in soft robotics and wearable electronics. These actuators can undergo controlled, reversible deformation in response to external stimuli like temperature changes or electric potential. Recent advancements focus on integrating smart yarns, fibre actuators, and functional materials directly in/on textiles. The mechanics of the textile substrate influence the actuation performance of these devices, which can enable complex movements. By using different weave patterns in combination with different yarns, the mechanical anisotropy of the substrate can be enhanced. Additive manufacturing offers a promising approach for fabricating these actuators, allowing rapid customization of active and passive material patterns. This study explores multi-layered PEDOT:PSS actuators 3D-printed onto various textile substrates via syringe-based extrusion. The effects of different weave patterns on bending actuation are examined, and the findings highlight the relationship between textile design, material composition, and fabrication methods in optimizing smart textile actuators.

Soft actuators are necessary for the development of soft robotics. While advances have been made in creating artificial means of motion with compliant materials, challenges remain. Within the area of electromechanically active polymers, forces are often small and limited to wet electrolyte conditions. Herein, textile logics and processes are employed to demonstrate woven, in-air operating, freestanding, soft textile actuators which can be electrically controlled. In-air actuating trilayer tape yarn consisting of poly(3,4ethylenedioxythiophene): polystyrenesulfonate layers and an ionogel are developed. The former acts as polymeric electroactive electrodes and the latter as a solid-state electrolyte, providing ions for the actuation. Weaving is used for creating bending fabrics, possible to post-process like any fabric. By weaving, actuator tape yarns are assembled in parallel to upscale the total output force, or alternated with non-actuating yarns to make passive and active areas. The weaving method also allows for additional yarn functionalities to be incorporated, e.g., to make conductive pathways, enabling multi-actuation areas, and individual electrical control. Additionally, tape yarns are arranged to create textile structures with both actuation and sensing. As a proof-of-concept, the developed fabric actuators enable novel wearable robotic devices for future applications that are inherently soft, lightweight, and multifunctional.

Smart textile actuators have garnered increasing attention owing to their versatile applications in soft robotics and wearable electronics. These actuators exhibit the capability to undergo controllable and reversible deformation in response to external stimuli such as temperature variations or electric potential. The latest evolution in smart textiles involves the integration of smart yarn- and fiber-actuators, as well as the incorporation of smart materials onto textile substrates. The underlying mechanics of the textile substrate play a significantrole in determining the overall performance of these actuators, offering opportunities to achieve intricate actuation modes effectively.

Moreover, the utilization of additive manufacturing techniques presents a promising avenue for the fabrication of these devices, enabling rapid customization and optimization of both active and passive material patterns to amplify their functionality. In this investigation, multi-layered PEDOTactuators were 3D printed on different textile fabrics using syringe-based extrusion, with the aim of investigating how different weave and knit patterns influenced actuation performance. Additionally, intricate patterns of passive materials were incorporated through printing methods, leveraging distributed compliance to program the movement capabilities of the actuators. This work sheds light on the interplay between textile substrate design, material composition, and fabrication techniques in enhancing the performance and functionality of smart textile actuators.

Intelligent fiber-elastomer composites and intelligent textiles are both active research areas in the fields of soft robotics and wearables. Tailored properties for these applications can be obtained by tailoring textile structures and fiber functionalities, such as integrated sensor or actuator properties. This work focuses on developing filamentary conductive polymer actuators for use in soft robotics or wearables. The actuators are based on wet-spun poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) fibers, with Polypyrrole (PPy) electropolymerized onto the PEDOT:PSS fibers surface. By varying the duration of PPy electropolymerization, and thus the thickness of the PPy coating, this study investigates its effect on the mechanical and actuation properties of the fibers. The developed actuator fibers achieve a repeatable high linear contractile elongation of up to 1.7%, tensile forces of about 100 mN, and mechanical stresses of about 1 MPa. Such properties make these fibers a compelling choice as a base material for textiles to be integrated into soft robotics and wearables.