Browsing by Author "Silva, Pedro E.S."

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Active Textile Fabrics from Weaving Liquid Crystalline Elastomer Filaments
(2023-04-06) Silva, Pedro E.S.; Lin, Xueyan; Vaara, Maija; Mohan, Mithila; Vapaavuori, Jaana; Terentjev, Eugene M.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Active fabrics, responding autonomously to environmental changes, are the “Holy Grail” of the development of smart textiles. Liquid crystal elastomers (LCEs) promise to be the base materials for large-stroke reversible actuation. The mechanical behavior of LCEs matches almost exactly the human muscle. Yet, it has not been possible to produce filaments from LCEs that will be suitable for standard textile production methods, such as weaving. Based on the recent development of LCE fibers, here, the crafting of active fabrics incorporating LCE yarn, woven on a standard loom, giving control over the weave density and structure, is presented. Two types of LCE yarns (soft and stiff) and their incorporation into several weaving patterns are tested, and the “champions” identified: the twill pattern with stiffer LCE yarn that shows the greatest blocking force of 1–2 N cm−1, and the weft rib pattern with over 10% reversible actuation strain on repeated heating cycles. Reversible 3D shape changes of active fabric utilize the circular weaving patterns that lead to cone shapes upon heating. The seamless combination of active LCE yarns into the rich portfolio of existing passive yarns can be transformative in creating new stimuli-responsive actuating textiles.
In-situ Monitoring of Photocontrollable Wrinkle Erasure in Azobenzene-based Supramolecular Systems
(2023-07-03) Dong, Yujiao; Silva, Pedro E.S.; Timonen, Jaakko V.I.; Vapaavuori, Jaana
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this contribution, dynamic photoinduced wrinkle erasure enabled by photomechanical changes in supramolecular polymer-azo complexes was characterized via confocal microscopy. Different photoactive molecules, disperse yellow 7 (DY7) and 4,4′-dihydroxyazobenzene (DHAB), were compared to 4-hydroxy-4′-dimethylaminoazobenzene (OH-azo-DMA). The characteristic erasure times of wrinkles were quickly assessed by using an image processing algorithm. The results confirm that the photoinduced movement on the topmost layer can be successfully transferred to the substrate. Furthermore, the chosen supramolecular strategy allows decoupling the effect of molecular weight of the polymer and photochemistry of the chromophore, allowing quantitative comparison of wrinkling erasure efficiency of different materials and providing a facile way to optimize the system for specific applications.
Light-Driven Multidirectional Bending in Artificial Muscles
(2024-09-19) Madani, Zahra; Silva, Pedro E.S.; Baniasadi, Hossein; Vaara, Maija; Das, Susobhan; Arias, Juan Camilo; Seppälä, Jukka; Sun, Zhipei; Vapaavuori, Jaana
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Using light to drive polymer actuators can enable spatially selective complex motions, offering a wealth of opportunities for wireless control of soft robotics and active textiles. Here, the integration of photothermal components is reported into shape memory polymer actuators. The fabricated twist-coiled artificial muscles show on-command multidirectional bending, which can be controlled by both the illumination intensity, as well as the chirality, of the prepared artificial muscles. Importantly, the direction in which these artificial muscles bend does not depend on intrinsic material characteristics. Instead, this directionality is achieved by localized untwisting of the actuator, driven by selective irradiation. The reaction times of this bending system are significantly – at least two orders of magnitude – faster than heliotropic biological systems, with a response time up to one second. The programmability of the artificial muscles is further demonstrated for selective, reversible, and sustained actuation when integrated in butterfly-shaped textiles, along with the capacity to autonomously orient toward a light source. This functionality is maintained even on a rotating platform, with angular velocities of 6°/s, independent of the rotation direction. These attributes collectively represent a breakthrough in the field of artificial muscles, intended to adaptive shape-changing soft systems and biomimetic technologies.