Browsing by Author "Yang, Jianfeng"

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    Dandelion-Inspired, Wind-Dispersed Polymer-Assembly Controlled by Light
    (WILEY-VCH VERLAG, 2023-03-03) Yang, Jianfeng; Zhang, Hang; Berdin, Alex; Hu, Wenqi; Zeng, Hao; Department of Applied Physics; Molecular Materials; Tampere University; Max Planck Institute for Intelligent Systems
    The rise of stimuli-responsive polymers has brought about a wealth of materials for small-scale, wirelessly controlled soft-bodied robots. Thinking beyond conventional robotic mobilities already demonstrated in synthetic systems, such as walking, swimming and jumping, flying in air by dispersal, gliding, or even hovering is a frontier yet to be explored by responsive materials. The demanding requirements for actuator's performance, lightweight, and effective aerodynamic design underlie the grand challenges. Here, a soft matter-based porous structure capable of wind-assisted dispersal and lift-off/landing action under the control of a light beam is reported. The design is inspired by the seed of dandelion, resembling several biomimetic features, i.e., high porosity, lightweight, and separated vortex ring generation under a steady wind flow. Superior to its natural counterparts, this artificial seed is equipped with a soft actuator made of light-responsive liquid crystalline elastomer, which induces reversible opening/closing actions of the bristles upon visible light excitation. This shape-morphing enables manual tuning of terminal velocity, drag coefficient, and wind threshold for dispersal. Optically controlled wind-assisted lift-off and landing actions, and a light-induced local accumulation in descending structures are demonstrated. The results offer novel approaches for wirelessly controlled, miniatured devices that can passively navigate over a large aerial space.
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    Feedbacks in light-active soft materials
    (SPIE, 2023-06-09) Yang, Jianfeng; Pi, Haotian; Zhang, Hang; Zeng, Hao; Department of Applied Physics; Rendina, Ivo; Petti, Lucia; Sagnelli, Domenico; Nenna, Giuseppe; Molecular Materials; Tampere University; Molecular Materials
    Imitating the self-regulated motions of natural species allows for novel applications in inanimate material systems. These applications include autonomous robotic systems, adaptive devices, and auto-energy harvesting. However, significant challenges exist in accurately controlling stimulus-induced deformations and establishing a reliable relationship between external energy fields and material deformations. In this study, we demonstrate that a simple light-triggered bending actuation in smart material systems based on liquid crystal elastomers is influenced by an opto-mechano-optical feedback mechanism. The pre-curved geometry enables enhance of light absorption upon photothermally induced deformation (from bent to flat), followed by a reduce of energy absorption upon further deformation (from flattening to bending toward the light). This strong nonlinearity in stimulus-induced deformability is governed by positive and negative feedback, and we experimentally verified these mechanisms using a thermal camera. Our results reveal the ubiquitous feedback nature of most light-active polymer systems.