4D printing of wooden actuators: encoding FDM wooden filaments for architectural responsive skins

PurposeConventional motion mechanisms in adaptive skins require rigid kinematic mechanical systems that require sensors and actuation devices, hence impeding the adoption of zero-energy buildings. This paper aims to exploit wooden responsive actuators as a passive approach for adaptive facades with dynamic shading configurations. Wooden passive actuators are introduced as a passive responsive mechanism with zero-energy consumption.Design/methodology/approachThe study encodes the embedded hygroscopic parameters of wood through 4D printing of wooden composites as a responsive wooden actuator. Several physical experiments focus on controlling the printed hygroscopic parameters based on the effect of 3D printing grain patterns and infill height on the wooden angle of curvature when exposed to variation in humidity. The printed hygroscopic parameters are applied on two types of wooden actuators with difference in the saturation percentage of wood in the wooden filaments specifically 20% and 40% for more control on the angle of curvature and response behavior.FindingsThe study presents the ability to print wooden grain patterns that result in single and double curved surfaces. Also, printing actuators with variation in infill height control each part of wooden actuator to response separately in a controlled passive behavior. The results show a passive programmed self-actuated mechanism that can enhance responsive façade design with zero-energy consumption through utilizing both material science and additive manufacturing mechanisms.Originality/valueThe study presents a set of controlled printed hygroscopic parameters that stretch the limits in controlling the response of printed wood to humidity instead of the typical natural properties of wood.

Ultrarobust, tough and highly stretchable self-healing materials based on cartilage-inspired noncovalent assembly nanostructure

Self-healing materials integrated with excellent mechanical strength and simultaneously high healing efficiency would be of great use in many fields, however their fabrication has been proven extremely challenging. Here, inspired by biological cartilage, we present an ultrarobust self-healing material by incorporating high density noncovalent bonds at the interfaces between the dentritic tannic acid-modified tungsten disulfide nanosheets and polyurethane matrix to collectively produce a strong interfacial interaction. The resultant nanocomposite material with interwoven network shows excellent tensile strength (52.3 MPa), high toughness (282.7 MJ m‒3, which is 1.6 times higher than spider silk and 9.4 times higher than metallic aluminum), high stretchability (1020.8%) and excellent healing efficiency (80–100%), which overturns the previous understanding of traditional noncovalent bonding self-healing materials where high mechanical robustness and healing ability are mutually exclusive. Moreover, the interfacical supramolecular crosslinking structure enables the functional-healing ability of the resultant flexible smart actuation devices. This work opens an avenue toward the development of ultrarobust self-healing materials for various flexible functional devices.

A Theoretical Study on the Transient Morphing of Linear Poroelastic Plates

Based on their shape-shifting capabilities, soft active materials have enabled new possibilities for the engineering of sensing and actuation devices. While the relation between active strains and emergent equilibrium shapes has been fully characterized, the transient morphing of thin structures is a rather unexplored topic. Here, we focus on polymer gel plates and derive a reduced linear model to study their time-dependent response to changes in the fluid environment. We show that independent control of stretching and bending deformations in stress-free conditions allows to realize spherical shapes with prescribed geometry of the mid-plane. Furthermore, we demonstrate that tensile (compressive) membrane stresses delay (accelerate) swelling-induced shape transitions compared to the stress-free evolution. We believe that these effects should be considered for the accurate design of smart systems and may contribute to explain the complexity of natural shapes.

Morphic Arrangement of High Flexibility and Aspect Ratio Wing

Morphing of aerodynamic surfaces or conformal shape adaptation of aerodynamic surfaces can be used to control aircraft, utilized similarly as in nature, where insects and birds deform their wings to achieve a wide range of flight conditions. Morphing of wings has the potential to bring numerous advantages in flight performance in comparison to a rigid, conventional solution, that utilizes stiff aerodynamic surfaces. Reduction of parasitic drag due to the lack of gaps between the various moveable surfaces is one of them. Even so, a wing whose sections are able to deform independently or conform can better adapt to wide range of flight conditions than a rigid solution, or a solution based on conventional aerodynamic surfaces, such as flaps and ailerons. Additionally, the conformal shape adaptation or morphing of aerodynamic surfaces may lead to a potentially reduced weight and mechanical complexity, which may be achieved by utilizing wing deformations directly in the structure instead of connecting conventional actuation devices to the system. The aim of this paper is to propose a morphic arrangement of a high flexibility and high aspect ratio wing, that could be utilized in High Altitude Long Endurance aircraft, where the efficiency of the design is of utmost importance. A significant reduction of parasitic drag and reduction of weight is a promising basis for pursuing morphic and conformal shape adaptation designs. This paper qualitatively explores the space of morphic arrangements and conformal shape adaptation designs and utilizes inventive approaches to check and identify designs that may be promising. A wing design is proposed, that utilizes morphing of wing and conformal shape adaptation.

Structure and Dielectric Properties of Electroactive Tetraaniline Grafted Non-Polar Elastomers

Intrinsic modification of polybutadiene and block copolymer styrene–butadiene–styrene with the electrically conducting emeraldine salt of tetraaniline (TANI) via a three-step grafting method, is reported in this work. Whilst the TANI oligomer grafted at a similar rate to both polybutadiene and styrene–butadiene–styrene under the same conditions, the resulting elastomers exhibited vastly different properties. 1 mol% TANI-PB exhibited an increased relative permittivity of 5.9, and a high strain at break of 156%, whilst 25 mol% TANI-SBS demonstrated a relative permittivity of 6.2 and a strain at break of 186%. The difference in the behaviour of the two polymers was due to the compatibilisation of TANI by styrene in SBS through π-π stacking, which prevented the formation of a conducting TANI network in SBS at. Without the styrene group, TANI-PB formed a phase separated structure with high levels of TANI grafting. Overall, it was concluded that the polymer chain structure, the morphology of the modified elastomers, and the degree of grafting of TANI, had the greatest effect on the mechanical and dielectric properties of the resultant elastomers. This work paves the way for an alternative approach to the extrinsic incorporation of conducting groups into unsaturated elastomers, and demonstrates dielectric elastomers with enhanced electrical properties for use in actuation devices and energy harvesting applications.

Bioactuators based on stimulus-responsive hydrogels and their emerging biomedical applications

The increasingly intimate bond connecting soft actuation devices and emerging biomedical applications is triggering the development of novel materials with superb biocompatibility and a sensitive actuation capability that can reliably function as bio-use-oriented actuators in a human-friendly manner. Stimulus-responsive hydrogels are biocompatible with human tissues/organs, have sufficient water content, are similar to extracellular matrices in structure and chemophysical properties, and are responsive to external environmental stimuli, and these materials have recently attracted massive research interest for fabricating bioactuators. The great potential of employing such hydrogels that respond to various stimuli (e.g., pH, temperature, light, electricity, and magnetic fields) for actuation purposes has been revealed by their performances in real-time biosensing systems, targeted drug delivery, artificial muscle reconstruction, and cell microenvironment engineering. In this review, the material selection of hydrogels with multiple stimulus-responsive mechanisms for actuator fabrication is first introduced, followed by a detailed introduction to and discussion of the most recent progress in emerging biomedical applications of hydrogel-based bioactuators. Final conclusions, existing challenges, and upcoming development prospects are noted in light of the status quo of bioactuators based on stimulus-responsive hydrogels.

H.761 Support of a News input Node and a New "recognition" Node-Event to Enable Multimodal User Interactions

Multimedia languages traditionally, they focus on synchronizing a multimedia presentation (based on media and time abstractions) and on supporting user interactions for a single user, usually limited to keyboard and mouse input. Recent advances in recognition technologies, however, have given rise to a new class of multimodal user interfaces (MUIs). In short, MUIs process two or more combined user input modalities (e.g. speech, pen, touch, gesture, gaze, and head and body movements) in a coordinated manner with output modalities . An individual input modality corresponds to a specific type of user-generated information captured by input devices (e.g. speech, pen) or sensors (e.g. motion sensor). An individual output modality corresponds to user-consumed information through stimuli captured by human senses. The computer system produces those stimuli through audiovisual or actuation devices (e.g. tactile feedback). In this proposal, we aim at extending the NCL multimedia language to take advantage of multimodal features.