Search Results (7)

Flexible hydrogel sensors demonstrate emerging applications, such as wearable electronics, soft robots, and humidity smart devices, but their further application is limited due to their single-responsive behavior and unstable, low-sensitivity signal output. This study develops a dual-responsive starch-based conductive hydrogel via a facile “one-pot” strategy, achieving mechanically robust pressure sensing and ultra-sensitive humidity detection. The starch-Poly (2,3-dihydrothieno-1,4-dioxin)-poly (styrenesulfonate) (PEDOT:PSS)-glutaraldehyde (SPG) hydrogel integrates physical entanglement and covalent crosslinking to form a porous dual-network architecture, exhibiting high compressive fracture stress (266 kPa), and stable electromechanical sensitivity (ΔI/I₀, ~2.3) with rapid response (0.1 s). In its dried state (D-SPG), the film leverages the starch’s hygroscopicity for humidity sensing, detecting minute moisture changes (ΔRH = 6.6%) within 120 ms and outputting 0.4~0.5 (ΔI/I₀) signal amplitudes. The distinct state-dependent responsiveness enables tailored applications: SPG monitors physiological motions (e.g., pulse waves and joint movements) via conformal skin attachment, while D-SPG integrated into masks quantifies respiratory intensity with 3× signal enhancement during exercise. This work pioneers a sustainable candidate for biodegradable flexible electronics, overcoming trade-off limitations between mechanical integrity, signal stability, and dual responsiveness in starch hydrogels through synergistic network design. Full article

Hygroscopic seed-scale movement is responsible for the weather-adaptive opening and closing of pine cones and for facilitating seed dispersal under favorable environmental conditions. Although this phenomenon has long been investigated, many involved processes are still not fully understood. To gain a deeper mechanical and structural understanding of the cone and its functional units, namely the individual seed scales, we have investigated their desiccation- and wetting-induced movement processes in a series of analyses and manipulative experiments. We found, for example, that the abaxial scale surface is responsible for the evaporation of water from the closed cone and subsequent cone opening. Furthermore, we tested the capability of dry and deformed scales to restore their original shape and biomechanical properties by wetting. These results shed new light on the orchestration of scale movement in cones and the involved forces and provide information about the functional robustness and resilience of cones, leading to a better understanding of the mechanisms behind hygroscopic pine cone opening, the respective ecological framework, and, possibly, to the development of smart biomimetic actuators. Full article

Plant structures exhibit complex behaviors through unique shape changes and movements closely related to moisture factors. When the plants absorb moisture, their inside has a higher tension than their outside, so the entire structure is folded to closure or opened. The principle and property could be applied to bio-inspired technology, which is the process of fusion mimicking the structure, function, metabolism, mechanism, and ecological system of those creatures adapted to their environments. In this study, we analyzed the functions and physical characteristics of environment-sensing plants to demonstrate the principles of plants with opening-and-closing and curling-and-uncurling mechanisms and to better understand these behavior principles. From a biological and ecological viewpoint, the target sensory and cognitive plants that respond to external humidity and vibration were found to undergo structural changes in the size of the xylem and the degree of adhesion of the leaf and stem, as well as the opening, closing, and curling of the external shapes of the plants. The phenomenon of external form changes based on the microstructural characteristics of plants showed a promising direction for addressing issues in existing technology, such as non-powered operation. Therefore, in this study, we presented a biomimetic humidification model that was biocompatible and reversible. Pinecone samples with the applied opening-and-closing mechanism were to apply these biological properties to biomimetics. The results provide biomimetic knowledge for understanding the functions of biological and ecological features underlying the morphological changes in humidity-sensing plants and plant bioacoustics. These bio-inspired plant resources could provide sustainable new-growth power and valuable scientific information for advancing the research and technological development of biomimetics. Full article

To monitor dynamic ECG for a long time, fabric electrodes must have excellent comfort and electrical properties. In addition, the quality of the collected ECG should be as free as possible from interference by motion artifacts due to dry skin and body movement. This study explores the comfort of four different materials and structures of silver-plated fabric electrodes, analyzing the acquisition effect of ECG signals under dynamic and static conditions. To obtain fabric electrodes with good comfort levels and stable ECG signal monitoring under dynamic and static conditions, four kinds of electroless silver-plated conductive fabrics were selected and assembled into fabric electrodes. Permeability, electrochemical impedance spectrum, static opening voltage, and dynamic static electrocardiogram were tested and evaluated for each of the four fabric electrodes; additionally, the comfort of the four fabric electrodes and the mass of ECG monitored under dynamic and static conditions were assessed. The results showed that the highly hygroscopic knitted fabric electrode showed better comfort than the other three samples. The electrochemical impedance spectrum curve of the highly hygroscopic knitted fabric electrode was relatively smooth and stable, and it had lower impedance than the other electrodes; moreover, the static open-circuit voltage changed more stably with the increase of processing time compared to the other samples. The four kinds of fabric electrodes all collected clear and stable ECG in the resting state. However, in dynamic conditions, only the highly hygroscopic knitted fabric electrodes collected stable ECG under the conditions of seven daily life actions, clearly distinguishing between the P-wave, QRS wave group, and T-wave. The knitted fabric electrode has a high correlation with the ECG measured by a disposable gel electrode, meeting the standards needed to monitor ECG during the human body’s daily activities. Full article

Various mechanisms of plant organ movements have been reported, including the close association of two layers with expressed differences in hygroscopic properties. Following this principle, actuator beams composed of thin veneers out of normal and compression wood cut from Scots pine (Pinus sylvestris L.) were prepared by using two types of adhesives. The mismatch of the swelling properties of the two layers in tight combination resulted in an expressed bending deflection in response to set humidity changes. The resulting curvatures were measured and analyzed by the Timoshenko bi-metal-model, as well as with an enhanced three-layer model, with the latter also considering the mechanical influence of the glueline on the actuator bending. The thermally induced strain in the original model was replaced by another strain due to moisture changes. The strain was modelled as a function of wood density, along with changes in wood moisture. Experiments with free movement of the bilayer to measure curvature, and with constraints to determine forces, were performed as well. Deformation and magnitude of actuators movements were in close agreement with the enhanced bilayer-model for the phenol-resorcinol-formaldehyde adhesive, which deviated substantially from the casein adhesive glued actuators. The obtained results are seen as critical for wood-based actuator systems that are potentially used in buildings or other applications. Full article

The abstraction and implementation of plant movement principles into biomimetic compliant systems are of increasing interest for technical applications, e.g., in architecture, medicine, and soft robotics. Within the respective research and development approaches, advanced methods such as 4D printing or 3D-braiding pultrusion are typically used to generate proof-of-concept demonstrators at the laboratory or demonstrator scale. However, such techniques are generally time-consuming, complicated, and cost-intensive, which often impede the rapid realization of a sufficient number of demonstrators for testing or teaching. Therefore, we have produced comparable simple handcrafted compliant systems based on paper, wood, plastic foil, and/or glue as construction materials. A variety of complex plant movement principles have been transferred into these low-cost physical demonstrators, which are self-actuated by shrinking processes induced by the anisotropic hygroscopic properties of wood or paper. The developed systems have a high potential for fast, precise, and low-cost abstraction and transfer processes in biomimetic approaches and for the “hands-on understanding” of plant movements in applied university and school courses. Full article

In order to better understand the functions of plants, it is important to analyze the internal structure of plants with a complex structure, as well as to efficiently monitor the morphology of plants altered by their external environment. This anatomical study investigated structural characteristics of pinecones to provide detailed descriptions of morphological specifications of complex cone scales. We analyzed cross-sectional image data and internal movement patterns in the opening and closing motions of pinecones, which change according to the moisture content of its external environment. It is possible to propose a scientific system for the deformation of complex pinecone for the variable structures due to changes in relative humidity, as well as the application of technology. This study provided a functional principle for a multidisciplinary approach by exploring the morphological properties and anatomical structures of pinecones. Therefore, the results suggest a potential application for use in energy-efficient materials by incorporating hygroscopic principles into engineering technology and also providing basic data for biomimicry research. Full article